Bq40370 ❲2026❳

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.

Because it is a custom chip, the BQ40370 is known among laptop repair technicians for several common challenges: bq40z60 Programmable Battery Management Unit bq40370

| 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 | Despite its closed nature, a thriving community of

| Symptom | Likely cause | Solution | |----------------------------|----------------------------------------|----------| | SOC jumps from 20% to 0% | Wrong EDVx or CEDV coefficients | Re-run CEDV calibration | | FETs not turning on | AFE not powered (missing BAT voltage) | Check BAT pin ≥ 6V | | I²C no response | Device sealed and not addressed correctly | Unseal via 0x44 command | | Overvoltage protection too sensitive | Cell imbalance or wrong OV threshold | Balance cells, adjust OV | | Temperature reading wrong | Incorrect thermistor β value in config | Set correct β in data flash | Despite its closed nature