The firmware exposes no charging flag, so charging is inferred from the
terminal-voltage trend. The old test compared the first and last samples
in the window against a 15 mV threshold — but a single-cell LiPo sags
tens of millivolts under each LoRa transmission and springs back when the
radio idles, so a lone sagged sample at either endpoint read as a
+tens-of-mV "rise" and the gauge falsely showed charging on a discharging
or resting pack.
Read the trend from the median of the window's older half against the
median of its newer half (discarding the transient sag/recovery spikes)
and require a large, sustained rise, with hysteresis: hard to start
(25 mV), held while still clearly climbing (8 mV), and dropped the moment
the pack goes flat — topped off or unplugged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Jean-Pierre MartineauandClaude Opus 4.8
e73cea9f42