Feasibility study of Li-Fe battery packs for a 12v car system

Feasibility study of Li-Fe batterypacks for a 12v car system

MASTER-THESIS

MA 709

written by

Gernot Hehn

Institut fur Elektronikder Technischen Universitat Graz

Leiter: Univ.-Prof. Dipl.-Ing. Dr.techn. Pribyl Wolfgang

in cooperation with

AMS Ag

Evaluator: Ass.Prof. Dipl.-Ing. Dr.techn Winkler GunterSupervisor at AMS: Dipl.-Ing. Manfreg Brandl

Graz, September 2012

1

Contents

1 Car Batteries 71.1 Typical Car 12V Electric System . . . . . . . . . . . . . . . . . . . . . . 71.2 Standard Car Batteries (wet cell lead-acid) . . . . . . . . . . . . . . . . 71.3 AGM Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.4 Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.4.1 Charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.4.2 Discharging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.5 Problems with Today’s System . . . . . . . . . . . . . . . . . . . . . . . 11

2 Li-Batteries 122.1 LiFePo4 Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122.2 Comparison with Lead Acid Batteries . . . . . . . . . . . . . . . . . . . 122.3 Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.3.1 Charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.3.2 Discharging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.3.3 Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3 LIN 183.1 Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.2 Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.2.1 Break Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193.2.2 Sync Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193.2.3 PID Protected IDentifier Field . . . . . . . . . . . . . . . . . . . 203.2.4 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203.2.5 Checksum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203.2.6 Frame Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203.2.7 LIN Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4 USB2LIN 234.1 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234.2 Choice of Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234.3 Schematic & Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234.4 Firmware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244.5 Bootloader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

5 LiFe Battery Management 265.1 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275.2 Choice of Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275.3 Schematic & Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305.4 LiFe Battery Management Firmware . . . . . . . . . . . . . . . . . . . . 30

6 PC-Software 36

7 Evaluation 397.1 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

7.1.1 Car Battery Setup . . . . . . . . . . . . . . . . . . . . . . . . . . 397.1.2 Lab Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

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Contents

7.2 Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427.3 Power Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457.4 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457.5 Safety Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467.6 Car Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

8 Conclusion 54

9 APPENDIX 559.1 USB2LIN Schematic and Layout . . . . . . . . . . . . . . . . . . . . . . 559.2 LiFe Battery Management Schematic and Layout . . . . . . . . . . . . . 559.3 3D Drawing of the Retrofit Battery . . . . . . . . . . . . . . . . . . . . . 55

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Contents

EIDESSTATTLICHE ERKLARUNG

Ich erklare an Eides statt, dass ich die vorliegende Arbeit selbststandig verfasst, andereals die angegebenen Quellen/Hilfsmittel nicht benutzt und die den benutzten Quellenwortlich und inhaltlich entnommenen Stellen als solche kenntlich gemacht habe.

Graz, am September 20, 2012 . . . . . . . . . . . . . . . . . . . . .

(Unterschrift)

Englische Fassung:

STATUTORY DECLARATION

I declare that I have authored this thesis independently, that I have not used other than the

declared sources / resources and that I have explicitly marked all material which has been

quoted either literally or by content from the used sources.

September 20, 2012 . . . . . . . . . . . . . . . . . . . . . . . .

(signature)

4

Abstract

Vehicle electronics have been hugely influenced by the enormous advantages that have beenmade in the fields of electronic and microelectronics. New appliances like climate controlvehicle safety systems (ABS/ESP/. . . ), modern route and navigation systems, on board en-tertainment and passenger comfort applications have increased the demand for power and en-ergy in cars dramatically. Adding to these new environmentally driven trends like start/stop,regenerative breaking, electrical power steering and mild hybrid solutions are increasing thedemand for energy even more. The load on a modern mid to high end limousine powersystem has reached levels that will wear out the battery in an unsatifactorily short time. Tar-geting these problems two solutions are presently discussed by the big German automotivecompanies. Either a higher voltage (preferrably 48V) board net is implemented, partiallysubstituting the classic 12V net, or the battery chemistry is changed towards a more robustand cycle resistant LiFePO4 system.

This thesis will evaluate the viability of the second solution. The goal is to enable under-standing of the differences in battery chemistry, why they help target today’s problems, andto explain necessary changes in the cars system to make the transistion. It will also propose abattery management system that performs all the necessary operations to keep the Lithiumbattery within its operating conditions. The last chapter will outline the practical evalua-tion of this system in a real world application and show how well the new system performscompared to a classic lead-acid battery system.

5

Zusammenfassung

Die Fahrzeugelektrik wurde enorm beeinflusst durch die Fortschritte in den Feldern Elek-tronik und Mikroelektronik. Neue Zusatzausstattungen wie Klimaanlage, Sicherheitssysteme(ABS/ESP/. . . ), moderne Navigationsgerate, integrierte Entertainment Systeme und Ap-plikationen fur den Fahrerkomfort haben die Energie und Leistungsanforderungen in Au-tos drastisch erhoht. Zusatzlich zu diesen Systemen haben auch durch Umweltbewusst-sein getriebene Trends wie start/stop Automatik, regeneratives Bremsen, elektrische Serv-olenkung und mild Hybrid Antriebe den Bedarf an elektrischer Leistung im Auto weiter indie Hohe geschraubt. Die elektrische Last in einem modernen Mittel- und Oberklassewagenhat einen Bereich erreicht in dem eine klassische Batterie in unzulanglicher Zeit ihre Funk-tion aufgibt. Um diese Probleme in den Griff zu bekommen werden derzeit zwei Losungenvon den deutschen Automobilkonzernen diskutiert. Entweder ein Bord Netz mit hohererSpannung (vorzugsweise 48V) wird implementiert das die Aufgaben des 12V Netzes zum Teilubernimmt, oder die Batteriechemie wird geandert, zu einer LiFePO4 Chemie mit wesentlichbesserer Zyklenfestigkeit und Hochstromeigenschaften. Diese Arbeit wird die Machbarkeitder zweiten Losung beleuchten. Ziel ist es das Verstandnis fur verschiedene Batteriechemienaufzubauen und zu zeigen warum mit diesen die heutigen Probleme gelost werden konnen.Auch die notigen Anderungen, die fur diese Umstellung am Auto selbst vorgenommen wer-den mussten, werden besprochen. Diese Losung wird anhand eines Batterie ManagementSystems, welches alle notwendigen Operationen beherrscht um eine Lithium Batterie inner-halb ihrer Operationsbedingungen zu betreiben, beleuchtet. Das letzte Kapitel wird sichmit der Evaluierung diese Systems in einem handelsublichen Fahrzeug auseinandersetzen unddabei einen Vergleich zu herkommlichen Losungen bieten.

6

1 Car Batteries

1.1 Typical Car 12V Electric System

The typical electric system in today’s car would look somewhat like Figure 1.1 The alternator,which is directly coupled to the engine block, will supply a uniform 12V net. The battery willbe charged until it reaches a defined maximum voltage. A control unit within the alternatorwill regulate its exciting current so that the output voltage won’t surpass a level of 13.8 ≈14.4V . With the application of a Battery management system and the knowledge about theState of Charge (SOC) of the battery it has become possible to only charge the battery whennecessary or in desired conditions (regenerative breaking for example). This also allows to stopcharging the battery when the motor power is needed elsewhere (for example in accelerationphases).

Figure 1.1: Typical car battery system

1.2 Standard Car Batteries (wet cell lead-acid)

The car battery most commonly used today is a ”flooded cell” wet type lead-acid battery.The battery consists of 6 serially connected primary lead acid-cells with a typical voltage of2V each. A single cell typically consists of a negative electrode made of spongy or porouslead, the positive electrode made of lead oxide and an electrolyte made out of 35% SulfuricAcid and 65% water. Additionally there is a permeable separator separating the electrodes tostop them from accidentially connecting. As the name of the battery suggests both electrodesare submerged in the electrolyte. The chemical reaction that allows these batteries to workis as follows:

Overall reaction:

PbO2 + Pb + 2 H2SO4

discharge−−−−−−−−−−−−−−charge

2 PbSO4 + 2 H2O

At the negative terminal:

Pb + SO2−4


PbSO4 + 2 e−

7

1 Car Batteries

At the positive terminal:

PbO2 + SO2−4 + 4 H+ + 2 e−


PbSO4 + 2 H2O

1.3 AGM Batteries

AGM (Absorbed Glass Mat) batteries belong to the group of VRLA (Valve Regulated LeadAcid), ”sealed” or ”maintainance free” batteries. AGM batteries use a very fine fiber Boron-Silicate glass mat seperator to immobilize the sulfuric acid in the battery. This type of batterywas invented for military applications in the 80’s. The main advantages compared to a classiccar battery are

• Lower self discharge rate

• Higher number of charge cycles

• Less capacity degradation

• Safer than wet batteries

• Virtually maintainance free

• Can withstand hazardous environments better

Their main disadvantage is that they are more expansive (≈ 20−30%) compared to standardbatteries.

However car manufacturers tend to use these kind of batteries in modern cars featuringStart/Stop to get acceptable lifetimes.

1.4 Handling

Like all batteries lead-acid batteries have special requirements concerning their operation.These can be split into charging and discharging conditions.

1.4.1 Charging

As Figure 1.2 shows there are 4 distinct phases in the charging process

1. Bulk Charge or CC (Constant Current) mode:

In this mode the battery is somewhere between 30% and 80% SOC (discharge below30% SOC will damage the battery permanently) The charger applies a constant currentsomewhere between 1

10and 1

3of the battery’s capacity. The voltage climbs to a level

called the ”quick charging voltage”. This phase is where most charge is absorbed bythe battery in the shortest amount of time.

2. Absorbtion Charge or CV (Constant Voltage) mode:

In this mode the battery receives another 15% of charge. This phase is qualified bythe constant voltage applied to the battery. The current drawn by the battery slowlydecreases due to the chemical process in the battery coming close to equilibrium.

3. Equalization Charge Mode:

In this mode a modest constant current in the range of 5% to 10% is applied to pushthe battery to the gasing phase on purpose. This mode helps to deliver the remaining5% of capacity into the battery and to equalize the charge between the 6 cells in atypical system. This phase is typically not used in automotive application as gasing is

8

1 Car Batteries

Figure 1.2: Diagram of the 4 lead-acid battery charging phases [24]

highly undesired in a car (the gas consists of elementar Hydrogen and Oxygen and ishighly explosive).

4. Float Maintenance Charge Mode:

This mode is only used in charging systems for battery storage. Typically a very smallcurrent in the 50 to 100mA range is applied to compensate the battery’s self dischargeprocess. This mode is not implemented in a car system as there is no power sourceother than the battery to charge from during the time the car is parked.

1.4.2 Discharging

Like every chemical process the discharging process of a lead acid battery is dependent on thetemperature at which the reaction takes place, the concentration of the active partners in theelectrolyte and the rate of Ion transfer (ie. the amount of current drawn from the battery)

This leads to the discharge performance of a Lead-acid battery being significantly dependenton

• Discharge current relative to the total capacity of the Battery (C-rating)

• The percentage of capacity used during a cycle (aka. cycle depth)

• The temperature of the battery during discharge

This means that the amount of charge the battery is able to deliver as well as the number ofcycles the battery is able to endure is dependent on those parameters.

A dependence which is illustrated in Figure 1.3 through 1.5

9

1 Car Batteries

Figure 1.3: Influence of the discharge current on the usable capacity [5]

Figure 1.4: Influence of the discharge current on the usable capacity [4]

10

1 Car Batteries

Figure 1.5: Influence of the discharge current on the cycle life [5]

1.5 Problems with Today’s System

A classic car system typically used its battery only once per drive to start the motor andsupply power to lights etc. when the car was parked. In a modern car system the load onthe battery is mounting drastically due to the increased number of electrical appliances. Inaddition to that a start stop automatic makes it necessary to cycle the battery more thanonce during a drive cycle and use a higher percentage of its capacity. This leads to thebattery beeing constantly in a charge state somewhere around 50% SOC rather than beingfully charged most of the time as this was the classic case.

