Hart 20v Battery Pinout Diagram May 2026

A: Only if you have the BMS communication protocol decoder. Without it, the BMS won’t enable charging. Stick to the official charger.

Hart 20V batteries utilize a proprietary block-style form factor. Unlike the slide-on rails of Dewalt or the stem-style of Black+Decker, Hart batteries usually feature a top-mounted interface with exposed contact pads.

If you only need to power a light or motor and do not care about the smart features: Hart 20v Battery Pinout Diagram

| Terminal Label | Shape/Size | Primary Function | Typical Voltage | |----------------|------------------|--------------------------------------|------------------| | B- (Neg) | Large flat slot | Main negative / Ground | 0V (Reference) | | T2 | Small square pin | Temperature Sensor (Thermistor 2) | ~0.8V - 2.5V | | T1 | Small square pin | Temperature Sensor (Thermistor 1) | ~0.8V - 2.5V | | ID | Small square pin | Battery Identification / Data (1-Wire) | 0V - 5V (PWM) | | B+ (Pos) | Large flat slot | Main positive (Pack voltage) | 20V (Nominal) |

Note: Some lower-capacity HART 20V batteries (2.5Ah) may lack the second temperature pin (T2) and have only 4 terminals: B-, T1, ID, B+. A: Only if you have the BMS communication protocol decoder

If you leave a HART battery in a tool until it dies completely, the BMS may enter deep sleep (0V at B+). Trickle charging via B+ and B- won’t work because the BMS’s charge FET is off.

Solution (Use at your own risk):
Briefly apply 18V-20V from a known good battery directly to the internal cell group positive (bypassing the BMS for 3 seconds). This wakes the BMS. Then insert into official charger immediately. Without the ID signal, this won’t work. Orientation tip: When the battery is standing on

If you are repairing a Hart 20V battery, building an adapter, or troubleshooting a charger, understanding the pinout is critical. Unlike simple NiCad packs, modern lithium-ion batteries use a circuit board (BMS) to monitor temperature and voltage.

Below is the complete pinout diagram for the standard Hart 20V Lithium-Ion Battery Pack (Models: HPLB01, HPLB02, HPLB04, etc.).

Imagine looking at the battery’s connector slot. The terminals run along the top edge:

  [ B- ]  [ T2 ]  [ T1 ]  [ ID ]  [ B+ ]
    |       |       |       |       |
  Large   Small   Small   Small   Large
  Slot    Pin     Pin     Pin     Slot
  (Left)                          (Right)

Orientation tip: When the battery is standing on its base (the side with the fuel gauge button), the B- terminal is on the far left, and B+ is on the far right.