There are 3rd party adapters available that allow you to use a DeWalt battery on a Hart tool, or vice versa.

While it is theoretically possible to rebuild a Hart battery by spot-welding new 18650 cells inside, .

Never short B+ to B-. Always use a fuse (5A-10A) and monitor cell voltage to avoid deep discharge below 15V total.

A communication or control pin often used for low-voltage protection or signaling.

If you are building a project or diagnosing a faulty tool, tell me or what symptoms your battery is showing . I can provide the exact wiring step or resistance value you need. Share public link

HART is not a clone of any other battery. Even though TTI makes both HART and Ryobi, the BMS firmware is unique.

Set your multimeter to DC Voltage. Place the red probe on (+) and the black probe on (-) . A fully charged healthy battery should read between 20.0V and 20.5V . A depleted but healthy battery should read around 15.0V to 16.0V . If it reads below 10V , one or more internal cell groups have likely failed or dropped too low to recover normally.

Typically reads around 10kΩ at room temperature (25°C / 77°F) relative to the Negative (-) terminal. The Low-Voltage Cutoff Warning

| Terminal Label | Shape/Size | Primary Function | Typical Voltage | |----------------|------------------|--------------------------------------|------------------| | (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) |

This usually indicates a communication error. Remove the battery, clean the metal terminals on the battery and the charger with a dry cloth, and reseat it. If the issue persists, try the reset method mentioned above.

Never bridge the and (-) pins with raw wires or metal objects. Doing so can bypass certain external safety features, melt the terminal housing, blow the internal permanent fuse, or rupture the cells. Custom DIY Applications and Power Adapters

Crucial for charging; generally ignored by basic tool adapters. Outer Slot Ground / Power Return

These readings confirm the "20V Max" marketing terminology: The battery's actual voltage is comprised of five series-connected cells, each with a nominal voltage of 3.6V-3.7V and a maximum charge voltage of 4.2V per cell. When fully charged, the total output reaches a peak of approximately 21.0V, which is rounded up to "20V Max" for marketing purposes.

Before you use a multimeter or attempt to bridge these pins, keep these facts in mind:

Hart shares its underlying platform engineering with Ryobi (both brands are manufactured by Techtronic Industries, or TTI). While the physical shape of the battery housings differs significantly—Ryobi uses a post-style battery whereas Hart uses a modern slide-style battery—their electronic communication systems share a similar logic.