This leads to early battery failures in the field and the necessity to change batteries moreroutinely than it was the case before.

11

2 Li-Batteries

”One of the important things to understand about lithium batteries is that the term ’LithiumBattery’ summarises a whole lot of different battery chemistries. In fact the technology inthis field is still changing, so I can’t even give a full overview of the existing technologies.”[23]

In this text I will focus on the LiFePo4 type of batteries and the differences in handlingcompared to lead acid batteries to point out the problems and advantages arising from thischange in battery chemistry.

2.1 LiFePo4 Batteries

To start off let us have a look at a LiFePo4 Cell and what it is made of.

This type of cell consists of a cathode made out of LiFePo4 material, an anode of graphite orhard carbon and a lithium ion conducting electrolyte, usually an organic solvent mixed witha lihium salt. The chemical reaction taking place in such a battery is as follows:

LiC6(s) + Fe3+PO4


6 Cs + Li+Fe2+PO4(s)

2.2 Comparison with Lead Acid Batteries

The table 2.1 gives a good overview of the difference in properties between lead acid batteriesand LiFePo4 batteries. I have added the LiCoO2 type of lithum batteries for comparison.This is the type used in most modern computers and cell phones. Although these cells have aneven higher energy density, they are not considered for automotive application since they arenot intrinsically safe and suffer from a process called thermal runaway. This process can leadto an explosive decomposition of the battery when overcharged, which has led to a lot of recallsof batteries where the protection mechanism wasn’t adequate [19] & [18]. Needless to saythat such an instable nature disqualifies these batteries for usage in automotive applications.

Summarized the main advantages of LiFe batteries are the following:

• ≈ 4 times higher cycle life

• ≈ 3 times the energy density which is shown in Figure 2.1

• Very flat voltage curve 2.2

• High charge rates

• Low self discharge

• Unlike lead acid batteries, can be left in a partially discharged state for extended periodswithout causing permanent damage

• Maintenance free for the life of the battery

• Can be operated in any orientation

• No heavy metals used

In contrast these new batteries also have the following disadvantages:

12

2 Li-Batteries

Figure 2.1: Comparison of energy density of various battery types [20]

Figure 2.2: Comparison of discharge curves of various battery types [7]

13

2 Li-Batteries

• ≈ 2 - 3 times the costs

• Problems with low temperatures

• More critical in over and undercharge conditions

Battery Type Lead Acid LiFe LiCoO2

Commercialisation 1881 2002 1990Cell Voltage [V] 2 3,2 3,7

Energy by Weight [Wh/Kg]: 30-40 90-110 130-200Specific Power [W/Kg] 180 300 250 - 340

Energy by Volume [Wh/L] 60-75 220 340-400Max charge rate 1C 3C 5C

Continous discharge rate 3C 3C-10C 10C-30CPeak discharge rate 10C 10C-30C 30C-70C

Recharge Time ≥ 10 Hours 1 Hour 15min - 1hourCycle Life [Cycles] 500 - 800 2000 - 3000 500-1000

Self Discharge per month 5%-25% ≈ 3% ≈ 5Temp Range [C] -15 to 40 0 to 45 0 to 45

Preferred Charge Method CC/CV CC/CV CC/CVAverage Energy Cost [$/kWh] $100 $300 $200

Size [%] 100 75 30Weight [%] 100 35 25

Table 2.1: Comparison of Lead Acid and Lithium cells

2.3 Handling

As discussed in the disadvantage section above, Lithium based batteries are very susceptibleto over- and underload conditions. This requires the usage of specialised electronics whichkeeps the batteries within their specified parameters under all conditions. We can summarizethe tasks such an electronic has to fulfill as:

• Measure the pack voltage

• Measure the individual cell voltages

• Do a plausability check of pack voltage versus sum of cell voltages

• Measure the current being charged into or discharged from the battery

• Measure the temperature of the battery stack

• Try to equalize the charge between the different cells of a stack

• Compare the measured values against the maximum ratings described by the batterymanufacturer

• If any of the values is out of spec, disconnect the battery immediately

• Try to estimate the amount of charge still available in the battery

• Report the battery status and the system status to the ECU (typically via a LINinterface)

2.3.1 Charging

The charging system used for Li-type batteries is the CC (Constant Current)/CV (ConstantVoltage) system. This is the same as the first two phases in a lead acid charging process.

14

2 Li-Batteries

The third phase may never be used due to the reaction of lithium batteries to overchargeconditions and the fourth phase is mostly unnecessary due to the low self discharge rate thatall lithium batteries have in common. A typical charging curve (taken form the datasheet[6]) is shown in Figure 2.3

Figure 2.3: Plot of charging operation

2.3.2 Discharging

As with lead acid batteries the discharging characteristics hugely depend on current consump-tion (Figure 2.4) and temperature (Figure 2.5) as well as aging effects and the SOC.

These effects have to be addressed by the battery management in order to allow safe operationof the battery in its final application.

2.3.3 Balancing

Balancing is the process we use to equalize the charge of individual cells within a batterypack. There are a couple of different topologies in use to achieve these goals. [23] gives agood overview of the various possibilities. In this work I will however concentrate on activebalancing using an inductive coupler to transport charge between various cells. As discussedin section 5.2 we are using an AS8505 chipset to enable this functionality. A block diagramof this chipset can be seen in Figure 2.6.

15

2 Li-Batteries

Figure 2.4: Plot of discharging operation at various discharge rates

Figure 2.5: Plot of discharging operation at various temperatures

16

2 Li-Batteries

Figure 2.6: Block diagram of the AS8505/06 chip including peripheral components

17

3 LIN

3.1 Basics

‘LIN (Local Interconnect Network) is a concept for low cost automotive networks, whichcomplements the existing portfolio of automotive multiplex networks.’[21]

LIN is a single wire serial communication bus that was mainly developed for automotiveapplications which don’t require the complexity and speed of CAN and want to profit froma cost effective simple solution. The main benefits of the LIN architecture are:

• one master multiple slave network

• low cost implementation using standard uart (Universal Asynchronous Receiver Trans-mitter) hardware

• possibility to synchronize slaves that don’t have a stable clock source

• low cost single-wire implementation

• speed up to 20 kbit/s.

In the LIN Interface the master has control over all bus functions. It initializes transfersto and from the slaves and manages the bus activity schedule. The slave waits for its PID(Protected IDentifier) and responds with a pre defined answer.

Figure 3.1: Typical LIN network

18

3 LIN

3.2 Protocol

Figure 3.2: LIN Frame

The LIN Protocol describes a LIN frame consisting of

• Break field

• Sync field

• PID

• 1-8 bytes of data

• Checksum

The first three items are considered to be the header and are always sent by the master. Thedata bytes and checksum are the slaves response to the master request. LIN protocol definesan LSB first bit order. We will now take a look at the function of each item

3.2.1 Break Field

The break field stands at the beginning of each LIN communication. It is essential to signalthe beginning of a new transmission and to wake up all devices connected to a LIN Bus (ifthey are in sleep mode). The break field shall be at least 13 nominal bit times of dominantvalue (low voltage) followed by a break delimiter as shown in Figure 3.3 The slave node shalluse a threshold of 11 slave bit times to detect the break field in order to allow for clockvariations.

Figure 3.3: LIN Break field

3.2.2 Sync Field

The Sync field always transmits the data value 0x55 and is used to calibrate the bit clock ofthe slave with the master. This is essential if the slave uses a cheap low accuracy rc oscillator.Modern microcontrollers have integrated hardware that auto detects the sync field and makesthe baud (data transfer rate) calibration easier.

19

3 LIN

Figure 3.4: LIN Sync field

3.2.3 PID Protected IDentifier Field

The protected identifier consists of the frame identifier (Bits 0 to 5) and two parity bits (6and 7). ID Values 0 to 59 are used for signal carrying frames, 60 and 61 for diagnostic framesand configuration data 62 and 63 are reserved.

The Parity calculation works as follows:

P0 = ID0⊕ ID1⊕ ID2⊕ ID4

P1 = ¬(ID1⊕ ID3⊕ ID4⊕ ID5)

The mapping of the PID frame is shown in Figure 3.5

Figure 3.5: LIN PID field

3.2.4 Data

The Data frame carries between 1 and 8 bytes of data. Data is always transported LSB first.This also applies to data fields that span over multiple bytes. The LSB is always transmittedin the byte that is sent first.

3.2.5 Checksum

The last Field of a LIN transmission is always a Checksum. According to the new LIN2.2 specification, the Checksum is calculated over the data bytes as well as the PID. Thechecksum is an inverted eight bit sum with carry. For example if we transmit the followinginformation: PID=20 Data1 = 80 Data2 = 200 Data3 = 14 we would get

20 + 80 + 200 + 14 = 314− 255 = 59

¬59 = 196

So the checksum would be 196. The receiver checks this by adding the PID and Data fieldsand the Checksum. The result should always be 0xFF.

3.2.6 Frame Types

The LIN protocol distinguishes between three types of frames

• Unconditional Frame

• Event triggered Frame

• Sporadic Frame

20

3 LIN

Unconditional Frames are in the PID range between 0 and 59. The header is transmittedby the master in the allocated time slot. The response of the slave shall be immediate. Allsubscribers to this frame will receive it and make it available to their application.

Event triggered Frames are used to request data from slaves only in case the data has changed.Subscribers to this frame only respond if the requested value has changed since the lastrequest.

In addition to these frames, Diagnostic Frames (with PID 60 and 61) carry a special transportlayer and are used for in-system diagnosis and calibration.

3.2.7 LIN Schedule

The master has knowledge about all PIDs used in this particular network. It uses a prede-fined schedule table to request data from the slaves and makes these data available to theapplication. The default flowchart for such a schedule looks like this:

Figure 3.6: LIN Master Task [21]p.41

For our purpose we did not implement a schedule table into our LIN master as can be seenin the software flowchart 4.1 and rather let the application running on the PC decide whenand which PID is going to be sent. This makes the overall software design easier and allowsfor more flexibility during testing, furthermore we do not need scheduling since there is onlyone LIN slave in this particular network.

21

3 LIN

The LIN slave on the other hand has to follow a procedure shown in Figure 3.7

Figure 3.7: LIN Slave Task [21]p.43

The implementation of this behavior is discussed in detail in the Firmware section 5.4.

22

4 USB2LIN

In order to test the functionality of the whole platform in general and the LIN system indetail and to create a user friendly way to access the module data on a computer a smallUSB to LIN interface was developed.

4.1 Operation

This system uses the power of a modern PIC 18f14K50 microcontroller to implement a fullyUSB compatible PC Interface that is represented as a virtual COM PORT on PC side andthe AS8530 LIN SBC to provide a standard compatible LIN interface.

In Figure 9.1 you can see that this chip is powered by an AS1340 DC/DC converter whichprovides the 12V supply necessary for correct LIN operation. The switch S2 allows forsystem reset as well as for the possibility to update the firmware via an integrates USB HIDbootloader. For system diagnosis two LEDs are placed which display the status of the board(connected/driver installed/operational).

4.2 Choice of Components

Microcontroller: The PIC 18F14K50 was chosen for its integrated hardware USB slave func-tionality and LIN Interface. Good application support for both these Interfaces is also pro-vided by Microchip.

Lin System Basis Chip: The AS8530 is a house internal LIN SBC. It provides the necessarylevel translations for the 12V LIN interface as well as load dump and ESD protection. It alsoallows for remote wakeup via LIN.

Dc/Dc: The AS1340 high efficiency DC/DC converter uses an internal 1.4A MOSFET toreduce the external part count and makes the small board layout possible.

