For advanced repairs or DIY charging, some models feature internal contact points (labeled C1 through C4) that represent the individual cell banks in the 5S (5 series) configuration: Usage Notes for DIY Adapters Simple Power
This is the common ground, the return path for the current. hart 20v battery pinout diagram better
A data/identification pin used by the charger to recognize the battery type and capacity. For advanced repairs or DIY charging, some models
Safety and protection circuits Hart batteries include protection circuitry: over-current cutouts, over/under-voltage protection, and temperature monitoring. The connector pins may be routed through the battery management system (BMS) so directly shorting pins or bypassing the BMS risks damage, fire, or injury. Always discharge and isolate properly before probing, and avoid shorting B+ to B−. The connector pins may be routed through the
For more official help, refer to the Hart Battery Support page or check the specific Operator's Manual for your tool model.
Knowing the pins is one thing. Knowing the behavior is better.