Re: [PATCH 3/3] thinkpad_acpi: document the battery controls

["Ognjen Galić" <smclt30p-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Mon, May 14, 2018 at 09:03:02AM -0300, Henrique de Moraes Holschuh wrote:
> On Sun, 13 May 2018, Ognjen Galic wrote:
> > +Battery force discharging
> > +--------------------------
> > +
> > +There is also support for AC overriding. This means that you can force the battery to discharge
> > +even when AC is attached. This is also exposed via the generic ACPI driver:
> > +
> > +/sys/class/power_supply/BATx/force_discharge [int, 1, 0]
> > +
> > +Setting it to 1 forces the battery to discharge on AC.
> 
> This is used to run a battery "fuel gauge" callibration cycle.
> 
> One has to set the limits to 0,100 (i.e. disable the anti-wear
> limiters), trigger a force_discharge, and wait until it discharges to
> zero.  At that point, the EC is supposed to reset the force_discharge
> bit by itself, and then you have to wait the battery to charge back to
> full.

That's the intended use case for this patches via an upcoming program I
am writing for userspace.

> 
> (and at least on older thinkpads, where you had to use SMAPI to do the
> above, it didn't need much help from the operating system.  Once a
> couple years you could just set force_discharge on both batteries (with
> the thing connected to AC), shutdown the operating system, and go to
> sleep.  By morning, it would be fully charged and both gauges
> calibrated, still powered off, ready to go :P ).
> 
> -- 
>   Henrique Holschuh

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