Re: [PATCH v3 2/3] power: supply: Add bd718(15/28/78) charger driver

Andreas Kemnade
2025-08-29T11:15:50Z

Am Fri, 29 Aug 2025 09:35:00 +0300
schrieb Matti Vaittinen <mazziesaccount@gmail.com>:

> > to indicate that a measurement of the open circuit voltage
> > is available in some register, which enables you do do more
> > precise capacity estimation, right?
>
> AFAIR, the ROHM fuel-gauge algorithm used OCV tables when battery was
> not really open, but 'relaxed', to adjust the coulomb counter based on
> the SOC estimated from the OCV. The 'relaxed' condition was met when the
> current consumption had been 'small', and battery had not been charged
> 'recently'. I have a vague memory the BD71828 had some hardware support
> for knowing battery was 'relaxed', the BD71815 and BD71827 might have
> used coulomb counter 'history' for this. I can try to remember all this
> a bit better if Andreas continues to upstream also the fuel-gauging
> logic from the original RFC. But yeah, these interrupts were for over
> current.

78 at least has. But then the question is how often the relaxed state
really is reached. Current limit is around 3mA per default
(REX_CURCD_TH). So if your
power management is suboptimal, you will not reach that state on
discharing. So, regarding charging, at least when I am on vacation,
the limit on available energy is also my protection against spending
too much time with my electronics (esp. on the smartphone). But that
also means that I will not always charge the device fully. Lowering
current may also mis-indicated that the battery is full.
So the scene is set for any mess with fuel gauges, not limited to the
BD71878.

Regards,
Andreas