4.3 Schematic & Layout

Schematic 9.1 and Layout9.2 can be studied in the Appendix section of this document. P1is a connector to the TTL compatible UART/LIN Interface of the microcontroller, whichallows easy observation of the LIN Bus through a logic analyzer. P2 is the connector to theLIN Interface. It also outputs the 12V power rail which can supply up to 200mA of powerto a slave application. Remember however that there is no short circuit protection, so theUSB port of your computer might get damaged in an overload condition. J3 is a PicKitcompatible header to allow direct programming and debugging of the PIC controller. If thePic programmer is used to upload firmware directly, you will however lose the Bootloaderfunctionality. It is worth noting that the LIN interface is ESD protected by the internal ESDprotection of the AS8530 chip, however the USB interface does not sport any ESD protectionother than that of the microcontroller itself.

Additionally I want to give a short connector pin listing starting from left to right with theUSB connector facing to the left side and the populated side of the board facing upwards.

PGC|PGD|GND|VCC|MCLR RX|GND|TX GND|LIN|12V

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4 USB2LIN

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(1B

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]

PID

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[mA

] (3

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mV

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emp

erat

ure

[°C

/10

] (2

Byt

e)

PID

: 0x2

2C

ell 1

[m

V]

(2B

yte)

Cel

l 2 [

mV

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[m

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(2B

yte)

Cel

l 4 [

mV

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PID

: 0x2

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[uA

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(4B

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edan

ce [

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np

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err

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ime

Figure 4.1: USB2LIN Software Flowchart

24

4 USB2LIN

As one can see in Figure 4.1 the software flow of the USB2LIN Interface is based arounda virtual serial port presented to the PC side. This port allows connection with any soft-ware capable of serial communication with communication settings 115200kBaud 8N1. Afterconnection to a USB port the USB2LIN Firmware awaits the entry of a human readablecommand. The Firmware will accept either a ”p” [ASCII: 0x70] data package query followedby a hex number between 0 and F and upon reception it will start to request the informationassociated with this PID or and ”s” [ASCII: 0x73] followed by a hex number between 0 andF which will prompt it to send the according Command PID in the range of 0x10 to 0x1F.Upon reception of the slave answer it will check the data for integrity with the help of theLIN checksum and report it back to the PC via the virtual serial interface as human readableASCII data. In case of an error the Interface will try to resend the command up to threetimes. If this doesn’t work, it will report an error to the host with the string ”er”.

4.5 Bootloader

The PIC18 Microcontroller is programmed with the microchip HID-Bootloader available aspart of the Microchip Application Libraries[22] After installation of this package the nec-essary software can be found under ”Microchip Solutions v2012-12-05\USB\Device - Boot-loaders\HID \HIDBootloader (Windows).exe” This program will allow you to upload newfirmware to the microcontroller in use via the USB connection and an easy to use graphicalinterface.

To upload new firmware perform the following steps:

1. Start the HIDBootloader according to your operating system

2. Press the button on the USB2LIN board

3. While pressing the button connect the board to the USB interface of the Computer

4. The Bootloader software will recognize the attached board and display ”Device at-tached”

5. Click the ”Open Hex File” button and select the new firmware file

6. Click the ”Program/Verify” button. This will program the new firmware

7. After successful flash operation (as in Figure 4.2) disconnect the board from USB andthen reconnect it

8. The new Firmware should now be in operation

Figure 4.2: HID Bootlader after successful flashing operation

25

5 LiFe Battery Management

As was discussed in the section about Battery technologies the usage of lithium based batteriesnecessitates the installation of a battery management system. In the following chapter I willintroduce a concept for a system that provides all the features required to safely operate aLiFePo4 Battery in a car environment.

The main design concerns for such a system were:

• Accuracy

The system has to achieve an accuracy of <10mV and <100mA over the whole auto-motive temperature (-40 - +125C) range and the complete voltage and current rangeof the batteries

• System Safety

The system has to be able to detect malfunctions and react to them accordingly.

• Processing Power

For the implementation of a complex battery model, which is essential for good SOC/SOHestimation, a fast processor is required to compute the mathematical model within anacceptable time frame

• Power consumption

The targeted power consumption in standby mode was 100µA for the whole system.

26


5.1 Block Diagram

The Block diagram (Figure 5.1) gives a good overview of the interaction of the differentfunctional blocks in use. The batteries are connected to the AS8515 ADC chip as well asthe AS8506 balancing chip. These two ICs supply most of the functionality required in thissystem. A battery disconnect switch and a 100 µΩ Shunt are connected in series with thepower path of the battery, which is available at two pole plugs on the top of the case likein a classic lead acid battery. USB and JTAG connectivity have been implemented to makethe debugging process easier. However the production version would obviously only have theLIN connection to communicate with the ECU.

5.2 Choice of Components

Microcontroller:Since the trend in Battery Management Solutions points towards ever more complex math-ematical models for the battery chemistry and behavior, the major decision factor for themicrocontroller used was to supply enough power for such a model in a small affordable pack-age. The ARM Cortex M Series of microcontrollers is gaining widespread acceptance in thedeveloper community due to the possibility of choosing from a number of different develop-ment and debugging tools and the possibility to change chip manufacturers whilst staying inthe same architecture. The microcontroller of our choice is the Fujitsu MB9AF312K[9]. Itbelongs to the FM3 Series of Fujitsu microcontrollers which are based on the ARM Cortex-M3architecture and sport a wide variety of peripheral units. With 128Kbyte of Flash storagefor program data and 32Kbyte of Work Flash, a maximum operating Frequency of 40MHz,a number of peripheral functions including LIN,USB and multiple SPI interfaces in a small48pin LQFP package, it is well equipped to serve as the processing unit in this device.

Data acquisition + System Basis Chip:To measure total current, four cell voltages, total pack voltage and temperature the systemis using the AS8515 IC[3]. This chip provides two independent ADC channels with pro-grammable gain amplifiers to support a wide measurement range. Measurement of batteryvoltage is supported through resistive attenuator with disable function for power saving instandby. After analog to digital conversion and digital filtering, the resulting digital valuesare accessible through 4-wire serial interface. The device is powered directly from the batterythrough an integrated linear regulator and provides a 3.3V supply for the microcontroller.Additionally the IC integrates a LIN 2.1 transceiver which is used as the main communicationinterface in this application.

Active Balancer:The balance portion of the circuit is handled by the AS8506[2] active balancing IC. This chipssupports balancing up to 7 cells via integrated transmission gates and an external flybacktransformer which is commutated via the chip. The balancing decision is made by simulta-neous comparison of all cell voltages against an internal or external reference voltage. Cellswhich are below reference/average will receive charge packages from the external transformer.Communication with the microcontroller is handled via a 4 wire serial interface as well as theBalance done, Cell Voltage NOK, Wake and Trigger signals.

Voltage Level TranslatorTo translate the logic signals between the 5V domain used by the active balancing circuit andthe 3.3V domain used by the rest of the circuit a ”TI TXB0108 8-BIT BIDIRECTIONALVOLTAGE-LEVEL TRANSLATOR WITH AUTO-DIRECTION SENSING AND ±15− kVESD PROTECTION”[13] chip was used. The auto direction sensing feature comes in handysince we need to translate signals in both directions and didn’t want to use two chips. Addi-tionally the chip features a very low power consumption of just 4µA

Flyback TransformerIn order to operate the active balancing we need a flyback transformer that translates the

27


AS

851

5A

DC

4 t

o 1

M

UX

10

0 μΩ

Sh

un

t

Sen

se C

ell

32-b

itF

ujit

su-F

M3

Mic

roco

ntr

olle

r

AS

850

6A

ctiv

e-B

alan

cin

g-I

C

3,3V

/ 5V

Lev

el S

hif

ter

SPI + lin

SPI + Status signals

Sen

se V

bat

BatteryDisconnect

Switch

Su

pp

ly O

ut

Su

pp

ly V

bat

3,3V

3,3V

SP

I + S

tatu

s si

gn

als

5VV

ref

in

Fly

bac

k C

on

vert

er

Figure 5.1: Battery Management Hardware Block Diagram

28


≈ 12.8V pack voltage to a single cell voltage between 2.0V − 3.8V . The typical output cur-rent should be in the range of 100mA. So we can start with the following design considerations:

Uin/nom = 12.8V Uout = 3.8V Iout = 0.1A f = 100kHz wr(windingratio) = 1 duty = 25%

The minimum required inductance required for continuous mode operation is given by theformula:

L =T ∗ wr2 ∗ U2

in ∗ Uout

2 ∗ Iag ∗ (Uout + wr ∗ Uin)2

where Iag is given by

Iag =∆I

2∗ toff

T= frac0.12 ∗ 0.75 = 0.0375A

With this information we can calculate the required inductance to be at least

L =1E − 5 ∗ 1 ∗ 12.82 ∗ 3.8

2 ∗ 0.0375 ∗ (3.8 + 1 ∗ 12.8)2= 83.42µH

For our tests we used a Wuerth WE-FLEX[16] 749196111 type transformer. This transformerhas 6 individual windings that can be connected in parallel or series. Our configuration uses3 windings in series for both primary and secondary side, giving as a 1:1 winding ratio andan inductance of 246µH. Since this is about triple the inductance necessary for continuousoperation we decrease the current ripple to

Iag =T ∗ wr2 ∗ U2

in ∗ Uout

2 ∗ L ∗ (Uout + wr ∗ Uin)2= 0.0136A

and a typical current ripple of

∆I =2 ∗ Iag ∗ ttoff

= 0.036A

In the real application however we had to increase the duty cycle to 35 to 40% to achieve the100mA continous charge output into the battery, as can be seen in Figure 5.2

Figure 5.2: Secondary current of the flyback transformer

29


ESD ProtectionESD protection was added to the USB port to protect from problematic discharges in theenvironment of a car whilst driving. The protection device of choice was a ST USBLC6-2[15]. It offers a two data line protection with very low capacitance and is available in a tinySOT23-6L package.

5.3 Schematic & Layout

Schematic 9.1 and Layout 9.2 can be studied in the Appendix section of this document. Atthis point I want to emphasize the crucial ideas that influenced this design and what impactthey have on system performance.The board is split into two sections. On the right hand side you can see the balancingsubsection comprised of the AS8506, the flyback transformer and a few necessary passivecomponents. On the left hand side we have the AS8515 placed directly overhead the currentmeasurement, alongside the Fujitsu microcontroller and close to the 5pin battery connection,the multiplexer. The reason for this split was to make these parts easily discernible as theboard will be used for demonstration purposes at ams. For low offset measurements thisdesign has to observe the following rules for the AS8515:

• The placement of the AS8515 should be as close as possible to the shunt (for a goodthermal coupling and to keep the traces as short as possible)

• The traces leading to the shunt may not be coupled to the ground plane, instead theyshould be connected to the center point of the shunt solder connection only

• The voltage sense pin and the supply pin shall be routed separately to the point wherepower is supplied to the board, so as not to introduce voltage drop on the sense linedue to the current being consumed

• The current shunt has to be soldered directly to the board using 2 3x12mm solder pads

For the 4 channel mux we used a common centroid layout and high precision resistors to builda divider that barely is affected by temperature deviation.

Furthermore the board uses a 4 layer PCB with one Ground and one Power Plane inside soas to reduce EMI.

The top portion of the board features a lot of communication ports. From left to right andtop-down we have connections for LIN (P1 LIN,GND), USB, UART(J11 3.3V-Level GND,RX, TX), serial-programming (J13 MD0, VCC), the connection for the battery disconnectswitch (J15 SW1, GND, SW2), the single supply (J2 VSUP, GND), the battery connector(J1, BAT4, BAT3, BAT3, BAT1, GND) and the dcdc connector (J5 DCDC, VSUP). Thebottom portion features a standard JTAG connector using the pinout described in [1]. Theconnection for the shunt is battery at the top and load at the bottom.

At last we included an LED (D10) to indicate the operation state of the board.

5.4 LiFe Battery Management Firmware

The Software was written in KEIL µVision4 [12] in ANSI-C and debugged using a SEGGERj-link [8] JTAG adapter. The block diagrams (Figure 5.3 & 5.4) give an overview of thesoftware operation.

