DC UPS Battery Sizing
The battery amperes–hour capacity shall be computed by the following formula:
𝑨𝑯(𝑼𝑷𝑺)=𝑳×𝑩𝑻×𝑻𝑪×𝑨𝑭×𝑫𝑭
AH(UPS) – Battery Capacity
L – Load Current
BT – Battery Backup Time (Hrs)
TC – Temperature Compensation Factor
AF – Battery Aging Factor
DF- Design Factor
DC UPS Battery Capacity:
𝐴𝐻(𝑈𝑃𝑆)=𝐿×𝐵𝑇×𝑇𝐶×𝐴𝐹×𝐷𝐹
Example:
L= 45.45A, BT= 4.00 Hrs, TC = 1, AF = 1.25, DF= 1.10
𝐴𝐻(𝑈𝑃𝑆)=45.45×4×1×1.25×1.10
𝑨𝑯(𝑼𝑷𝑺)=𝟐𝟒𝟗.𝟗𝟕 𝑨𝒎𝒑𝒆𝒓𝒆−𝒉𝒐𝒖𝒓
(For Four Hours Battery Back-up)
DC UPS Battery Charging Sizing
The current rating of UPS battery charge sizing shall be calculated by the following formula
𝐴𝐻(𝑏𝑐)=(𝑆𝐹×𝐿)+((𝐵𝐼𝐹)×(𝐴𝐹/𝑅𝑇))
Where,
A(bc) – Ampers rating of charger
SF – Service Factor
AH – Battery Capacity
RT – Recharge Time
L – Load Current
BIF – Battery in efficiency factor
Example
SF- 1.10, AH – 270.00, RT- 8.00 hrs, L – 45.45A, BIF – 1.15
𝐴𝐻(𝑏𝑐)=(1.10×45.45)+((1.15)×(27/08))
𝐴𝐻(𝑏𝑐)=88.80 𝐴𝑚𝑝𝑒𝑟𝑒𝑠
