Information required for battery capacity calculation
We need below basic information for a precise battery capacity calculation.

- nominal voltage of the system	- load current
- standby period	- maximum voltage(for charging)
- minimum voltage	- temperature range
- battery layout and available space	- physical condition

Float Voltage Operation
In these conditions the float voltage, being the voltage at which the general load circuit will operate, then a decision will have to be reached on the cell float voltage needed to maintain the battery in the required condition.

The most commonly used float voltages are 1.40-1.48 voltage per cell, but the exact figure has to be related carefully to the circumstances.

Example
An Semicad battery is required to maintain an inverter load of 50KVA at 0.8 power factor for a back up time of 30minutes, at normal temperature. The D.C. voltage to the inverter operates within the limit of 265 voltage with the battery on float charge to a minimum of 202 voltage at end of back up time. The inverter has an 85% efficiency.

We shall choose the battery with capacity equal or just above.
Determination Battery Capacity - KMP range
From our catalog data (PAGE7) the cell type is KMP300.

∴ Battery would comprise 184cells Semicad type KMP300.

The Number of Cells in a battery
The number of cells in a battery may be determinded by simply dividing the norminal voltage of the system by the norminal voltage of a cell(1.2V).