The flow starts when the battery is attached to the board. The board initializes the twomeasurement systems and tries to load the calibration data from the work flash area of thechip. If that fails, default calibration values are used. After calibration an initial measurementis performed to check if the battery is operating within its SOA (safe operating area). In caseof a success the battery is connected to the load by activating the battery disconnect switchand the board goes on doing continuous measurements. At the end of each measurement itwill detect if any of the individual cells has drifted away from the average cell voltage and in

30


that case activates the balancing feature. The board will keep on measuring for 5 seconds andenter the standby mode if no communication is received. If however the board receives a LINrequest, it will handle this request and reset the timeout timer. So in order to keep the systemin measurement mode regular LIN requests have to be broadcast to the board (which accordsto the LIN Standard). If at any point a measurement is taken which doesn’t comply withthe SOA of the battery, the battery is immediately disconnected using the battery disconnectswitch, and the board enters a reset state in which it will respond to status requests butwon’t allow any other activity. Only a full reset, which can be done via a LIN command orby disconnecting the battery, will bring the system back to normal operation.

The available LIN requests can be seen in the block diagram (Figure 5.4). Lin communicationis handled by an interrupt service routine which evaluates the checksum of the broadcast LINmessage and makes the transported data available to the main program.

Communication to the AS8515 is handled by an interrupt service routine described in Figure5.5 triggered by the new measurement available interrupt of this chip. This ISR will activatethe switches in the mux to measure the individual cell voltages, besides pack voltage andtemperature, and discard each first measurement after the mux is changed in order to isolatethe measurement results from parasitic switching effects.

After being triggered the AS8505/06 chip autonomously handles the whole balancing process.This process is done in three phases:

1. Wait for trigger: In this phase the Chip waits for a trigger signal to begin the balancingprocess:

2. Compare phase: In the compare phase AS8505 detects number of cells connected to thedevice. The connected cell voltages are then compared with upper & lower thresholdsand cell target voltage of all cells connected.

3. Balance phase: The balance phase is basically charging cycle in case of active balancingand discharging cycle in case of passive balancing. The balance phase is divided intoseven time slots. The device will move through all seven time slots irrespective ofnumber of cells connected to the device. One time slot is assigned to each cell (sequentialorder) for charging or discharging. In each timeslot the the CVT NOK flag and theresult of the compare phase is checked for the according cell. If the cell is marked forcharging, the corresponding transmission gates are switched on and a PWM signal issent to the flyback converter. At the end of the current time slot the PWM is turnedoff the switches are disconnected and the device moves to the next timeslot.

This is also explained in Figure 5.6

Functional Safety is provided by:

• Comparison of the individual cell voltage measurements against the pack voltage mea-surement to detect problems with the mux

• Shunt connection breaks are detected by applying a small current from the internalcurrent source

• Measurement of the Interrupt Timing of the AS8515 to determine correct operation

• A hardware watchdog is implemented in the Fujitsu controller to detect softwarehangups

31


Power On

Initial Measurement

LIN timeout?

Wait For measurement_completed

Flag

NO

Maximum Parameter Check

AS8505 CVT_NOK

Standby active?

Everything OK

Wait for AS8510 Interrupt

Go into Standby Mode / Set AS8515 into Standby Mode

MCU Wakeup/AS8515 Setup

YES

YES

InitialisationRead Calibration Values

Activate Power Relais

Maximum Parameter Check

Everything OK

Save Error

Deactivate Power Relais

Parameters not OK

Wait for Host reset

Command received

Execute command

YES

NO

Cell Misbalance Check

Start cell balancing (Trigger AS8505) Misbalance

NO

Stop Balance

Stop cell balancing

No MisbalanceBut AS8505 still active

Figure 5.3: LiFe Management Main Block Diagram

32


LIN

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ell 4

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: C

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4 :

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n0

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: Pri

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Figure 5.4: LiFe Management LIN Block Diagram

33


Figure 5.5: LiFe Management AS8515 Interrupt Block Diagram

34


Figure 5.6: AS8505 state diagram

35

6 PC-Software

The PC Software was developed in C# using Microsoft Visual Studio Express [11] and runson Microsoft Windows XP and upwards. It requires the .NET Framework 4, which canbe downloaded from [10] and the Microchip CDC driver (which is part of the MicrochipApplication Library [22] Subfolder /USB/Device - CDC - Basic Demo/inf) for the USB2LINBoard. The software utilizes the excellent ZedGraph library [17] for all plotting functions. Itwas developed to display data from the battery management board which it requests via LINinterface using the USB2LIN converter board. A Screenshot of the Software can be seen inFigure 6.1

Figure 6.1: PC-Software screenshot

The Software Screen is partitioned in 3 parts.The top part is used for connecting to the USB2LIN interface.The Software will automatically enumerate all USB serial devices and display the associatedCOM port number as well as the Hardware Identifier in the drop down menu at the top of thesoftware, which makes it easy for the user to recognize the correct device without looking itup in the Windows Hardware Manager. The button to the left is to restart the enumerationprocess if new devices have been plugged in since the program start. The buttons to the rightallow connecting and disconnecting the device. A status field will show if the connectionsucceeded.A tab handler provides access to different portions of this software.

As the software was developed for a few different demonstration boards, we will only usethe Life and the calibration tab.The Life tab consists of:

• The button portion

Save: To save all raw data into a .csv file

36

6 PC-Software

Read volt \ current: to make a single read of pack voltage and current

Read cells: to make a single cell voltage reading

Read continuous: to start continuous reading and plotting of all values (updaterate 10Hz)

Pause: to pause the continuous reading

Clear: to clear all display fields

• A Label showing the integrated charge sum in [mAh]

• The left hand side which will display the raw data read back from the Life-BatteryManagement Board.

Values are from left to right

Current[mA]

Voltage[mV]

Charge Integration Sum[µAh]

Impedance [mΩ]

Cell Voltages 1 to 4 [mV]

AS8505 Balance Register

System status byte

Bit 1 Balance is done

Bit 2 Cell voltages are not ok

Bit 3 Balancing active

• The upper graphics will display instantaneous current [mA] and pack voltage [mV]

• The lower graphics will display instantaneous cell voltages [mV] of each individual cell.

• The middle part visualizes the data from the balancing IC. It shows which cells areselected for balancing, and which, if any, are over or under their specified voltage range.

Figure 6.2: PC-Software calibration tab

37

6 PC-Software

The Calib tab shown in Figure 6.2 consists of:

• Input fields for the Cell voltages [V]

• Button Calib Cells: to activate the calibration. Keep in mind that a measurement willbe taken and the raw data compared to the values you input in the fields, and then acalibration set is stored on the microcontroller

• Input fields for the pack voltage [V] Current [A] and Temperature[C]

• Button Calib Base: same as Calib cells but here the calibration for the whole pack andthe temperature is performed

• Button Calib Erase: All calibration data will be erased from the microcontroller

The whole software is available as an installer package, which will not only install the softwarebut also the driver into a specified directory. When Windows asks for a driver for the newdevice, just point it to the install directory driver sub folder.

38

7 Evaluation

7.1 Setup

To evaluate our Battery Management System we created two evaluation platforms:

7.1.1 Car Battery Setup

As a real world application we constructed a 12V car battery replacement consisting of 440Ah LiFePo4 Prismatic cells made by HiPower [6], out battery management electronics anda battery disconnect switch from Tyco electronics [14] encased in a construction of PMMA(acrylic glass). The rendering in Figure 7.1 shows the layout of the 4 individual cells. A plasticintermediate floor seperates the batteries from the electronics. The top has two terminalposts, similar to common lead acid batteries, to make replacement as easy as possible. A LINconnector is accessible from the top via an RJ12 connector.

Figure 7.1: Rendering of the Battery Assembly

The batteries performance data taken from the datasheet are listed in Table 7.1

This battery was integrated in a Citroen C5 shown in Figure 7.2 & 7.3

7.1.2 Lab Setup

Furthermore we used a small 4cell LiFePO4 Battery Pack (Figure7.4) with 4Ah capacityfor lab evaluation and to test the functionality of the battery management as well as thebalancing.

39

7 Evaluation

Nominal Voltage 3.2VMaximum continuous discharge current 120AMaximum peak discharge current 400AMaximum charge current 120AVolumetric energy density 142.7Wh/lGravimetric energy density 95.5Wh/kg

Table 7.1: LiFe Battery Performance Data

Figure 7.2: Citroen C5 with replacement battery installed

40

7 Evaluation

Figure 7.3: Citroen C5 replacement battery closeup

Figure 7.4: 4Cell LiFePo4 Pack from TopFuel

41

7 Evaluation

7.2 Balancing

To evaluate the balancing function, determine its functionality and to estimate what dutycycle would bring the best balance between time efficiency and self heating of the chip we dida couple of lab measurements with the small 4cell LiFePO4 battery.

First we compared internal and external supply for the balancing process. The difference canbe seen in Figures 7.5 & 7.6

Figure 7.5: Balancing with external supply

Figure 7.6: Balancing with internal supply

The reason why the balancing with external source isn’t charging the battery as much aswould be expected lies in the energy consumption of the board. Let us look at an example.We assume that only one of the cells is below the balancing threshold and therefore willget charged by the balancer IC. From that we can calculate that the average current beingcharged into the battery is:

100mA

7cycles= 14, 2mA average charging current

The power consumption of the whole board in active state is roughly 12mA leaving only≈ 2mA as active charging current.

42

7 Evaluation

During testing of the balancing features we also stumbled upon a chip internal latch upbehavior which can be observed in Figure 7.7.

Figure 7.7: Balancing failure

The condition that triggers this behavior is when the current flowing into the lowest mostcell exceeds a value of ≈ 100mA.

Figure 7.8: Schematic of the portion of the AS8505/06 responsible for the problem

With high charging currents from the secondary voltage drop across R1 can be about 0.78Vto 1.5V. As the CGND is connected to ground and TSECL is floating, TSECL can go to-0,78V to -1.5V. This will trigger the ESD protection diode on the TSECL. Current will passthrough the D cond and can trigger the latch-up as the current is in the order of 130mA anda peak current of 300mA.

Two solutions for this problem seem viable:

• Put a 4.3V zener diode between TSECL and TSECH, which limits the over voltage butis wasteful. If the cells are fully discharged, then this may not work

• Decrease the PWM duty cycle to a value where this effect is not triggered.

A comparison of both variants can be seen in Figures 7.9 & 7.10

Judging from these graphs it seems that the added diode consumes a lot of the balancingpower. Therefore it makes more sense to use lower balancing currents than to introduce this

43

7 Evaluation

Figure 7.9: Balancing with Zener Diode

Figure 7.10: Balancing with lower current

44

7 Evaluation

wasteful diode.

7.3 Power Consumption

Power consumption was evaluated for the four operation states the board can enter. Allmeasurements were done using the Agilent 34401A Digital Multimeter.

Measurement + Balancer active: In this state all electrical systems are active. The typicalpower consumption here is ≈ 18mA

Measurement active: In this mode the balancer is in sleep mode whereas the microcontrollerand the AS8515 remain active. Power consumption in this mode is ≈ 10mA

Measurement standby + Balancer woken We run into this mode when the system is in sleepmode but wakes up to perform a balancer check. For this operation the AS8505/06 is wokenvia the WAKE pin and remains active for 1.2sec Power consumption in this mode is ≈ 9mA

Full standby: In this mode the microcontroller enters STOP Mode, the AS8515 is in StandbyMode 1 and the AS8505/06 is also in standby. Current consumption in this mode is ≈ 1mA,which is quite a lot for full standby. The reason for this lies in a few shortcomings of thishardware version as follow:

1. The resistive voltage divider for the reference of AS8505/06 is always connected drawingabout 300µA of current. This will be solved by the next chip sample version which hasan internal disconnect transistor to power down the voltage divider.

2. The AS8515 Standby Mode is not working correctly due to a bug in the recognition ofthe EN pin signal leading to another 300µA of current consumption. This bug is alsoknown and will be corrected in the final chip version.

