Hart 20v Battery Pinout Diagram Site
This is the ground return path. To power a device, you connect your load between Pin 1 and Pin 5.
This is the primary output terminal. When fully charged, a "20V Max" battery actually outputs roughly 20 to 21 Volts. When depleted, it reads around 15V. The nominal voltage of the cells inside is 18V (5 cells in series, or 5S configuration).
The Hart 20V battery pack typically uses three main electrical contacts: Hart 20v Battery Pinout Diagram
Some packs also include additional alignment tabs or plastic shrouds for mechanical fit; only the metal contacts carry electrical signals.
Use B+ and B- to feed a 20V-to-5V USB buck converter (available on Amazon/eBay). The battery’s BMS will still protect against over-discharge if you run the USB port through the BMS output (not direct to cells). This is the ground return path
Below is the industry-mapped pinout for standard Hart 20V slide-pack batteries (view from the top of the battery, terminals facing you).
| Pin Number | Label | Function |
|------------|--------------|------------------------------------------------------------|
| 1 (Left) | B+ | Battery Positive (+), 20V Max (21V hot off charge) |
| 2 | CH or ID | Charge enable / Thermistor or ID resistor (depends on model) |
| 3 | C or S | Communication (SMBus Data line) – talks to charger & tool |
| 4 | B- Sense | Negative sense / Cell tap (sometimes unused) |
| 5 (Right) | B- | Battery Negative (-), ground | Some packs also include additional alignment tabs or
⚠️ Note: Hart batteries have at least 3 pins (B+, B-, and a third pin). Higher capcity packs (4Ah, 5Ah, 6Ah) include a 4th or 5th pin for balancing or communication.
