Li-Ion Capacity: mAh, Watt-Hours and Runtime

Nominal watt-hours can be calculated when both voltage and charge capacity refer to the same battery. The relationship is Wh equals volts multiplied by ampere-hours, and one thousand mAh equals one Ah. F10 publishes 3.7 V and 400 mAh in its battery-capacity field. Converting 400 mAh to 0.4 Ah gives 3.7 multiplied by 0.4, or a nominal 1.48 Wh. This is an arithmetic energy estimate from the published ratings, not a measured delivered-energy result. The distinction matters when comparing products at different voltages because identical mAh values can represent different nominal energy.

Capacity, charging time and runtime describe different stages of the energy system. Capacity concerns stored charge, charging time concerns replenishment under stated conditions, and runtime concerns energy consumption during operation. Heating, vibration and electrical pulse functions can impose different loads, while conversion losses and low-battery cutoffs affect usable energy. F11 publishes a 400 mAh battery and about 105 minutes of working time; F100 publishes 1000 mAh and up to 110 minutes. These catalog estimates do not establish identical test conditions, so their ratio cannot be treated as a battery-efficiency ranking. A larger battery can support a higher load rather than a proportionally longer session.