Testing of Station Batteries

8/16/2019 Testing of Station Batteries

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Testing of Stationary

BatteriesA PRESENTATION BY : 13BEE096, 13BEE097 AND 13BEE098


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Introduction

Conventional battery test methods measure the stored energy through afull discharge.

There is a move towards methods that take only seconds instead of hours

Public safety, medical and defense organizations still depend on testinvolving periodic full discharge/charge cycles.


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Reasons And Types of Tests

Periodic testing and maintenance of battery banks is imperative to ensurereliable delivery of power when they are called upon.

There are a number of different tests like: visual inspections, capacity testimpedance test, float voltage and current measurements, discharge test

individual cell condition, inter-cell resistance etc. We will be going todiscuss three of above.

The discharge test (also known as load test or capacity test) is the only testhat can accurately measure the true capacity of a battery system and inturn determine the state of health of batteries.


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Capacity Test : Introduction

A controlled constant-current or constant-power discharge of a battery toa specified terminal voltage.

This test is preformed regularly for tracking the battery’s health and actuacapacity and estimating remaining life of the battery. When the battery inew its capacity might be slightly lower than specified.

During the test it is measured how much capacity (current x timeexpressed in Ah) the battery can deliver before the terminal voltagedrops to the end of discharge voltage times the number of cells.


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Capacity Test : Observation

It is recommended to select a test time that is approximately the same athe battery’s duty cycle. Common test times are 5 or 8 hours andcommon end of discharge voltage for a lead acid cell is 1.75 or 1.80 V.

It is recommended to use the same testing time during the battery’lifetime. This will improve accuracy when trending how battery’s capacitychanges.


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Capacity Test : Conclusions


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Impedance test : Introduction

Its an internal ohmic test, generally performed to indicate conditions obattery.

Since it tests the condition of the entire electrical path of a battery fromterminal plate to terminal plate, impedance can find weaknesses in celland intercell connectors easily and reliably.


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Impedance test : Observation

Determined by applying an AC current signal, measuring the AC voltagedrop across the cell or inter cell connector and calculating theimpedance using Ohm’s Law. In practice, not only is the AC voltage dropmeasured but so is the AC current.


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Impedance test : Conclusion


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Float Current Testing : Introduction

There are two types of DC current on a battery: recharge current which ithe current applied to recharge a battery after a discharge and floacurrent which is the current used to maintain a battery in a fully chargedstate.

When there is a large voltage difference such as after a discharge thecurrent is high and is limited by the charger until the voltage differencebecomes less. When the current is on the plateau in the graph below, thiis called current limit. When the voltage differential becomes less, thecharge current is reduced as depicted on the downward sloping chargecurrent line on the graph shown in figure


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Float Current Testing : Observation


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Float Current Testing : Conclusion

Float current can increase for a couple of reasons as ground faults onfloating battery systems and internal battery faults.

As a battery’s internal impedance increases, it takes more current to pasthrough that higher impedance. The increase in float current can be anindicator of battery faults.

Float current is main cause of Thermal Runaway, Some of the causes thacan lead to thermal runaway are shorted cells, ground faults, dry-outexcessive charging and insufficient heat removal.

By measuring float current, it may be possible to avoid catastrophic failureof the battery and damage to connected and nearby equipment.


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Other Tests:

Acceptance Test : A constant-current or constant-power capacity tesmade on a new battery to determine if it meets specifications omanufacturer’s ratings.

Critical period test: Analyzing portion of the duty cycle that is the mos

severe, or the specified time period of the battery duty cycle that is mossevere.

Modified performance test: A test of battery capacity and the ability othe battery to satisfy the duty cycle.


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Other tests

Service test: A test of a battery’s capability, to satisfy the battery dutycycle.

Performance test: A constant-current or constant-power capacity testmade on a battery after it has been in service, to detect any change in

the capacity.


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References

https://standards.ieee.org/findstds/redline_ex.pdf

http://powerpoint.ie/battery-impedance-testing/

http://www.battcon.com/PapersFinal2014/6%20Chhajer%20Paper%202014%20Final.pdf

Today’s Sarcasm : Thanks for Watching
https://standards.ieee.org/findstds/redline_ex.pdfhttps://standards.ieee.org/findstds/redline_ex.pdfhttps://standards.ieee.org/findstds/redline_ex.pdfhttp://powerpoint.ie/battery-impedance-testing/http://powerpoint.ie/battery-impedance-testing/http://www.battcon.com/PapersFinal2014/6%20Chhajer%20Paper%202014%20Final.pdfhttp://www.battcon.com/PapersFinal2014/6%20Chhajer%20Paper%202014%20Final.pdfhttp://www.battcon.com/PapersFinal2014/6%20Chhajer%20Paper%202014%20Final.pdfhttp://www.battcon.com/PapersFinal2014/6%20Chhajer%20Paper%202014%20Final.pdfhttp://www.battcon.com/PapersFinal2014/6%20Chhajer%20Paper%202014%20Final.pdfhttp://powerpoint.ie/battery-impedance-testing/https://standards.ieee.org/findstds/redline_ex.pdf

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Testing of Station Batteries