If your battery requires the thermistor circuit to activate:
These pins are used for the "Smart" features.
A communication or control pin often used for low-voltage protection or signaling.
If you run a custom wire adapter from the battery terminals, install an inline fuse holder on the positive wire. Use a fuse rated slightly below the maximum capacity of your wire (e.g., a 20A or 30A automotive fuse) to protect against accidental short circuits. Hart 20v Battery Pinout Diagram
Note that low-voltage cutoff is often handled by the tool, not the battery itself. When using these batteries for DIY projects, ensure you include a Low Voltage Disconnect to prevent permanent battery damage from over-discharge. Resetting the Battery: If a battery fails to charge, placing it on a Hart 4-Port Fast Charger for a few minutes can sometimes trigger a reset. Compatibility:
You don’t need the data lines to discharge a Hart battery carefully. You only need B+ and B-.
If you are using a Hart 20V battery to power a custom robot, Power Wheels upgrade, or a 12V-24V inverter, use these implementation rules: If your battery requires the thermistor circuit to
This terminal is part of a thermal monitoring circuit.
Respect these connections, never bypass safety features, and you’ll get years of reliable service from your Hart 20V ecosystem.
Switch your multimeter to Resistance (Ohms) mode. Measure between the T pin and the Negative pin . At room temperature (approx. 21°C / 70°F), you should see a stable reading (usually around 10kΩ). If the meter reads infinite resistance (open circuit) or zero resistance (short circuit), the internal temperature sensor is broken, rendering the pack unusable without internal repair. Conclusion Use a fuse rated slightly below the maximum
Are you planning to build a custom or just troubleshooting a charging issue ? Hart 20v Battery Pinout Wiring Diagram
(Note: orientation can vary by model; confirm visually on your pack.)
The "20V" designation is a marketing term representing the measured without a workload. The actual working voltage under load is 18 Volts nominal .