A method of charging a battery is provided that alters the amount of energy stored within the battery based upon a temperature profile across time. Battery materials and components, like liquid
electrolyte or electrodes for instance, can be damaged when a
rechargeable cell is exposed to elevated temperatures for extended amounts of time, thereby reducing the overall amount of energy that may be stored within the
cell. This method monitors
stored energy capacity and temperature. When a fully-charged
cell is held at a temperature that exceeds a predetermined temperature threshold for an extended amount of time, the method discharges the
cell, thereby reducing the amount of energy stored within the cell. For example, when a single,
lithium-
ion cell is maintained at 4.2 V for over 10 hours, the method will
discharge the cell by roughly 1% or 50 mV. The
discharge may be either automatic, or at the prompt of a user.