battery ah sizing claculation
DESCRIPTION
Choosing the proper battery for the application is very imperative. The method for sizing these batteries utilizing the various battery manufacturers’ data available for sizing is described in this document.TRANSCRIPT
-
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
Tier 2 = 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
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
-
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
-
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
-
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
-
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