A battery is charged by first charging the battery at a constant current during a first time interval, and then charging the battery at a varying current during a second time interval. The battery can be a lithium-ion battery, and the charging uses a kinetic model. The kinetic model models the battery having an indiffused well having a capacity c, and a diffused well having a capacity 1−c, and the indiffused well is filled directly by the current, and the diffused well is filled only from the indiffused well via a valve with constant inductance.