how to calculate the power consumption for battery?

Question

The battery is maintenance free sealed battery.What i need to know is the number of units that shall be consumed to charge a battery of say 7 AH

Answer 1

The energy storage of the battery in Joules is approximately the amp-hour rating, times the terminal voltage, times 3600 (seconds per hour).

The power to charge it depends on the rate at which you apply energy to the battery. Normally maintenance-free lead acid batteries should not be charged too quickly or they will become damaged. Normal rates of charge are listed as a fraction of the capacity (in amp hours), such as C/10 or C/20. This means you should apply charging current at 1/10th or 1/20th of the capacity. In your case 700 mA, or 350 ma.

Ideally, at a C/10 rate (700 mA), the battery would be charged from an 'empty' state to a fully charged state in 10 hours. The charging voltage is typically 110% of the terminal voltage, so the charging power would be:
0.7 Amp * terminal voltage * 1.1

The charging energy would be (in Joules):
0.7 * terminal voltage * 1.1 * 10 hours * 3600 sec/hour

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