Laptop Battery Capacity:
How does whr or simply Wh converts to mah?
converting watt-hour (Wh) to milliampere-hour (mAh).
Watt-hour to milliampere-hour calculation formula
The electric charge Q(mAh) in milliampere-hours (mAh) is equal to the energy E(Wh) in watt-hours (Wh) times 1000 divided by the voltage V(V) in volts (V):
Q(mAh) = E(Wh) × 1000 / V(V)
So milliamp-hour is equal to watt-hour times 1000 divided by volts:
milliamp-hour = watt-hour × 1000 / V
or
mAh = Wh × 1000 / V
Watt Hour = Volts x Amps x time in hours
Watts = Volts x Amps; Amps = Watts/Volts
Watt Hour = Volts x Amps x time in hours
Watts = Volts x Amps; Amps = Watts/Volts
Example
Find the electric charge in milliamp-hour when the energy consumption is 3 watt-hour and the voltage is 5 volts.
The electric charge Q is equal to 3 watt-hour times 1000, divided by 5 volts:
Q = 3Wh × 1000 / 5V = 600mAh
Depending on the cell connection scheme, the nominal Lithium Ion battery pack voltage can vary from 7.2 V to 14.8 V (typical voltages for major brands are: 11.1 to 14.8 V for Dell laptop battery, 10.8 to 14.8 V for Toshiba, Apple, Gateway and IBM laptop batteries, 7.4 to 14.8 V for Sony, 7.2 to 14.8 V for HP, 14.4-14.8 V for Compaq). Note that the voltage rating of a laptop power supply is not necessarily the same as nominal battery voltage.
Say a battery is rated 53 WHr and the nominal voltage is 12.5 volts.
53 WHr/12.5 Volts = 4.24 Amp-Hr
4.24 amp-Hr x 1000 milli-amp/amp= 4,240 mah
Depending on the cell connection scheme, the nominal Lithium Ion battery pack voltage can vary from 7.2 V to 14.8 V (typical voltages for major brands are: 11.1 to 14.8 V for Dell laptop battery, 10.8 to 14.8 V for Toshiba, Apple, Gateway and IBM laptop batteries, 7.4 to 14.8 V for Sony, 7.2 to 14.8 V for HP, 14.4-14.8 V for Compaq). Note that the voltage rating of a laptop power supply is not necessarily the same as nominal battery voltage.
Say a battery is rated 53 WHr and the nominal voltage is 12.5 volts.
53 WHr/12.5 Volts = 4.24 Amp-Hr
4.24 amp-Hr x 1000 milli-amp/amp= 4,240 mah
