XO battery/performance [Devel Digest, Vol 76, Issue 21]

Richard A. Smith richard at laptop.org
Sat Jul 21 05:52:45 EDT 2012

On 07/21/2012 03:05 AM, Yioryos Asprobounitis wrote:

>>>> - ok bg-acr@ .bg-acr (Should print zero)
> ACR: -0.42

Hmm... I was expecting zero.  I'm traveling to Taiwan right now and
don't have 1.0 or 1.5 with me to check.

>> - Insert battery
>>>> - ok bg-acr@ .bg-acr
> ACR: -0.84

.42mAh / 24 hours = 17.5uA so very low.  Does not appear to be a
hardware fault in the battery.

> - ok batman-stop - Poweroff - Remove AC - 25 h battery IN the XO -
> remove battery - Plug AC - Boot XO and stop at OFW - ok batman-start
> - Insert battery - ok bg-acr@ .bg-acr
> ACR -469.52

Assuming -.84mAh was where you started thats
468.68 mAh / 25h = 18.7mA which is just about what olpc-pwr-log
indicated was happening.

This really smells like the EC not going to sleep although I thought we
proved it was going to sleep with an earlier test.  (Low battery LED
going out when you power off)

Please dump the registers and EEPROM (bat-dump-banks) again and I'll
program them into a battery and test it on a XO-1.  No rush though I
won't be able to do anything with this for at least 2 weeks when I back 
in Boston and working.

Perhaps I'll think of some other thing to look at between now and then.

> -insert battery - ok bg-acr@ .bg-acr (no batman.fth/batman-start)

commands like bg-acr@ require batman-start to work correctly.  If
batman-start has not been called then they will call it for you.  We
call it explicitly so that the charging system is disabled prior to
inserting the battery.

> Booted up with battery, plugged AC,  power LED stays red.

This is an invalid condition.  With AC connected you should either have:

Blinking red: Error
yellow (some say orange): Charging
Green: Full

If its not one of the above then either the EC charging system is 
disabled in which case the LED values are somewhat random or your power 
adapter is not providing power.

> Booted without battery, inserted battery, battery shows empty and
> charging. Charged to about 15% slowly, then jumped to 81% and then
> 97% in under 1 min and the power LED turned green!
> Now, you are going to say again that I do not know what I'm doing,
> but sure none of these looks very normal behavior to me and may have
> to do with how the battery "communicates" its state than its state
> per se.

Yes and I'll continue to say it as long as you continue to do things
that are invalid and will produce nonsensical results.  I've told you a
few times that when you run commands like bg-acr! that you are modifying
important values outside of the EC and that until you do a full
discharge/recharge cycle normal reporting won't yield valid results.

The jumps are when the EC detects specific conditions and tries to reset
the SOC accordingly. Normal and expected.

If you want to understand whats going on the please run olpc-pwr-log so
you can observe the voltage and current and see when the EC changes
things based on those values.

Richard A. Smith  <richard at laptop.org>
One Laptop per Child

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