The Hart 20V battery uses a 5-pin interface to manage power delivery, temperature monitoring, and safe charging between the battery and the tool or charger Pinout Configuration
Looking at the battery with the terminals facing you, the pins are typically organized to handle both high-current power and low-voltage data: Positive (+):
The main power output providing approximately 20V DC. It is often located on the far right. TH (Thermistor):
A temperature monitoring pin connected to a 10kOhm thermistor. It signals the tool or charger if the battery is too hot or cold to operate or charge safely. ID (Identity):
A data connection that tells the tool or charger which specific battery type is connected to prevent overcharging or improper use. C (Control):
A control pin often used for internal management or additional signaling between the battery and tool. Negative (-): The main ground/return path for the electrical circuit. Advanced Monitoring and Charging
Internally, the battery contains five lithium-ion cells in series (5S). While the external tool interface uses 5 main pins, the internal Battery Management System (BMS) often uses additional contact points (marked C1, C2, C3, and C4) for balanced charging
. These points allow the charger to monitor and top off each individual cell, ensuring the pack stays healthy and doesn't develop dead cells over time. Safety Features Low Voltage Protection: This is typically handled by the hart 20v battery pinout diagram better
, not the battery itself. If you use an adapter to power DIY projects, you must add your own low-voltage cutoff to prevent permanent damage to the cells. Resetting:
If a battery fails to charge despite being at room temperature, it can sometimes be "reset" by placing it on a specific 4-port rapid charger for several minutes. Are you planning to build a DIY adapter for a specific project, or are you trying to a battery that isn't charging?
The pinout for a HART 20V battery typically consists of five main terminals used for power delivery, temperature monitoring, and tool identification. The primary power terminals are located at the outermost edges, while the inner pins provide safety and control signals to the charger and tool. Pin Identification and Functions
While specific markings can vary by battery size (e.g., 2.0Ah vs. 4.0Ah), the standard terminal arrangement includes the following:
Positive (+): The main power output terminal, typically providing ~20V relative to the negative terminal when fully charged.
TH (Thermistor): A temperature monitoring pin that connects to an internal NTC thermistor. This pin allows the charger and tool to detect if the battery is overheating or too cold to operate.
ID (Identification): A data/identification pin used by the charger to recognize the battery type and capacity. The Hart 20V battery uses a 5-pin interface
C (Control): A control terminal used for signal communication between the battery management system (BMS) and the tool or charger. Negative (-): The main ground or common return terminal. Internal Balance Contacts (C1–C4)
In addition to the main external pins, the battery pack contains internal contact points (labeled C1, C2, C3, and C4) used for balanced charging. These points allow the charger to monitor the voltage of individual cell groups within the 5S (5 cells in series) lithium-ion configuration: C1: ~4V (Cell 1) C2: ~8V (Cell 1 + Cell 2) C3: ~12V (Cells 1-3) C4: ~16V (Cells 1-4) Voltage Reference Table
When testing with a multimeter, these are the expected voltage readings between terminals on a healthy, charged battery: Terminal Pair Expected Voltage (Approx.) (+) to (-) 18V – 20.5V (+) to TH (-) to TH (+) to ID (-) to ID (-) to C
Are you trying to repair a battery that isn't charging, or are you looking to use the battery for a DIY project? Hart 20v Battery Pinout Wiring Diagram
The Hart 20V battery interface typically features five main pins that allow the battery to communicate with both tools and chargers to ensure safe operation and longevity. Hart 20V Pinout Details
According to technical measurements and user diagrams, the five pins are generally arranged as follows: Voltage (Relative to Negative) (+) Positive Main power output ~18V - 20V (Fully charged) TH (Thermistor) Temperature monitoring to prevent overheating ID Identifies the battery type to the tool or charger C (Control) Control signal for charging/protection (-) Negative Common ground / Return path Advanced Under-Voltage Detection
Some users have noted a more complex behavior for the positive terminals. Larger, "fat" positive pins are often found on high-draw tools like vacuums or drills. Quick Troubleshooting Tip If your HART battery won't
Dual Positive Pins: There may be a main positive and a smaller secondary positive for low-power connections.
Voltage Drop Safety: When the battery is nearly drained, the main positive may show ~16V while the secondary logic pin drops significantly (e.g., to ~5V), acting as an under-voltage cutoff to protect the cells from deep discharge. Balancing Contacts (Internal)
While the external interface shows five pins, the battery pack internally uses four additional contact points (often marked C1 through C4) for balanced charging. These points connect between individual cell groups, allowing a Hart 20V Fast Charger to ensure each cell is charged evenly to prevent premature failure.
Are you looking to build a DIY adapter or are you trying to troubleshoot a battery that isn't charging correctly?
HART 20-Volt 2-Amp Fast Charger (Battery Not Included) - Walmart
If your HART battery won't charge or run a tool:
✅ You CAN:
❌ You SHOULD NOT:
The TH pins are connected to an NTC Thermistor inside the battery pack.
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