The total power consumption can be split in the following sections:

Table 7.2: LiFe Management Power Consumption

Device Estimated Power Consumption Measured Power consumptionAS8515 5 5

MB9AF312K 3,9 4AS8505/06 10 9

As can be seen from Table 7.2 the estimated power consumption matches the realized powerconsumption pretty well. A total power consumption of below 20mA is very much acceptablefor a system such as this. The standby power consumption however should be reduced downto ≈ 100µA. An issue that will be resolved by the final version of the respective chip sets.

7.4 Accuracy

Accuracy measurements were done using an Agilent E3631A 80W Triple Output Power Sup-ply, an Agilent 34401A Digital Multimeter and a TTi CPX400A PSU. We tested linearityof all four individual cell voltage measurements as well as common mode dependency of theindividual voltage measurements. In addition we also tested the full voltage and currentchannel for accuracy.

In the first test (shown in Figure 7.11) we sweeped each of the individual cell voltages in 0.1Vincrements and measured all cell voltages. As can be seen the voltage sweep doesn’t influenceany of the other cell voltage readings. Also the measured voltage remains accurate down to0.5V (observable in Figure 7.12) at which point we start making a measurement error, which

45

7 Evaluation

is irrelevant, because the cell voltages won’t ever reach such a level unless they have longpassed their Safe Operating Area.

The second test was to show how well the system performs if the voltages are varying quickly.For this test we ramped the single voltages in 1V increments and observed all the measuredcell voltages. We can observe that the voltage jumps in one cell can lead to a wrong readingin another cell. The reason for this is the way the individual cell voltages are obtained. Weare using a multiplexer to measure the individual tabs of the cell stack. The cell voltagesare obtained by subtracting these values from each other. Because these values can notbe obtained simultaneously (because we are only using one ADC channel) it can happenthat one of the cell values is already updated to the new stack voltage while the other isnot, resulting in a faulty calculation of cell voltage. This can be seen in Figure 7.13. Tocircumvent this one could use multiple synchronous ADCs or a sample and hold circuit foreach voltage. Both solutions are costly, require more board space and are not required in thepractical application since the single cell voltages can’t be properly read during operation ofthe alternator anyway. It is however important that the total pack voltage measurement andthe current measurement are synchronized, so that we may calculate internal resistance ofthe battery pack or use a model to correctly estimate the battery’s SOC.

The last test was to show total pack measurement accuracy for current and voltage. Thistest was performed by stepping the voltage from 5V to 18V in 0.1V increments and thecurrent from 1A to 40A. Measurement accuracy is limited by the accuracy of the suppliesin use, which is 0.05% + 20 mV for the Voltage supply and 0.3% ± 2digit(20mA) for thecurrent source and the remaining output ripple, which is ≤ 350V rms/2mV pp for the voltagesupply. The voltage channel was however corrected by the usage of the Agilent Multimeterwith an accuracy of 0,0020% of the measurement value + 0,0006% of the range value givingan uncertainty of

0.002 ∗ 0.01 ∗ 12 + 0.0006 ∗ 0.01 ∗ 100 = 0.84mV

The conclusion we can draw from these measurements is that the accuracy of the measurementsystem is within the uncertainty of the supply. Overall accuracy can be established to bebetter than 2mV of 0.04% for the full voltage measurement and better than 80mA or 0.5%for the current measurement.

7.5 Safety Shutdown

The autonomous shutdown in case the battery SOA was breached turned out to be toounforgiving to allow normal operation in a car (as can be seen in Figure 7.16). The loadduring ignition triggered the safety shutdown more often than not.In order to allow normaloperation in a car while still being able to safely disconnect the battery in case of an error ashutdown counter was integrated in the battery management. With each measurement cycleif one of the SOA criteria is violated this count is incremented, each cycle if it is not thecase it will be decremented (down to 0). If the counter reaches a critical level, a shutdown isinitiated. The value of the counter was chosen so that the extreme conditions during ignitionwould be tolerated for ≈ 4seconds.

7.6 Car Application

As a final test we put the battery management to use in a real world car application. Asexplained above a Citroen C5 was retrofitted with a LiFePO4 battery pack. This car wasthen started and driven around for a number of times. Figure 7.17 shows one of the test drivecycles we recorded with the software.

We can distinguish a number of load cases in this cycle:

• Standby from 0 to 20 seconds

• Wakeup from 20 to 60 seconds

46

7 Evaluation

Figure 7.11: Common Mode rejection and linearity for the four individual channels

47

7 Evaluation

Figure 7.12: Absolute and relative accuracy for the four individual channels

48

7 Evaluation

Figure 7.13: Common Mode rejection for fast changing voltages

49

7 Evaluation

Figure 7.14: Total Voltage measurement error

50

7 Evaluation

Figure 7.15: Total Current measurement error

51

7 Evaluation

Figure 7.16: Shutdown during ignition of the car

Figure 7.17: Test Car driving cycle

52

7 Evaluation

• Ignition at 60 seconds with current draw of ≈ 350A

• Charging phase where the alternator charges the battery while the diesel engine isrunning. Charge current ≈ 50A till 200 seconds

• Shutdown where current is again drawn from the battery up to 350 seconds

• Subsequent Power down of the various systems

Looking closer at the current and voltage curves we can see that the current has a huge rippleof ≈ 10A, which is also represented in the single cell voltage measurements seen in Figure7.18

Figure 7.18: Test Car driving cycle single cell plot

The reason for this lies in the way a car alternator operates. It is basically a dc excitedsynchronous generator with a regulator that changes the excitation current so that the outputvoltage of the alternator stays at ≈ 14.2V and the output current stays below the maximumrated current for the alternator. The output of the alternator therefore is a 3-phase ACvoltage which is then rectified by a 6 diode network. The battery is then used as a buffer tostabilize the board voltage, leading to the ripple in current flowing to the battery.

53

8 Conclusion

From the measurements performed and discussed in the evaluation section 7 we can concludethat the replacement of existing lead acid batteries with modern LiFePo4 based battery packsis a viable and promising solution for the problems car manufacturers are facing with todaysimplementation. The 4 series connected LiFe cells match very well with the voltage domain ofa classic 12V battery and therefore do not require any changes in the alternator or the boardpower system. The life management and balancing board discussed in this thesis performs allthe necessary functions to safely operate such a new cell stack in any classic car applicationnicely. Therefore it provides a ready-made swap in solution for existing cars as well as a goodtesting platform. With the addition of a full featured battery state of charge and state ofhealth diagnostic algorithm it will also support advanced features like active breaking andmild hybrid support.

54

9 APPENDIX

9.1 USB2LIN Schematic and Layout

9.2 LiFe Battery Management Schematic and Layout

9.3 3D Drawing of the Retrofit Battery

55

9 APPENDIX

11

22

33

44

DD

CC

BB

AA

Title

Num

ber

Rev

isio

nSi

ze A4

Dat

e:05

.04.

2012

Shee

t o

fFi

le:

Z:\T

rans

fer\.

.\usb

2lin

.Sch

Doc

Dra

wn

By:

RA

0/IO

CA

0/D

+/PG

D19

RA

1/IO

CA

1/D

-/PG

C18

RC

1/A

N5/

C12

IN-/I

NT1

/Vre

f-15

RC

2/A

N6/

P1D

/C12

IN2-

/CV

ref/I

NT2

14

RA

4/A

N3/

IOC

A3/

OSC

2/C

LKO

UT

3

VU

SB17

RC

0/A

N4/

C12

IN+/

INT0

/Vre

f+16

RB

5/A

N11

/IOC

B5/

RX

/DT

12

RB

7/IO

CB

7/TX

/CK

10

RC

3/A

N7/

P1C

/C12

IN3-

/PG

M7

RC

4/P1

B/C

12O

UT/

SRQ

6

RC

5/C

CP1

/P1A

/T0C

KI

5

RA

3/IO

CA

3/M

CLR

/VPP

4

VD

D1

RB

4/A

N10

/IOC

B4/

SDI/S

DA

13

RB

6/IO

CB

6/SC

K/S

CL

11

RC

7/A

N9/

SDO

/T1O

SCO

9

RC

6/A

N8/

SS/T

13C

KI/T

1OSC

I8

VSS

20

RA

5/IO

CA

5/O

SC1/

CLK

IN2

U1

PIC

18F1

4K50

GN

D

VC

C

D-

D+

GN

DV

CC

R1

150K

100n

F

C1

C08

05

470n

F

C2

C08

05

D+

D-V

CC

12

Y1

12M

Hz

22pF

C4

C08

0522

pF

C3

C08

05

GN

D

D1

LED

2

D2

LED

2

R2

470R

R3

470R

GN

DR

X

TX

1 2 3

P1 Hea

der 3

GN

D

TXRX

123

P2 Hea

der 3

GN

D

EN1

VSU

P2

LIN

3

VSS

4R

X5

TX6

RES

ET7

VC

C8

U2

AS8

530

RX

TX

VC

C2

POK

4

EN1

GN

D7

FB8

LX5

SWVIN3

SWVOUT6 GN

D_B

9

U3

AS1

340

VSU

P47

0nF

C5

C08

05G

ND

VC

C

GN

D

GN

D

R4

100K

R5

860K

D3

PMEG

4010

BEA

VSU

P

4u7

C6

C12

102u

2

C7

C12

10

GN

D

L1 LPS4

018-

682M

L_

GN

D

S2SW-P

B

VC

C R7

10K

7 62345 1

89J1 U

SB-C

ON

1 2 3 4 5

J3 PicK

it

MC

LR

MC

LR

VC

CG

ND

D+

D-

USB

2 L

IN

R8

1K

Figure 9.1: USB2LIN Schematic

56

9 APPENDIX

PAC102

PAC101COC1

PAC202

PAC201

COC2

PAC302

PAC301

COC3

PAC402

PAC401

COC4

PAC502

PAC501

COC5

PAC602

PAC601

COC6

PAC702

PAC701

COC7

PAD102

PAD101CO

D1PAD2

02PAD2

01COD2

PAD3

02PA

D301CO

D3

PAJ106

PAJ105

PAJ104

PAJ103

PAJ102

PAJ108

PAJ101

PAJ109

PAJ107

PAJ10MH2

PAJ10MH1

COJ1

PAJ301

PAJ302

PAJ303

PAJ304

PAJ305

COJ3

PAL102PAL101

COL1

PAP101

PAP102

PAP103

COP1

PAP201

PAP202

PAP203

COP2

PAR102

PAR101

COR1

PAR202

PAR201 COR2PAR3

02PAR3

01CO

R3

PAR402

PAR401

COR4

PAR502

PAR501

COR5

PAR701

PAR702COR7

PAR802

PAR801

COR8

PAS201

PAS202

COS2

PAU1

011

PAU1

012

PAU1

013

PAU1

014

PAU1

015

PAU1

016

PAU1

017

PAU1

018

PAU1

019

PAU1

020

PAU1010

PAU109

PAU108

PAU107

PAU106

PAU105

PAU104

PAU103

PAU102

PAU101

COU1

PAU2

05

PAU206

PAU2

07

PAU208

PAU2

04

PAU203

PAU2

02

PAU201

COU2

PAU309PA

U308

PAU307

PAU3

06

PAU305

PAU304

PAU3

03

PAU302

PAU3

01CO

U3

PAY102

PAY101

COY1

Figure 9.2: USB2LIN Layout

57

9 APPENDIX

11

22

33

44

DD

CC

BB

AA

Title

Num

ber

Rev

isio

nSi

ze A4

Dat

e:11

.04.

2012

Shee

t o

fFi

le:

Z:\T

rans

fer\.

