an identification device associated with a code that identifies a specified charging protocol method, said identification device being a plug-in device releasably connected to a processor, said identification device independent of the battery, said identification device not physically attached to or housed with the battery when said identification device is connected to said processor;

a charger circuit including a power conversion circuit and a switch, said power conversion circuit configured to connect to an external power source, said power conversion circuit having an output providing power to said switch, said switch generating a variable duty cycle pulse width regulation output, said charger circuit configured to electrically connect to the battery;

a processor in communication with said switch, said processor programmed to execute a process for charging the battery, said process including reading a code identifying a specified charging protocol method, selecting a charging protocol corresponding to said code, controlling said switch to charge the battery in a manner determined by said charging protocol, monitoring to detect a replacement of said identification device with the battery remaining connected to said charger circuit, and after detecting said replacement, said process steps of reading said code, selecting said charging protocol, and controlling said switch are performed with a new code associated with a replacement identification device; and

whereby said apparatus applies said charging protocol to the battery by switching in output of said power conversion circuit.