Power Consumed by UPS Batteries

Not every situation can be defined by a mathematical formula.

Not every problem can be solved by a mathematical formula.

If you are compiling load information for a transformer, to be safe, use the FLA (full load amp) of everything that the transformer will supply, plus a safety factor, plus any anticipated future loads.

This figure can be calculated by simple addition.

To calculate the power consumed by UPS batteries for the case 2 (boost charge), additional information is required such as battery ampere-hour (AH), battery type, battery voltage, charger efficiency, battery charging time etc.

Let's assume,

Battery capacity: 200 AH, Battery Type: Lead Acid, Battery voltage: 12 V, Charger eff: 90%, Charging time: 8 Hour

Battery discharged 90%, hence discharged AH 200 x 0.9 = 180 AH

Battery charging current for charging it back to full = (180 x 1.1) / 8 = 25 A

(1.1 is a factor for Lead Acid type battery, 8 is the charging time)

Charger output capacity required 12V, 25A

Charger output watts: 12 x 25 = 300 watts

Charger input watts: 300 / 0.9 = 333 watts. This is the power required by UPS for boost charging.

For case 1 (tickle charge), you can consider 10% of this capacity. Hope it helps.

Regarding the Heat, you need the efficiency of the overall UPS (charger and inverter). If you don't have heat, consider it at least 30% of the UPS capacity.

- MS