Re: [PATCH 00/10] Add RT5033 charger device driver

[Pavel Machek <pavel@ucw.cz>]

Hi!

> Some comments on the end-of-charge behavior. The rt5033 chip offers three
> options. In the Android driver, a forth option was implemented.

Hmm. I'm working on that on motorola-cpcap driver, and I guess this is going
to be common problem for many drivers.

> - By default, the rt5033 chip charges indefinitely. The current goes down but
>   there is always a charge voltage to the battery, which might not be too good
>   for the battery lifetime.
> - There is the possibility to enable a fast charge timer. The timer can be
>   set to 4, 6, 8... 16 hours. After that time has elapsed, charging stops
>   and the battery gets discharged. This option with a timer of 4 hours was
>   chosen by Beomho Seo in the patchset of March 2015. However, that option
>   is confusing to the user. It doesn't initiate a re-charge cycle. So when
>   keeping plugged in the device over night, I find it discharging on the
>   next morning.
> - The third option of the rt5033 chip is enabling charging termination. This
>   also enables a re-charge cycle. When the charging current sinks below the
>   end-of-charge current, the chip stops charging. The sysfs state changes to
>   "not charging". When the voltage gets 0.1 V below the end-of-charge constant
>   voltage, re-charging starts. Then again, when charging current sinks below
>   the end-of-charge current, the chip stops charging. And so on, going up and
>   down in re-charge cycles. In case the power consumption is high (e.g. tuning
>   on the display of the mobile device), the current goes into an equilibrium.
>   The downside of this charging termination option: When reaching the end-of-
>   charge current, the capacity might not have reached 100 % yet. The capacity
>   to reach probably depends on power consumption and battery wear. On my mobile
>   device, capacity reaches 98 %, drops to 96 % until re-charging kicks in,
>   climbs to 98 %, drops to 96 %, and so on. Not reaching 100 % is a bit
>   confusing to the user, too.

Is the system powered from the battery in the not-charging case?

Anyway, we should teach userspace that "full battery" does not neccessary mean 100%,
as keeping battery at 4.3V wears it down quickly.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
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