A battery must be able to generate power consistently over a given period. Power is measured in Watts (W) and calculated using the equation shown below. Watt hours (Wh) define how long this power can be delivered.

It’s the relationship between voltage and current that counts. A big voltage doesn’t necessarily mean big power — there also has to be enough current (and vice versa). In the instance of battery powered technology the current (A) depends on the cell types being used, the condition and quality of the cells and the control system put in place to manage them.

- Power (Watts) = Voltage (V) x Current (A).

To work out how long the power can be delivered, the following equation can be used:

- Energy (Wh) = Voltage (V) x Capacity (Ah).

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