K- factor

BATTERY CAPACITY CALCULATIONS ( 2V Standby range) Example

Considerations : System rating : 200 KVA Inverter efficiency : 96 % *No of cells : 192 nos. ( 384V DC bus voltage) End cell voltage : 1.75 VPC ,ie., 336 V Back up required : 30 mins Operating temp. : 15 DegC Load pattern : Constant

* In typical cases, the no. of cells can be arrived at by dividing the max charger voltage / max. recommended float voltage.

Capacity calculation for VRLA type (NMST) 2 V cells: Max. discharge Current = KVA(UPS rating) X 1000 X power factor ECV X Inverter Efficiency X No of cells =

200 X 1000 X 0.8 1.75 X 0.96 X 192 = 496 Amps Capacty factor for 30mins backup to ECV of 1.75 Volts = 1.389 ( from capacity factor table ) Hence Calculated capacity = 496 X 1.389 = 689 AH Final Capacity =((Calculated capacity) x Kt x KD)/A.F where Kt = Temperature correction factor KD = Design margin A.F = ageing factor Kt = 1 + ((27 - op.temp) x CT)/100, where CT is temperature correction factor at C-10, which is 0.43 for standby range KD = Design Margin (minimum of 10%) A.F = Ageing factor of 0.8 ( For Plante' , this is 1) Hence final capacity = (689 x (1+(12x0.43)/100) x 1.1) / 0.8 = 996.26 Ah NMST 1000Ah capacity can be recommended

Capacity calculation for Tubular type 2 V cells: Max discharge current remains same as above , i.e., 496 Amps Capacity factor for 30 mins back up to 1.75 end cell voltage = 1.46 (refer capacity factor table) Calculated capacity= 496 X 1.46 = 724 Ah approx. The Final capacity can eb derived the same way mentioned above by applying temperature correction, design margin & ageing factor.

Capacity calculation for Plante type 2 V cells: Again the max discharge current is 496 Amps. Capacity factor for 30 minutes (refer capacity factor table) is 1.16 Hence calculated capacity = 496 X 1.16 = 575 Ah The Final capacity can eb derived the same way mentioned above by applying temperature correction, design margin , except that the ageing factor. for plante' should be considered as 1.

at voltage.

BATTERY CAPACITY CALCULATIONS ( 12V monobloc range) Example

Considerations : System rating : 20 KVA Inverter efficiency : 96 % No of cells : 192 nos( 384V DC bus voltage) End cell voltage : 1.70 VPC Back up required : 1 hr Load pattern : Constant

Capacity calculation for VRLA 12 V monobloc (EP - Powersafe): Max. discharge Current = KVA(UPS rating) X 1000 X power factor ECV X Inverter Efficiency X No of cells =

20 X 1000 X 0.8 1.70 X 0.96 X 192 = 51.06 Amps Capacty factor for 1 hr backup to ECV of 1.70 Volts = 1.49 ( from capacity factor table ) So Capacity required

= 51.06 X 1.49 = 76.08 Ah

HENCE EP80-12 CAN BE RECOMMENDED

Capacity calculation for vented type 12 V monobloc (EL tubular): Max discharge current remains same as above , I.E., 51.06 Amps Capacty factor for 1 hr backup to ECV of 1.75 Volts = 2 ( from capacity factor table ) So Capacity required = 51.06 X 2 = 102.12 AH (approximately)

HENCE,nearest type, 6EL100 CAN BE RECOMMENDED Note : In both the above cases , the temperature correction has not been considered. It can be calculated the same way it is shown for 2V standby batteries.

Capacity Calculations for multiple load pattern Assumptions Battery required = VRLA Cut-off voltage = 1.85Vpc Load Pattern I3 = 60A

Current A

I1 = 40A

I2 = 20A

t1 = 30 min

Time t t2 = 120 min t3 = 30 min

Operating Temp = 20 Deg C Design Margin required = 20% A.F = Ageing factor (0.8 for VRLA)

Capacity =(( I1 x F1 + (I2-I1) x F2 + (I3 - I2) x F3) x Kt x KD) / A.F Where T 1 = t1 + t2 + t 3 / T 2 = t2 + t3 / T 3 = t3 F1 = Cap factor for T1 / F2 = Cap factor for T2 / F3 = Cap factor for T3 Kt = 1 + ((27 - 20) x CT)/100, where CT is temperature correction factor at C-10, which is 0.43 KD = Design Margin of 10%

Capacity = ((40 x 4.219 + (-20 x 2.703) + 20 x 1.760) x 1.05 x 1.2) / 0.8 = 236.09 Ah Nearest available capacity is EPST240 Ah