.\bal

ance

r.Sch

Doc

Dra

wn

By:

FD_O

UT

TSEC

HTS

ECL

TSEC

H

TSEC

L

TRIG_IN_5V

CVT_NOK_5V

BD_OUT_5V

FD_OUTS

CLK

_5V

SD

I_5V

SD

O_5

V

C10 100n

F

C44.7u

F

D5

Q5

C11

D4

GN

D

GN

D

VB

AT

VB

AT

GN

D

5V_8

505

GN

D

GN

D

VSU

P

HR

SHL

HR

SH

H

SD

I

VC

CV

SS

SDO

SCLK

AV

SS

8510/INT

VC

C

8525/CS

RXlin

TXlin

8510/EN

HR

SHL

HRSHH

8510/CS

VSUP

VSS

LIN

VSS

VCC

R2

100R

C1

100n

F

D2

SU

P D

iode

C8

100n

F

R1

100R

D1

DIO

DE

C2

100n

F

C9

100n

F

RSH

L1

VR

EF2

AG

ND

3

AV

DD

4

AV

SS5

ETR

6

ETS

7

VSENSE_GND 9

LIN 10

VSS 11

VSENSE 12

VSUP 13

VCC 15

CSB 16

SCLK

17SD

O18

DV

SS19

DV

DD

20C

HO

P_C

LK21

MEN

22SD

I23

CLK

24

INT26 CST27 TX28 RX29 RESET30 EN31 RSHH32

VSE

NSE

_IN

8

EPAD 33

U2 AS

8515

C7

200n

F

C6

22uF

AV

SS

LIN

12

P1 LIN

SHU

NTH

8510

/CLK

C3

1.2n

F To m

eet G

erm

anO

EM E

MC

requ

irem

ents

8505

/CS_

5V

BA

T1B

AT2

BA

T3B

AT4

BA

T_D

IV_I

N

Q1

BSS

123

Q2

BSS

123

Q3

BSS

123

Q4

BSS

123

BA

T1B

AT2

BA

T3B

AT4

AV

SS

VSS

VB

AT

BA

T_D

IV_I

N

GN

D

VB

AT

GN

D

BAT1

BAT2 BAT1

BAT3 BAT2

BAT4 BAT3

GN

D

D3

SU

P D

iode

J5V

BA

L_SE

LEC

T3V

3

A1

1

VCCA2

A2

3

A3

4

A4

5

A5

6

A6

7

A7

8

A8

9

OE

10

GND 11

B8

12B

713

B6

14B

515

B4

16B

317

B2

18

VCCB19

B1

20

U3

TXS0

108

5V_8

505

3V3

GN

D

R11

100K

R4

91K

0.1

%R

575

K 0

.1%

R6

47K

0.1

%R

724

K 0

.1%

R8

1K 0

.1%

8505

/CS_

5VS

CLK

_5V

SD

I_5V

SD

O_5

V

BD

_OU

T_5V

CV

T_N

OK

_5V

TRIG

_IN

_5V

8505

/CS

SCLK SD

ISD

O

BD

ON

EC

VT_

NO

K85

05/T

RIG

8505

/WA

KE

8505

/OE

SD

OS

DI

SC

LK

8525

/CS

8510

/CS

8510

/CS

8525

/CS

RX

linTX

linTX

linR

Xlin

8510

/EN

8510

/EN

8510

/INT

8510

/INT

S1S2

S3S4

R12

GN

DR13

300K

R14

100K

8505/VREF

8505

/VR

EF

1 2 3 4 5

J1 BA

TT_C

ONB

AT2

BA

T3B

AT4

BA

T1 GN

D

VB

AT

1 2

J2 BA

T_C

ON

_2G

ND

VB

AT

S1 100u

R

SHU

NTL

D6

D7

D8

D9

1 4

10 72 5

11 83 6

12 9

T1 WE-

FLEX

749

1961

11

GN

D

Q7

BSS

123

C5

100n

F

AS8506

TSEC

H1

TSEC

L2

VC

ELL7

3

VC

ELL6

4

VC

ELL5

5

VC

ELL4

6

VC

ELL3

7

VC

ELL2

8

VC

ELL1

9

C_G

ND

10

VREF_IN 12GND 13TRIG_IN 14CLK_IN 15CVT_NOK_OUT 16BD_OUT 17FD_OUT 18WAKE_IN 19

SDO

21SD

I22

SCLK

23C

S24

CEL

L_TH

U25

CEL

L_TH

L26

TEM

P_IN

227

TEM

P_IN

128

V5V

30

V5V_IN31

WAKE_OUT32

FD_IN33

BD_IN34

CVT_NOK_IN35

CLK_OUT36

TRIG_OUT37

VSUP38

MS_SL39

GND_PLATE 41NC 11

NC_T 20

REF

_T29

VREF_H40

U1

8505

/VR

EF_

OU

T

8505

/VR

EF_

OU

T

GN

D

R15

0R

VB

AT

R16

0R

PIC101 PIC102COC1

PIC201 PIC202COC2

PIC301 PIC302

COC3

PIC401

PIC402COC4

PIC501 PIC502COC5

PIC601 PIC602

COC6

PIC701 PIC702

COC7

PIC801

PIC802

COC8

PIC901

PIC902

COC9

PIC100

1

PIC100

2

COC1

0

PIC110

1

PIC110

2COC1

1

PID101

PID102

COD1

PID201PID202

COD2

PID301 PID302

COD3

PID401

PID403

COD4

PID501PID503COD5

PID601PID602CO

D6

PID701PID702CO

D7

PID801PID802CO

D8

PID901PID902CO

D9

PIJ101

PIJ102

PIJ103

PIJ104

PIJ105

COJ1 PI

J201

PIJ202

COJ2

PIJ501

PIJ502

COJ5

PIP101

PIP102

COP1

PIQ101

PIQ102PIQ103 COQ1

PIQ201

PIQ202PIQ203 COQ2

PIQ301

PIQ302PIQ303 COQ3

PIQ401

PIQ402PIQ403 COQ4

PIQ501

PIQ502PIQ503 COQ5

PIQ701

PIQ702PIQ703 COQ7

PIR101

PIR102

COR1

PIR201

PIR202

COR2

PIR401 PIR402COR4

PIR501 PIR502COR5

PIR601 PIR602COR6

PIR701 PIR702

COR7

PIR801 PIR802

COR8

PIR1101 PIR1102COR11


PIR1301 PIR1302

COR1

3

PIR1401 PIR1402

COR1

4

PIR1501 PIR1502

COR15

PIR1601

PIR1602

COR16

PIS101 PIS102PIS103

PIS104

COS1

PIT101

PIT102

PIT103

PIT104

PIT105

PIT106

PIT107

PIT108

PIT109

PIT1010

PIT1011

PIT1012

COT1

PIU101

PIU102

PIU103

PIU104

PIU105

PIU106

PIU107

PIU108

PIU109

PIU1010

PIU1011PIU1012

PIU1013PIU1014

PIU1015PIU1016

PIU1017PIU1018

PIU1019PIU1020

PIU1021

PIU1022

PIU1023

PIU1024

PIU1025

PIU1026

PIU1027

PIU1028

PIU1029

PIU1030

PIU1031PIU1032

PIU1033PIU1034

PIU1035PIU1036

PIU1037PIU1038

PIU1039PIU1040 PIU1041

COU1

PIU201

PIU202

PIU203

PIU204

PIU205

PIU206

PIU207

PIU208

PIU209PIU2010PIU2011PIU2012

PIU2013PIU2015PIU2016

PIU2017

PIU2018

PIU2019

PIU2020

PIU2021

PIU2022

PIU2023

PIU2024

PIU2026PIU2027PIU2028PIU2029PIU2030PIU2031PIU2032

PIU2033

COU2

PIU301

PIU302PIU303

PIU304

PIU305

PIU306

PIU307

PIU308

PIU309

PIU3010

PIU3011

PIU3012

PIU3013

PIU3014

PIU3015

PIU3016

PIU3017

PIU3018

PIU3019PIU3020

COU3

PIC401

PIC501PIU1030

PIU3019PIU301

PIU1024

PIU3020

NL85

050C

S05V

PIR1101PIU3010

PIU307

PIR1302 PIR1401

PIU1012

NL85050VREF

PIR1601

PIU1040

NL85050VREF0OUT

PIQ701

PIU2024

NL85100CLK

PIU2016

NL85

100C

S

PIU2031

NL85

100E

N

PIU2026NL85100INT

PIU2027NL

8525

0CS

PIC102 PIC201

PIC302

PIC402

PIC502

PIC602PIC702

PIC801 PI

C901

PID201

PID601

PIJ105

PIJ202

PIP101

PIQ502

PIQ702

PIR802

PIR1102

PIR1402

PIS102

PIU1010

PIU1013

PIU1027

PIU1028

PIU1039

PIU1041

PIU205

PIU209PIU2011

PIU2019

PIU2033

PIU3011

NLAV

SS

NLVS

S

PID602PID701

PIJ104

PIR701

PIU109

NLBA

T1

PID702PID801

PIJ103

PIR601

PIU108

NLBA

T2

PID802PID901

PIJ102

PIR501

PIU107

NLBA

T3

PIQ102PIQ202

PIQ302PIQ402

PIR801

PIU206

NLBAT0DIV0IN

PIU1017

PIU3012

NLBD0OUT05V

PIU309

PIU308

PIU1016

PIU3013

NLCVT0NOK05V PIQ501

PIU1018

NLFD0OUT

PIC101PIR101

PIU2032NLHRSHH

PIC202PIR201

PIU201

NLHR

SHL

PIC301PIP102

PIU2010 NLLIN

PIC802

PIU202

PIC902

PIU203

PIC100

1

PIJ502

PIR1201

PIT101

PIC100

2 PID503

PIR1202

PID401

PIT107

PID501 PIQ503PIT106

PIQ103PIR402

PIQ203PIR502

PIQ303PIR602

PIQ403PIR702

PIQ703

PIU1019

PIR1301PIR1502PIR1602

PIS101

PIT102

PIT104

PIT103

PIT105

PIT108

PIT1010

PIT109

PIT1011

PIU1011PIU1015

PIU1020

PIU1025

PIU1026

PIU1029

PIU1032PIU1036

PIU1037

PIU207

PIU208

PIU2021

PIU2022

PIU2030

PIU306

PIU3015

PIU2029NL

RXli

n

PIQ401

PIQ301

PIQ201

PIQ101

PIU2017

PIU303

NLSCLK

PIU1023

PIU3018

NLSC

LK05

V

PIU2023

PIU304

NLSDI

PIU1022

PIU3017

NLSD

I05V

PIU2018

PIU305

NLSD

O

PIU1021

PIU3016

NLSD

O05V

PIR102

PIS103

NLSHUNTH

PIR202

PIS104

NLSHUNTL

PIU1014

PIU3014

NLTRIG0IN05V

PIC110

1

PID302

PID403

PIU101

NLTS

ECH

PIC110

2

PID301

PIT1012

PIU102

NLTS

ECL

PIU2028NL

TXli

n

PID101

PID202

PID902

PIJ101

PIJ201

PIJ501

PIR401

PIR1501

PIU103

PIU104

PIU105

PIU106

PIU1031PIU1033

PIU1034PIU1035

PIU1038

PIU2012

NLBA

T4

PIU204

PIU2015

PIU2020

PIU302NLVCC

PIC601PIC701

PID102

PIU2013 NLVSUP

Figure 9.3: LiFe Management Schematic Page 1

58

9 APPENDIX

11

22

33

44

DD

CC

BB

AA

Title

Num

ber

Rev

isio

nSi

ze A4

Dat

e:11

.04.

2012

Shee

t o

fFi

le:

Z:\T

rans

fer\.

