Battery recovery issues

Richard A. Smith richard at
Tue May 5 17:44:15 EDT 2009

Emiliano Pastorino wrote:

> bat-charge reports this: 320.83 mAh (7d53) 1428.12 mA (2ddc) 6.492 V
> (195c) Chg: 0.41mAh (  29) then every column raises line to line (I
> copied that by hand because

> bat-charge-log always says "Can't open file", even when usb stick is 
> plugged in.

Turns out the way I did the disk devices won't work unless you either:

1) boot with a usb drive plugged in
2) run 'p2' before bat-debug-log

'p2' will re-probe usb devices.

> If the first column is battery's charge, then it's almost dry. Should
> I try bat-recover or charge it the usual way?

The first column is the ACR reading and you can't tell anything by just
1 reading.  You have to know what it was when you started discharging or
charging.  I don't report SOC in that listing cause generally I don't 
care.  I want to know what it does after I turn on charge rather than 
what level it was at previously.

bat-charge simply enables charging and then starts reading the battery 
directly.  Thus it does not care about any of the settings in the 
EEPROM.  Its a good diag tool to see if the battery just physically 
won't take charge or if you just can't communicate to it at all.  If 
bat-charge works but normal charging does not then its EC or EEPROM 
badness.  The LFP batteries have an overvoltage cutoff that will protect 
them so its ok to just turn one on and leave it.  For NiMH you would end 
up reducing its life.  But since you don't have any NiMH you don't care.

'bat-recover' works by PWMing the charge pin to keep the charge current 
very low and allow the cells to equalize yet not trip the over voltage 
like they would if you just turned on the charge and left it.  The 
settings I've picked by default seem to work in most cases but I've had 
many batteries where I needed to reduce the current even further from 
the default settings.

To speed up the process you can use normal charging methods to get the 
battery close to full (or wherever it cuts out at)  That way the recover 
process will be much shorter.

> I'll try bat-recover with a bunch of batteries today, so maybe
> tomorrow or on Wednesday I'll be sending you some logs, if it is ok
> to you.

After looking at your bat-debug log I've realize that the extra 
diagnostic info is only present in f-series firmwares with my newer EC code.

I'm forwarding you an e-mail with a copy of q2f02 that I worked on while 
trying to solve some problems with batteries in another deployment.

q2f02 will be behind q2e41 in terms of OFW but has EC code with extra 
battery diag info.  For battery testing there should no difference 
between the 2.

Its also available here: (Just never announced since a new e-series 
release happened right after)

So install f02 on your test laptop and re-run bat-debug-log after you 
have first run 'p2' and the logging to disk should work.  I don't need 
any more see-bstate info.

so the steps:

install f02
remove battery
stop at ok
insert usb drive (or boot with it inserted)
run 'p2'
run 'bat-debug-log'
insert battery
run for a couple of minutes then hit a key
send me the log.

I'll try to get a f03 out soon with the latest of everything but I've 
got gen 1.5 bring up tasks that I need to attend to.

Richard Smith  <richard at>
One Laptop Per Child

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