Ben hooked his oscilloscope up to the mysterious "ID" pin. The signal wasn't a simple resistor ID. It was a digital pulse train.
Identifying pins on a Hart 20V pack (practical method) hart 20v battery pinout diagram better
Finally, a better pinout diagram fosters . The “second life” of power tool batteries is a growing movement. DIYers use old Hart battery packs to power soldering stations, portable speakers, RC cars, or emergency lighting. However, simply hooking a motor to the B+ and B- terminals bypasses the BMS’s low-voltage cutoff, leading to destroyed cells. A better pinout diagram shows the enterprising maker exactly how to interface with the BMS. It might illustrate a simple circuit using the ID pin to request power or explain how to simulate the tool’s “enable” signal. This turns a discarded Hart battery from waste into a sophisticated, rechargeable power station for any project. Ben hooked his oscilloscope up to the mysterious "ID" pin