.\mcu

.Sch

Doc

Dra

wn

By:

VC

C1

P50/

INT0

0_0/

AIN

0_2/

SIN

3_1

2

P51/

INT0

1_0/

BIN

0_2/

SOT3

_13

P52/

INT0

2_0/

ZIN

0_2/

SCK

3_1

4

P39/

DTT

I0X

_0/A

DTG

_25

P3A

/RTO

00_0

/TIO

A0_

1/R

TCC

O_2

/SU

BO

UT_

26

P3B

/RTO

01_0

/TIO

A1_

17

P3C

/RTO

02_0

/TIO

A2_

18

P3D

/RTO

03_0

/TIO

A3_

19

P3E/

RTO

04_0

/TIO

A4_

110

P3F/

RTO

05_0

/TIO

A5_

111

VSS

12

C13

VC

C14

P46/

X0A

15

P47/

X1A

16

INIT

X17

P49/

TIO

B0_

018

P4A

/TIO

B1_

019

PE0/

MD

120

MD

021

PE2/

X0

22

PE3/

X1

23

VSS

24P1

0/A

N00

25P1

1/A

N01

/SIN

1_1/

INT0

2_1/

FRC

K0_

2/IC

02_0

/WK

UP1

26P1

2/A

N02

/SO

T1_1

/IC00

_227

P13/

AN

03/S

CK

1_1/

IC01

_2/R

TCC

O_1

/SU

BO

UT_

128

P14/

AN

04/S

IN0_

1/IN

T03_

1/IC

02_2

29P1

5/A

N05

/SO

T0_1

/IC03

_230

AV

CC

31A

VR

H32

AV

SS33

P23/

AN

06/S

CK

0_0/

TIO

A7_

134

P22/

AN

07/S

OT0

_0/T

IOB

7_1

35P2

1/SI

N0_

0/IN

T06_

1/W

KU

P236

P00/

TRST

X37

P01/

TCK

/SW

CLK

38P0

2/TD

I39

P03/

TMS/

SWD

IO40

P04/

TDO

/SW

O41

P0F/

NM

IX/C

RO

UT_

1/R

TCC

O_0

/SU

BO

UT_

0/W

KU

P042

P61/

SOT5

_0/T

IOB

2_2/

UH

CO

NX

/DTT

I0X

_243

P60/

SIN

5_0/

TIO

A2_

2/IN

T15_

1/IC

00_0

/WK

UP3

44U

SBV

CC

45P8

0/U

DM

046

P81/

UD

P047

VSS

48U

4

MB

9AF3

12K

GN

D

GN

D3V

3

GN

D

3V3

GN

D

C20

4u7

6V

GN

D3V3

C

C

11

22

33

44

55

66

77

88

99

1010

1111

1212

1313

1414

1515

1616

1717

1818

1919

2020

J12

JTA

GG

ND

nTRST

TDI

TMS

TCK

RTC

KTD

ORES

ETDBGRQ

JTAG_5V

TDO

TDI

nTRST

TMS

TCK

RES

ET

X0 X1

D-

D+

GN

D

7 62345 1

89J1

0

USB

-CO

N

D+

D-

SIN0

SIN1

SOT0

SOT1

SCK1

TXlin

RX

lin

SCLK

SDO

SDI

8510

/CS

8525

/CS

8510

/EN

GN

D

8505

/OE

BD

ON

E

CV

T_N

OK

8505

/TR

IG

8505

/CS

8505

/WA

KE

8510

/INT

12

Y1

4MH

z

C23

12pF

C24

12pF

GN

D

X0 X1

MD0

R20

27R

R21

27R

Q10

BC

857B

R22

1K5

R23

2K2

R24

10K

3V3

3V3

UHCONX

3V3

UHCONX

S1S2S3S4

J13

PRO

G_J

MP

MD0

R25

1K R26

10K

GN

D

3V3

1 2 3

J11

UA

RT0

SOT0

SIN0 GN

D

P_SW_1

P_SW_2

3V3 R

2710

K

RES

ET

LED

GN

D

D10

LED

LED

R28

470R

USB_VCC

Q11

IRFM

L824

4TR

PBF

Q12

IRFM

L824

4TR

PBF

GN

D

P_SW_1

P_SW_2

123J1

5B

ATT

_SW

ITC

H

VB

AT

3V3

R29

20K

R30

10K

GN

D

INT15_1

INT15_1

C21

100nF

C22

100nF

USB_D+

USB_D-

I/O 1

1

GN

D2

I/O 2

3I/O

24

VB

US

5

I/O 1

6U

5

USB

LC6-

2

3V3

PIC2001 PIC2002CO

C20

PIC2101 PIC2102CO

C21

PIC2201 PIC2202CO

C22

PIC2301 PIC2302COC23

PIC2401 PIC2402COC24

PID1001 PID1002

COD10

PIJ1

001

PIJ1

002

PIJ1

003

PIJ1

004

PIJ1005

PIJ1

006

PIJ1

007

PIJ1

008

PIJ1009COJ

10

PIJ1101

PIJ1102

PIJ1103

COJ11

PIJ1201

PIJ1202

PIJ1203

PIJ1204

PIJ1205

PIJ1206

PIJ1207

PIJ1208

PIJ1209

PIJ12010

PIJ12011

PIJ12012

PIJ12013

PIJ12014

PIJ12015

PIJ12016

PIJ12017

PIJ12018

PIJ12019

PIJ12020

COJ12

PIJ1301

PIJ1302

COJ13

PIJ1501PIJ1502

PIJ1503COJ15

PIQ1001

PIQ1002 PIQ1003

COQ10

PIQ1101

PIQ1102PIQ1103COQ11

PIQ1201

PIQ1202PIQ1203COQ12

PIR2001

PIR2002

COR2

0

PIR210

1PIR

2102

COR2

1

PIR2201 PIR2202

COR2

2

PIR2301

PIR2302

COR23

PIR2401PIR2402CO

R24

PIR2501 PIR2502

COR2

5

PIR2601 PIR2602

COR2

6



PIR2901

PIR2902COR29

PIR3001PIR3002COR

30

PIU401

PIU402

PIU403

PIU404

PIU405

PIU406

PIU407

PIU408

PIU409

PIU4010

PIU4011

PIU4012

PIU4013

PIU4014

PIU4015

PIU4016

PIU4017

PIU4018

PIU4019

PIU4020

PIU4021

PIU4022

PIU4023

PIU4024

PIU4025

PIU4026

PIU4027

PIU4028

PIU4029

PIU4030

PIU4031

PIU4032

PIU4033

PIU4034

PIU4035

PIU4036

PIU4037

PIU4038

PIU4039

PIU4040

PIU4041

PIU4042

PIU4043

PIU4044

PIU4045

PIU4046

PIU4047

PIU4048

COU4

PIU501

PIU502

PIU503

PIU504

PIU505

PIU506

COU5

PIY101PIY102 COY1

PIC2101PIC2201

PIJ1201

PIQ1002PIR2402

PIR2501

PIR2701

PIU401

PIU4014

PIU4031

PIU4045

PIU4018

PIU409

PIU4016

PIU4019

PIU4011

PIU405

PIU404

PIU406

PIU4010

PIC2001

PIU4013

NLC

PIU4015

PIR2002

PIR2202

PIU4047

NLD0

PIR210

2

PIU4046

NLD0

PIJ12017

NLDBGRQ

PIC2002PIC2102

PIC2202

PIC2302 PIC2401

PIJ1

004

PIJ1005

PIJ1

006

PIJ1

007

PIJ1

008

PIJ1009

PIJ1103

PIJ1204

PIJ1206

PIJ1208

PIJ12010

PIJ12012

PIJ12014

PIJ12016

PIJ12018

PIJ12020

PIQ1102PIQ1202

PIR2602

PIR2802

PIR3001

PIU4012

PIU4020

PIU4024

PIU4033

PIU4048

PIU502

PIR2901

PIU4044

NLIN

T150

1

PIJ12019

NLJTAG05V

PID1001

PIU407

NLLE

D

PIJ1302 PIR2601

PIU4021

NLMD0

PID1002 PIR2801

PIJ1

001

PIR2902

PIR3002

PIU505

PIJ1202

PIJ1301PIR2502

PIJ1501

PIQ1203

PIJ1503

PIQ1103

PIQ1001

PIR2301

PIQ1003 PIR2201

PIR2001

PIU506

PIR210

1PIU504

PIU4032

PIJ1203

PIU4037

NLnT

RST

PIQ1101

PIU408

NLP0SW01

PIQ1201

PIU4042

NLP0SW02

PIJ12015

PIR2702

PIU4017

NLRESET

PIJ12011

NLRT

CK

PIU402

PIU4025

PIU4029

PIU4030

PIU4034

PIU4028

NLSC

K1

PIJ1102

PIU4036

NLSI

N0

PIU4026

NLSI

N1

PIJ1101

PIU4035

NLSO

T0

PIU4027

NLSO

T1

PIJ1209

PIU4038

NLTCK

PIJ1205

PIU4039

NLTD

I

PIJ12013

PIU4041

NLTDO

PIJ1207

PIU4040

NLTMS

PIU403

PIR2302

PIR2401

PIU4043

NLUHCONX

PIJ1

003

PIU501

NLUSB0D0

PIJ1

002

PIU503

NLUS

B0D0

NLUSB0VCC

PIJ1502PIC2301

PIU4022

PIY102NL

X0

PIC2402

PIU4023

PIY101NL

X1

Figure 9.4: LiFe Management Schematic Page 2

59

9 APPENDIX

PAC102

PAC101 COC1

PAC202

PAC201

COC2

PAC302

PAC301

COC3

PAC402

PAC401

COC4

PAC502

PAC501

COC5

PAC602

PAC601

COC6

PAC702

PAC701

COC7

PAC802

PAC801COC8 PAC90

2PAC9

01COC9

PAC100

2

PAC100

1CO

C10

PAC1102

PAC1101 COC1

1

PAC200

2PAC

2001

COC20PAC2

102

PAC2101

COC21

PAC2202

PAC2201

COC2

2

PAC2302PA

C2301COC23

PAC2402PAC

2401COC24

PAD1

01PA

D102

COD1

PAD202

PAD201 COD2

PAD302P

AD301

COD3

PAD401PAD402

PAD403COD4

PAD5

01

PAD5

02PA

D503COD5

PAD602

PAD601COD6

PAD702

PAD701COD7

PAD802

PAD801COD8

PAD902

PAD901COD9

PAD1001

PAD1002

COD1

0

PAJ105

PAJ104

PAJ103

PAJ102

PAJ101

COJ1

PAJ202

PAJ201

COJ2

PAJ502

PAJ501

COJ5

PAJ1007

PAJ1009

PAJ1001PAJ10

08PAJ1002PAJ1003PAJ1004PAJ1005

PAJ1006PAJ100

MH1PAJ100

MH2

COJ10

PAJ1103

PAJ1102

PAJ1101

COJ1

1

PAJ12020

PAJ12019

PAJ12018

PAJ12017

PAJ12016

PAJ12015

PAJ12014

PAJ12013

PAJ12012

PAJ12011

PAJ12010

PAJ1209

PAJ1208

PAJ1207

PAJ1206

PAJ1205

PAJ1204

PAJ1203

PAJ1202

PAJ1201

COJ1

2

PAJ1302

PAJ1301

COJ1

3

PAJ1501

PAJ1502

PAJ1503

COJ1

5PAP

101

PAP102

COP1

PAQ103

PAQ102

PAQ101

COQ1

PAQ203

PAQ202

PAQ201

COQ2

PAQ303

PAQ302

PAQ301

COQ3

PAQ403

PAQ402

PAQ401

COQ4

PAQ503

PAQ502

PAQ501

COQ5

PAQ703

PAQ702

PAQ701

COQ7

PAQ1001PAQ1002

PAQ1003

COQ10

PAQ1101

PAQ1102

PAQ1103

COQ1

1

PAQ1201

PAQ1202

PAQ1203

COQ1

2

PAR102

PAR101 COR1PAR2

02PAR20

1COR2

PAR402

PAR401

COR4

PAR502

PAR501

COR5

PAR602

PAR601

COR6

PAR702

PAR701

COR7

PAR802

PAR801

COR8

PAR1102

PAR1101COR11

PAR120

2

PAR1201

COR1

2

PAR1302

PAR1301

COR1

3

PAR1402

PAR1401

COR1

4

PAR1501

PAR1502

COR1

5

PAR160

2

PAR160

1CO

R16

PAR200

2

PAR200

1COR20

PAR210

2

PAR210

1

COR21

PAR2202

PAR2201

COR22

PAR230

2

PAR230

1

COR23

PAR240

2

PAR240

1

COR24

PAR250

2

PAR250

1

COR25

PAR260

2

PAR260

1

COR2

6

PAR2702

PAR2701

COR27

PAR280

2

PAR280

1COR28

PAR290

2

PAR290

1

COR29

PAR300

2

PAR300

1

COR30

PAS104

PAS103

PAS102

PAS101

COS1

PAT107

PAT108

PAT109

PAT101

0PAT

1011

PAT101

2

PAT106

PAT105

PAT104

PAT103

PAT102

PAT101

COT1

PAU1041

PAU1040PAU1039PAU

1038PAU1037PAU1036

PAU1035PAU1034PAU

1033PAU1032PAU1031

PAU1030

PAU102

9PAU1028

PAU1027

PAU1026

PAU1025

PAU1024

PAU102

3PAU1022

PAU1021

PAU1020PAU1019PAU1018PAU1017PAU1016PAU1015PAU1014PAU1013

PAU1012PAU1011PAU1010

PAU109

PAU108

PAU107

PAU106

PAU105

PAU104

PAU103

PAU102

PAU101

COU1

PAU201

PAU202

PAU203

PAU204

PAU205

PAU206

PAU207

PAU208

PAU209PAU2010

PAU2011PAU2012

PAU2013PAU2014

PAU2015PAU2016

PAU2017

PAU2018

PAU2019

PAU2020

PAU2021

PAU2022

PAU2023

PAU2024

PAU2025PAU2026

PAU2027PAU2028

PAU2029PAU2030

PAU2031PAU2032 PAU2

033COU2

PAU301PAU302PAU303PA

U304PAU305PAU306PAU3

07PAU308PAU309PAU301

0

PAU3020PAU3019PAU3018P

