Download pdf - Battery Ah Sizing Claculation

BATTERY SIZING CALCULATION

Design SMF battery bank required to supply a system having MD = 160kVA and

pf of 0.8 for 30 minutes

Constant Power Discharge

1000

( ) .

kVA pfDischarge rating in Watts per battery

Efficiency No of batteries

CASE -1

Considering 40 no. of batteries

1000

.

160 1000 0.8 3404.25

0.94 40

kVA pfDischarge rating per battery

No of batteries

W

10 % 25%

3404.25 1.1 1.25 4680.85

Considering Design Margin and Ageing Factor

Discharge rating in Watts per block W

Considering End Cell voltage of 1.7V/C, the following table gives Discharge in

W/block.

Melvin Koshy Indian Space Research Organisation [email protected]

From the table, for 15min, A412/180A (Sonnenschein make) gives 2976W/block.

Hence our understanding is that we can use two such blocks to achieve the

required backup time.

Check

.

2976 2 15 = 19.07 .

4680.85

Specified discharge rating in Watts No of banks Specified backup timeBackup time achieved

Required discharge rating in Watts

min

Thus, if we use two banks of A412/180A with 40 batteries each, a backup time

of only 19.07 min. is achieved.

2

1

3

4

5

10 11

20

Double Row Double Tier

Tier 1 = 20 batteries


ARRANGEMENT OF BATTERIES IN BATTERY ROOM

OVERALL TOTAL = 40 batteries

CASE -2

Since, a backup time of only 19.07 min. is achieved in the previous case; weve to

consider more number of cells inorder to get the desired backup time of 30 min.

Considering 80 no. of cells

1000

.

160 1000 0.8 1.1 1.25 2340.42

0.94 80

kVA pfDischarge rating per battery Design Margin Ageing Factor

No of cells

W

From, the table, for an End Cell voltage of 1.7V/C, the Discharge in W/block for

15min with A412/180A batteries is 2976W/block.

If two such blocks (banks) are employed, the backup time achieved is

2976 2 15 38.14 .

2340.42Backup time achieved min

Hence two banks of A412/180A with 80 batteries each a backup time of

38.14 min. is achieved. This is acceptable

2

1

3

4

5

10 11

20

BANK - 1




TOTAL = 40 batteries


2

1

3

4

5

10 11

20

BANK - 2






Constant Current Discharge

1000

.

kVA pfDischarge rating in Amps per battery

Min DC Voltage Efficiency

Consider an End Cell Voltage of 1.7 V/cell, then if 40 nos. of batteries are

considered,

. 1.7 6 10.2 6

. 10.2 40 408

dc

dc

Min V per cell V A battery comprises cells

Min V of entire bank V

160 1000 0.8 333.75

408 0.94

&

333.75 1.1 1.25 458.91

Discharge rating per battery A

Considering Design Margin Ageing Factor


The following table gives Discharge in A/block for End Cell Voltage of 1.7V/C

From the table, for 15min, A412/180A gives 234A/block. Hence if two such

blocks (banks) are employed, the backup time achieved is

.

234 2 15 15.3 .

458.91

Specified discharge rating No of banks Specified backup timeBackup time achieved

Required discharge rating

min

Thus, if we use two banks of A412/180A with 40 batteries each, a backup time

of only 15.3 min. is achieved.

2

1

3

4

5

10 11

20






CASE -2

Since, a backup time of only 15.3 min. is achieved in the previous case; weve to

consider more number of cells inorder to get the desired backup time of 30 min.

Considering 80 no. of cells with End Cell Voltage of 1.70V/C

. 10.2 840 408

160 1000 0.8 166.87

816 0.94

&

166.87 1.1 1.25 229.45

dcMin V of entire bank V


Considering Design Margin Ageing Factor


From the table, for 15min, A412/180A gives 234A/block. Hence if two such

blocks (banks) are employed, the backup time achieved is

234 2 15 30.59 .

229.45Backup time achieved min

2

1

3

4

5

10 11

20

BANK - 1






2

1

3

4

5

10 11

20

BANK - 2






The rack dimension can be determined from the dimensions of the battery. The

dimension chart is given below

RACK DIMENSION

APPENDIX

Battery Configurations

The different configurations for arranging batteries in Battery room are shown

below

Sonnenschein SMF batteries

Dimensions