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.
