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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]
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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
Tier 2 = 20 batteries
ARRANGEMENT OF BATTERIES IN BATTERY ROOM
OVERALL TOTAL = 40 batteries
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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
Double Row Double Tier
Tier 1 = 20 batteries
Tier 2 = 20 batteries
TOTAL = 40 batteries
ARRANGEMENT OF BATTERIES IN BATTERY ROOM
2
1
3
4
5
10 11
20
BANK - 2
Double Row Double Tier
Tier 1 = 20 batteries
Tier 2 = 20 batteries
TOTAL = 40 batteries
OVERALL TOTAL = 80 batteries
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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
Discharge rating per battery A
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
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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
Double Row Double Tier
Tier 1 = 20 batteries
Tier 2 = 20 batteries
ARRANGEMENT OF BATTERIES IN BATTERY ROOM
OVERALL TOTAL = 40 batteries
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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
Discharge rating per battery A
Considering Design Margin Ageing Factor
Discharge rating per battery A
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
Double Row Double Tier
Tier 1 = 20 batteries
Tier 2 = 20 batteries
TOTAL = 40 batteries
ARRANGEMENT OF BATTERIES IN BATTERY ROOM
2
1
3
4
5
10 11
20
BANK - 2
Double Row Double Tier
Tier 1 = 20 batteries
Tier 2 = 20 batteries
TOTAL = 40 batteries
OVERALL TOTAL = 80 batteries
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The rack dimension can be determined from the dimensions of the
battery. The
dimension chart is given below
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RACK DIMENSION
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APPENDIX
Battery Configurations
The different configurations for arranging batteries in Battery
room are shown
below
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Sonnenschein SMF batteries
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Dimensions