[Power] Checking the life battery of XOs batteries deployed after 3 years of usage

[Richard Smith]

On Wed, May 15, 2013 at 10:15 AM, Xavier Carcelle
<xavier.carcelle at gmail.com> wrote:
> Dear power OLPC folks,
>
> As we work on the NosyKomba, Madagascar team of OLPC France, we are
> keeping on expertizing the states of the 200+ xos we deployed there
> and we are wondering if we can estimate the life duration of the
> batteries we have for the XOs after 3+ years of usage there.
>
> The only simple solution we see if logging the "forth" test of the battery :
> ok Testing /battery at 0
> AC:off Battery: BYD LiFePO4  68% 6.46V -0.60A 34C discharging Okay
>
> Is there any way of plugging an equipment to check the battery life
> and check their states ?

Yes. I have a tool for doing exatly that.  Actually I have 2 tools but
the 2nd tool which is used at the factory is designed for a 1.75 or
XO-4.  I've made it run on the 1.5 but it needs some firmware mods.
Its not much different than what I'm describing below.

The tool that works on all laptops however is called olpc-pwr-log.  It
has been in the OS build since XO-1 days.  So its guaranteed to be
there.  However, you may want to get the latest copy for doing tests.
The most recent copy can be found here:

http://dev.laptop.org/~rsmith/pwr_scripts/olpc-pwr-log

Basically what this does is just log the data from the battery.
Information on the output and usage is here:

http://wiki.laptop.org/go/XO_power_draw#olpc-pwr-log

Basically to measure capacity you would:

1) Charge up the laptop.
2) Disable auto power management (if enabled)
3) run olpc-pwr-log from a terminal
4) disconnect external power
5) let the laptop sit until it powers off.

Then power the laptop back up and look at the logfile that
olpc-pwr-log created.  If you are using a new version of the script
then the 8th column is your net capacity in mAh.  Newer scripts have 9
columns and the 9th is net time in minutes.

I'm very interested in your data.  Please send me copies of all the
log files you generate.  I'd like to see what a 3 year usage looks
like as well.

I have python tool(s) for processing files in build or for looking at
various things.  Let me know if you want to learn how to use them.
Net mAh however should give you a good indication of your current
capacity.

2800mAh is the number I use for capacity of a new battery on its first
cycle.  Some batteries can be higher but all batteries should start
out at at least 2800mAh.

--
Richard A. Smith
One Laptop per Child