AU3017PAU3016PAU3015

PAU3014PAU3013PAU3012P

AU3011COU3

PAU4048PAU4047PAU4046PAU4045PAU

4044PAU4043PAU4042PAU4041PAU404

0PAU4039PAU4038PAU4037 P

AU4036

PAU4035

PAU4

034

PAU4

033

PAU4032

PAU4031

PAU4030

PAU4029

PAU4

028

PAU4027

PAU4026

PAU4025

PAU4024PAU4023PAU4022PAU4021PAU4020PAU4019PAU4018PAU4017PAU4016PAU4015PAU4014PAU4013PAU4012

PAU4011

PAU4010

PAU409

PAU408

PAU407

PAU406

PAU405

PAU404

PAU403

PAU402

PAU401

COU4

PAU506PAU

505PAU504PAU50

3PAU5

02PAU50

1

COU5

PAY1

02PA

Y101

COY1

PAC401

PAC501

PAU1030

PAU3019 PAU301

PAU4018

PAU1024

PAU3020

PAR1101

PAU3010

PAU409

PAU307

PAU4016PAR1

302

PAR1401

PAU1012

PAR160

1

PAU1040

PAQ701

PAU4019

PAU2024

PAU2016PAU4011

PAU2031

PAU405

PAU2026PAU404

PAU2027

PAU406

PAC102PAC201

PAC302

PAC402

PAC502

PAC602

PAC702

PAC801

PAC901

PAC200

2

PAC2102PAC2202

PAC2302

PAC2401

PAD201

PAD601

PAJ105

PAJ202

PAJ1004PAJ1005PAJ10

06

PAJ1007

PAJ1008

PAJ1009

PAJ1103

PAJ1204

PAJ1206

PAJ1208

PAJ12010

PAJ12012

PAJ12014

PAJ12016

PAJ12018

PAJ12020

PAP101

PAQ502

PAQ702

PAQ1102

PAQ1202

PAR802

PAR1102

PAR1402

PAR260

2

PAR280

2

PAR300

1

PAS102

PAU1010

PAU1013

PAU1027

PAU1028

PAU1039 PAU1041

PAU205

PAU209PAU2011

PAU2019

PAU2033

PAU3011

PAU4012

PAU4020PAU4024PA

U403

3

PAU4048PAU502

PAD602

PAD701

PAJ104

PAR701

PAU109

PAD702

PAD801

PAJ103

PAR601

PAU108

PAD802

PAD901

PAJ102

PAR501

PAU107

PAD1

01PAD2

02

PAD902

PAJ101

PAJ201

PAJ501

PAJ1502

PAR401

PAR1501

PAU103

PAU104

PAU105

PAU106

PAU1031PAU1033

PAU1034PAU1035PAU1038

PAU2012

PAQ102

PAQ202

PAQ302

PAQ402

PAR801

PAU206

PAU1017

PAU3012 PAU309

PAU4010

PAC200

1PAU4013

PAU308

PAU4015PAU1016

PAU3013

PAR200

2

PAR2202

PAU4047PAR210

2

PAU4046

PAJ12017

PAQ501

PAU1018

PAC101

PAR101

PAU2032

PAC202

PAR201

PAU201

PAR290

1

PAU4044

PAJ12019

PAD1001

PAU407

PAC301

PAP102

PAU2010

PAJ1302

PAR260

1

PAU4021

PAC802

PAU202

PAC902

PAU203

PAC100

1 PAJ502PAR1

201

PAT101

PAC100

2PAD5

03

PAR120

2

PAD401PAT

107PA

D501

PAQ503

PAT106

PAD1002

PAR280

1

PAJ1001PAR

2902

PAR300

2

PAU505

PAJ1301

PAR250

2

PAJ1501

PAQ1203

PAJ1503

PAQ1103

PAQ103

PAR402

PAQ203

PAR502

PAQ303

PAR602

PAQ403

PAR702

PAQ703

PAU1019

PAQ1001PAR230

1PAQ1003PAR22

01

PAR1301

PAR1502

PAR160

2

PAR200

1

PAU506

PAR210

1

PAU504

PAT102

PAT104

PAT103

PAT105

PAT108

PAT101

0PAT

109

PAT101

1

PAJ1203

PAU4037

PAQ1101

PAU408

PAQ1201

PAU4042

PAJ12015PAR27

02

PAU4017

PAJ12011

PAU2029PAU402

PAQ401

PAU4025

PAQ301

PAU4029

PAQ201

PAU4030

PAQ101

PAU4

034

PAU2017

PAU303

PAU4

028

PAU102

3

PAU3018

PAU2023

PAU304

PAU4027

PAU1022

PAU3017

PAU2018

PAU305

PAU4026

PAU1021

PAU3016

PAR102

PAS103

PAR202

PAS104

PAJ1102

PAU4036PAJ1

101

PAU4035

PAJ1209

PAU4038

PAJ1205

PAU4039 PAJ12013

PAU4041

PAJ1207

PAU4040

PAU1014

PAU3014

PAC1101PAD302PAD403

PAU101

PAC1102

PAD301

PAT101

2

PAU102

PAU2028PAU403

PAR230

2PAR

2401

PAU4043

PAJ1003PAU50

1

PAJ1002PAU503

PAC2101

PAC2201

PAJ1201

PAQ1002PAR240

2

PAR250

1

PAR2701

PAU204

PAU2015

PAU2020

PAU302

PAU401

PAU4014

PAU4031

PAU4045

PAC601

PAC701

PAD1

02

PAU2013

PAC2301

PAU4022

PAY1

02

PAC2402

PAU4023 PAY1

01

Figure 9.5: LiFe Management Layout

60

9 APPENDIX

212

274

134

battery_packGEWICHT:

A4

BLATT 1 VON 1MASSSTAB:1:2

ZEICHNUNGSNR.

BENENNUNG:

ÄNDERUNGZEICHNUNG NICHT SKALIEREN

WERKSTOFF:

DATUMSIGNATURNAME

ENTGRATENUND SCHARFEKANTENBRECHEN

OBERFLÄCHENGÜTE:WENN NICHT ANDERS DEFINIERT:BEMASSUNGEN SIND IN MILLIMETEROBERFLÄCHENBESCHAFFENHEIT:TOLERANZEN: LINEAR: WINKEL:

QUALITÄT

PRODUKTION

GENEHMIGT

GEPRÜFT

GEZEICHNET

Figure 9.6: Long side board

61

List of Figures

1.1 Typical car battery system . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.2 Diagram of the 4 lead-acid battery charging phases [24] . . . . . . . . . . . . 91.3 Influence of the discharge current on the usable capacity [5] . . . . . . . . . . 101.4 Influence of the discharge current on the usable capacity [4] . . . . . . . . . . 101.5 Influence of the discharge current on the cycle life [5] . . . . . . . . . . . . . . 11

2.1 Comparison of energy density of various battery types [20] . . . . . . . . . . . 132.2 Comparison of discharge curves of various battery types [7] . . . . . . . . . . 132.3 Plot of charging operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.4 Plot of discharging operation at various discharge rates . . . . . . . . . . . . . 162.5 Plot of discharging operation at various temperatures . . . . . . . . . . . . . 162.6 Block diagram of the AS8505/06 chip including peripheral components . . . . 17

3.1 Typical LIN network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.2 LIN Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193.3 LIN Break field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193.4 LIN Sync field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203.5 LIN PID field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203.6 LIN Master Task [21]p.41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.7 LIN Slave Task [21]p.43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4.1 USB2LIN Software Flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . 244.2 HID Bootlader after successful flashing operation . . . . . . . . . . . . . . . . 25

5.1 Battery Management Hardware Block Diagram . . . . . . . . . . . . . . . . . 285.2 Secondary current of the flyback transformer . . . . . . . . . . . . . . . . . . 295.3 LiFe Management Main Block Diagram . . . . . . . . . . . . . . . . . . . . . 325.4 LiFe Management LIN Block Diagram . . . . . . . . . . . . . . . . . . . . . . 335.5 LiFe Management AS8515 Interrupt Block Diagram . . . . . . . . . . . . . . 345.6 AS8505 state diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

6.1 PC-Software screenshot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366.2 PC-Software calibration tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

7.1 Rendering of the Battery Assembly . . . . . . . . . . . . . . . . . . . . . . . . 397.2 Citroen C5 with replacement battery installed . . . . . . . . . . . . . . . . . . 407.3 Citroen C5 replacement battery closeup . . . . . . . . . . . . . . . . . . . . . 417.4 4Cell LiFePo4 Pack from TopFuel . . . . . . . . . . . . . . . . . . . . . . . . . 417.5 Balancing with external supply . . . . . . . . . . . . . . . . . . . . . . . . . . 427.6 Balancing with internal supply . . . . . . . . . . . . . . . . . . . . . . . . . . 427.7 Balancing failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437.8 Schematic of the portion of the AS8505/06 responsible for the problem . . . . 437.9 Balancing with Zener Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447.10 Balancing with lower current . . . . . . . . . . . . . . . . . . . . . . . . . . . 447.11 Common Mode rejection and linearity for the four individual channels . . . . 477.12 Absolute and relative accuracy for the four individual channels . . . . . . . . 487.13 Common Mode rejection for fast changing voltages . . . . . . . . . . . . . . . 497.14 Total Voltage measurement error . . . . . . . . . . . . . . . . . . . . . . . . . 507.15 Total Current measurement error . . . . . . . . . . . . . . . . . . . . . . . . . 517.16 Shutdown during ignition of the car . . . . . . . . . . . . . . . . . . . . . . . 527.17 Test Car driving cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

62

List of Figures

7.18 Test Car driving cycle single cell plot . . . . . . . . . . . . . . . . . . . . . . . 53

9.1 USB2LIN Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569.2 USB2LIN Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579.3 LiFe Management Schematic Page 1 . . . . . . . . . . . . . . . . . . . . . . . 589.4 LiFe Management Schematic Page 2 . . . . . . . . . . . . . . . . . . . . . . . 599.5 LiFe Management Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609.6 Long side board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

63

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65

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Documents

Feasibility study of Li-Fe battery packs for a 12v car system