mAh to Wh calculation formula
E(Wh) = Q(mAh) × V(V) / 1000
The energy E in watt-hours (Wh) is equal to the electric charge Q in milliamp-hours (mAh), multiplied by the voltage V in volts (V), divided by 1000.
Wh = mAh x V / 1000
watt-hour = milliamp-hour × volt / 1000
Electric charge (Q) = 500mAh
Voltage (V) = 55V
Energy (E) = 500mAh x 55V / 1000 = 27,5Wh