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[Juan Manuel]

Hi Chris, Heiko,

While bringing up a couple of Powkiddy RK3566 handhelds I ran into a
battery problem that turns out to be in the device trees, and it has
already cost me two packs, so I'd like to get it fixed for everyone.

Both battery nodes charge the cell above its own declared full voltage:

rk3566-powkiddy-rk2023.dtsi (inherited by the RGB10 Max 3):
constant-charge-voltage-max-microvolt = 4250000 (4.25 V), but
voltage-max-design-microvolt and the ocv-capacity-table-0 100% point
are both 4172000 (4.172 V).

rk3566-powkiddy-x55.dts: constant-charge-voltage-max-microvolt =
4300000 (4.30 V), but voltage-max-design-microvolt and the
ocv-capacity-table-0 100% point are both 4138000 (4.138 V).

So the charger drives each cell ~80–160 mV past its own OCV-100% point
on every cycle. On a standard 4.2 V Li-Po that is an overcharge: it
raises the cell's internal resistance and kills the pack early. The
symptom is textbook — the pack reads a normal voltage/SoC while on the
charger but collapses under load and shuts the device off the moment
it's unplugged. I lost two packs to this before tracing it to the DT;
capping the charge voltage at 4.2 V (verified at the rk817 CHRG_OUT
register) stopped the damage, and a third, already-degraded pack
stabilised.

Patch 1 also corrects the RGB10 Max 3 design capacity: it ships a 4000
mAh cell but inherits the 3151 mAh value from rk2023.dtsi. I did this
as a per-board override so I don't touch the shared profile, which may
well be correct for the RGB30 and other rk2023 users.

One thing worth a look on your side: the shared
rk3566-powkiddy-rk2023.dtsi default itself (4.25 V against a 4.172 V
OCV-100% point) looks like it would overcharge any device using it,
not just the RGB10 Max 3 — but I only have the two units above to test
on, so I've kept the fix scoped to what I can verify.

Thanks a lot for all the handheld DT work; none of these devices would
run mainline without it.

Juan Manuel Lopez Carrillo
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