| Terminal | Common Label | Function | Wire Color (Internal) | | :--- | :--- | :--- | :--- | | T1 | B+ | Battery Positive (+20V) | Red | | T2 | BS1 | Battery Status 1 (Thermistor) | White or Yellow | | T3 | ID | Battery Identification (Resistor to B-) | Blue or Green | | T4 | BS2 | Battery Status 2 (often unused or second temp sensor) | Black or Brown | | T5 | B- | Battery Negative (Ground) | Black |
Note: Some Hart batteries have only 4 physical terminals (missing T4). In that case, T2 remains the thermistor, T3 is the ID pin, and T4 is simply absent.
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).
How does HART compare to other brands? This table saves you hours of research. Hart 20v Battery Pinout Diagram
| Brand | Terminals | ID Method | Cross-Compatible? | |-------|-----------|-----------|-------------------| | HART 20V | 5 (B-, T2, T1, ID, B+) | 1-Wire serial (TTI proprietary) | No (with Ryobi/Milwaukee) | | Ryobi 18V | 6 (B-, T1, T2, ID, B+, HS) | Analog resistor (different Ω per Ah) | No – Physical slot different | | Milwaukee M18 | 7 (B-, T, C, B+, 3 balance) | Digital handshake + temperature | No | | DeWalt 20V | 4 (B-, C, TH, B+) | Single-wire proprietary (TD) | No |
Takeaway: HART is not a clone of any other battery. Even though TTI makes both HART and Ryobi, the BMS firmware is unique.
The HART 20V battery typically contains 5x 18650 cells in series (5S). To harvest: | Terminal | Common Label | Function |
Note: Many HART BMS boards have a proprietary IC that prevents voltage output if any cell is disconnected, even for a second. Proceed carefully.
HART does not publish engineering schematics. However, these resources are helpful:
For exact voltage curves and thermistor tables, you can reverse-engineer your own battery using a multimeter and a temperature gun. Note: Some Hart batteries have only 4 physical
This is the ground return path. To power a device, you connect your load between Pin 1 and Pin 5.
Below is the standard pinout configuration for Hart 20V Lithium-Ion batteries. Note that orientation is critical; we will use the standard orientation of the battery label facing you.