A method and a system for accurately reporting battery capacity that do
not rely on a coulomb counter are disclosed herein. The method comprises
the steps of determining if the battery is in a transition phase and
determining the battery capacity based on a transition phase battery
capacity model when the battery is in the transition phase. The
transition phase occurs upon one of attachment of the battery to a power
source and disconnection of the battery from the power source. The
behaviour described by the transition phase battery capacity model
approaches the behaviour of real transition phase battery capacity so as
to minimize the error of the determined battery capacity. The method and
system accurately report battery capacity during a transition phase from
discharging to charging and a transition phase from charging to
discharging.