Ryobi40V

This is a basic analysis of how a Ryobi 40V smart charger (model number OP403) communicates with the battery's BMS to enable the charging FET.

Electronics

Pictures of the charger PCB are below:

PCB top side.

PCB bottom side.

The wall wart adapter is a 42V 1.5A rated switching converter, listed at 84W max from AC (though output is max 63W). The wall wart does the necessary CC/CV current limiting, with a ~44.2V open circuit voltage output when no battery is connected. Output is switched to the battery though a MOSFET.

Charging Sequence:

Battery insertion to charging start sequence.

Data detail:

Data packet detail.

The charger includes a 5V 1.5A buck based on a MP2487 (4.5-55V in, 220mOhm PFET, 1.5A max). The sticker claims 5V 2.1A output.