RE: Wio Terminal - Battery Fuel Gauge

Jan Cumps — Fri, 08 Jan 2021 17:59:26 GMT

I've used a bq27510-G2. Time to review that again. These gauges are a great way to keep track of charge and health...

RE: Wio Terminal - Battery Fuel Gauge

genebren — Fri, 08 Jan 2021 16:31:30 GMT

Interesting device. The datasheet on the BQ27441 mentions a Coulomb counter, which would imply that the charge and discharge currents (mA) are being used to accumulate the charge over time (mAH) to determine the actual battery charge state. In a product that I worked on we did the same sort of process, with current and voltage monitoring, to drive a charge indicator (LEDs). When properly calibrated we were able to get a pretty good readout of the remaining charge in the battery.

TI has a white paper (slpy002) that describes in better detail their ImpedanceTrack[emoticon:7d377b609b6f44bf9290e3d8a0b9a733] algorithms, which appear to use Coulomb counting, impedance measurements, open-circuit battery voltages and various table to predict the battery charge level. The Aging value seems to be based on long term changes in the measured capacities across multiple charge/discharge cycles, so you might have to wait a bit to see a change in that reading.

With Li-Ion batteries, the listed capacity can vary widely compared to the actual capacity of the battery. The displayed capacity of 584mAH is within ~10% of the rated capacity, so this is not too surprising.