Capacity factor for VRLA 2V type Final volt v/cell 1.85 1.80 1.75 1.70 1.65 1.60

1 min

0.417 0.412 0.408 0.398

5 mins

0.625 0.609 0.592 0.572

15 mins

30 mins

1.490 1.241 1.110 1.020 0.960 0.920

1.760 1.499 1.389 1.311 1.258 1.225

60 mins 2.110 1.812 1.661 1.570 1.511 1.471

90 mins 2.703 2.342 2.179 2.070 2.008 1.969

2 hrs 3.195 2.809 2.653 2.538 2.457 2.398

3 hrs 4.219 3.731 3.521 3.401 3.268 3.185

4 hrs 5.181 4.630 4.386 4.237 4.132 4.000

5 hrs 6.173 5.556 5.319 5.128 4.975 4.831

6 hrs 7.194 6.494 6.173 5.952 5.814 5.650

8 hrs 9.009 8.197 7.937 7.692 7.463 7.299

10 hrs 10.753 10.000 9.615 9.259 9.091 8.929

Capacity factor for Vented 2V tubular type (NDP) Final volt v/cell 1.85 1.80 1.75 1.70 1.65 1.60

1 min

5 mins

15 mins

20 mins

30 mins

45 mins

1 hr

2 hrs

3 hrs

4 hrs

5 hrs

6 hrs

7 hrs

8 hrs

9 hrs

10 hrs

1.60 1.10 0.86 0.68 0.58 0.53

1.65 1.20 0.95 0.77 0.67 0.60

1.95 1.34 1.09 1.03 0.91 0.72

2.10 1.54 1.30 1.12 1.00 0.92

2.35 1.74 1.46 1.28 1.17 1.10

2.50 2.02 1.77 1.61 1.50 1.44

2.85 2.31 2.00

3.55 3.25

4.50 4.18

5.25

6.10

6.85

7.80

8.55

9.30

10.00

Capacity factor for Vented 2V tubular type (HDP) Final volt v/cell 1.85 1.80 1.75 1.70 1.65 1.60

1 min

5 mins

10 mins

20 mins

30 mins

45 mins

1 hr

2 hrs

3 hrs

4 hrs

5 hrs

6 hrs

7 hrs

8 hrs

9 hrs

10 hrs

1.38 0.96 0.74 0.60 0.51 0.46

1.44 1.04 0.82 0.68 0.58 0.52

1.54 1.16 0.96 0.80 0.70 0.63

1.74 1.34 1.13 0.98 0.87 0.80

2.04 1.62 1.37 1.20 1.10 1.03

2.12 1.87 1.65 1.51 1.41 1.35

2.50 2.02 1.67

3.30 2.81

4.15 3.70

5.05

5.92

6.75

7.70

8.48

9.25

10.00

Capacity factor for Vented 2V Plante type cells Final volt v/cell 1.85 1.80 1.75 1.70 1.65 1.60

1 min

5 mins

10 mins

15 mins

20 mins

30 mins

45 mins

1 hr

2 hrs

3 hrs

4 hrs

5 hrs

6 hrs

7 hrs

8 hrs

9 hrs

1.18 0.94 0.75 0.63 0.52 0.46

1.28 1.00 0.82 0.68 0.58 0.50

1.30 1.04 0.86 0.72 0.63 0.56

1.38 1.10 0.92 0.80 0.70 0.64

1.48 1.20 1.00 0.86 0.77 0.72

1.62 1.34 1.16 1.04 0.94 0.88

1.74 1.48 1.32 1.22 1.15 1.10

1.80 1.60 1.54

2.80 2.67

3.80 3.59

4.65

5.60

6.50

7.45

8.25

9.10

Capacity factor for VRLA 12 Volt monobloc. Final volt v/cell 1.80 1.70 1.65 1.60

30 secs

1 min

2 mins

3 mins

4 mins

5 mins

7 mins

10 mins

15 mins

20 mins

30 mins

1 Hr

90 mins

2 Hrs

0.25 0.18 0.15 0.13

0.26 0.20 0.17 0.15

0.26 0.20 0.19 0.18

0.27 0.23 0.22 0.20

0.29 0.25 0.24 0.23

0.31 0.28 0.26 0.25

0.36 0.33 0.31 0.30

0.43 0.40 0.37 0.36

0.56 0.53 0.50 0.48

0.67 0.63 0.61 0.59

0.91 0.87 0.83 0.80

1.56 1.49 1.45 1.43

2.38 2.08 2.00 1.96

2.78 2.50 2.44 2.38

Capacity factor for Tubular 12 Volt monobloc. Final volt v/cell

1 hr 1.8

1.75

2

2 hrs

3 hrs

4 hrs

5 hrs

6 hrs

7 hrs

8 hrs

9 hrs

10 hrs

3.16

4.14

5.13

6.02

6.82

7.61

8.42

9.18

10

10 hrs 10.00