Bq40370
Despite its closed nature, a thriving community of battery repair technicians and hobbyists has emerged around the BQ40370. Forums like are hubs for sharing knowledge and troubleshooting these chips.
| Feature | | bq40z50 / bq40z80 | bq28z610 | | :--- | :--- | :--- | :--- | | Algorithm | Impedance Track | Impedance Track | Impedance Track | | Cell Count | 2S – 4S | 2S – 4S | 1S – 2S | | Target Market | High Accuracy, Industrial/Medical | General Purpose, High Volume | Compact Packs, Wearables | | Balancing | Passive Balancing during Charge/Rest | Passive Balancing | Passive Balancing | | Key Differentiator | High integration, robust safety profile. | Successor device with similar features. | Lower cell count, smaller form factor. |
| Pin(s) | Name | Description | |--------|------------|------------------------------------| | 1–4 | VC1–VC4 | Cell voltage inputs (VC1 = lowest) | | 5 | VSS | Ground (negative of lowest cell) | | 6 | REG25 | 2.5V regulator output (cap to GND) | | 7 | TS1 | Thermistor input 1 (battery temp) | | 8 | TS2 | Thermistor input 2 (optional) | | 9 | SDA | I²C data | | 10 | SCL | I²C clock | | 11 | BAT | Pack positive voltage (for AFE) | | 12 | PACK | Pack+ terminal (through protection FETs) | | 13 | DSG | Discharge FET gate drive | | 14 | CHG | Charge FET gate drive | | 15 | SRP | Sense resistor positive | | 16 | SRN | Sense resistor negative | | 17–18 | NC / ALERT | Alert output (optional) | | 19–24 | Other | Cell balancing control, test pins | bq40370
The chip belongs to Texas Instruments' elite family of "Impedance Track" gas gauges. This methodology allows the silicon to map the internal resistance of the battery cells in real-time, calculating exact remaining capacity, state-of-charge (SoC), and overall health (State of Health - SoH) with minimal margin of error.
Because it is a protected, custom chip, specialized tools are required for any "reset" or calibration tasks: : Despite its closed nature, a thriving community of
Failure to perform this learning cycle results in inaccurate battery percentage reporting (e.g., the device shutting down while reporting 20% battery remaining).
The is a highly specialized, proprietary battery management and gas gauge Integrated Circuit (IC) developed by Texas Instruments . Primarily found in premium laptop battery packs—most notably across various Dell laptop series (such as the WDX0R, 3DDDG, and F3YGT battery models)—the BQ40370 plays a critical role in monitoring cell health, managing safety thresholds, and reporting accurate state-of-charge (SoC) metrics to the host computer. | Successor device with similar features
The BQ40370, like all smart battery gauges, operates in a "sealed" state by default. In this mode, some configuration data is protected from reading or writing. Performing calibration or repair requires sending an "unseal" command. This security feature is designed to prevent tampering, but the unseal method for many custom chips is known within the repair community. However, for a battery that has been permanently locked due to a critical failure, the chip may not be recoverable via software alone.
However, its complexity often leads to common repair hurdles:
(System Management Bus) protocol, reporting battery health, cycle counts, and charging requests. Repair and Customization Challenges