battery-charger-fuel-gauge-integration

# Battery Charger and Fuel Gauge Integration ## Overview Use this skill to bring up a Li-ion/LiPo charger IC (TI `BQ24xxx`/`BQ25xxx`) and a fuel gauge (TI `BQ27xxx` Impedance Track, or Maxim/Analog `MAX1704x` ModelGauge, e.g. `MAX17048`) over I2C. The hard parts are keeping the charger in host mode past its watchdog, and getting an accurate SOC before the gauge has a matching battery profile. ## When To Use Use this skill when: - Charging never starts or restarts in a loop: check input current limit (`IINLIM`, `REG00[2:0]`), `EN_HIZ`, the `CE` pin, and the I2C watchdog resetting registers to default. - The charger reports faults: `REG09` latched faults, `NTC_FAULT` (`REG09[2:0]`, with a real thermistor such as `103AT` on the `TS` pin), safety timer expiration, or JEITA temperature de-rating. - SOC from `BQ27441`/`MAX17048` is wrong or jumps at power-up: profile not loaded, no learning cycle, or bad OCV calibration. - I2C reads to the charger/gauge fail or the wrong 7-bit address is used. Do not use this skill when the I2C bus itself is dead (no ACK on any address) or the board rails are wrong; debug the bus and power tree first with `hardware-interface-debug`. ## First Questions Ask for: - Exact charger and gauge part numbers, cell count/chemistry, pack capacity (mAh), and charge voltage (4.2 V vs 4.35 V — picks `BQ27441-G1A` vs `-G1B`). - 7-bit I2C addresses, bus speed, and pull-up values; whether `INT`/`GPOUT` is wired. - NTC/thermistor part and TS resistor network...