New joyride build 2506 - q2e19

Richard A. Smith richard at laptop.org
Sun Oct 5 19:15:29 EDT 2008


Mitch Bradley wrote:
> rihoward1 at gmail.com wrote:
>> Another strange thing I see with q2e19 is that at 19% battery, 
>> according to the battery gauge, the battery indicatory lamp started 
>> flashing red and orange.
> 
> That would be a function of the EC code.  Richard, any thoughts?
> 

Yes.  That is one of the 3 new EC features in this release.  I had to 
leave for my weekend before I could do proper changelog docs on the wiki.

Alternating red/yellow battery LED is the critical voltage level 
warning.  It means that your battery voltage has dipped to where its 
crossed the 5.7V threshold.  It means that you are into the very 
non-linear voltage discharge curve.    If it reaches 5.35V the EC powers 
off the voltage regulators for the rest of the system.

5.7V is a bit of a guess on my part.  I tried to make it close enough to 
the hard shutoff that its meaningful yet far enough out so that there's 
enough time to do something even on batteries where the curve rolloff is 
very steep.

This should normally appear when the battery is less than 10%.  The hard 
shutoff occurs somewhere in the 4%-7% zone. [1]

It should not have occurred at 19%.  So one of 2 things happened:

1) EC Code bug.
2) Your SOC % reading does not reflect the actual state of the battery.

Item 2 can occur 2 ways:

1) It sat on the shelf or in an XO turned off for a long time (ie weeks)
2) You have the charge balance problem in your cells.

olpc-pwr-log will tell you which of the above is at fault. My bet would 
be its an early warning sign of 2.2 which is good since thats exactly 
one of the things this is supposed to try and detect.

To test:

Run your battery down until the EC shuts you off
remove battery.
Power up the XO without the battery
once booted run olpc-pwr-log in a VT or disable idle-suspend
Insert the battery
Charge until full
Ctrl-C
restart olpc-pwr-log
After you see the first line of log output pull the power cable
Let it run till the EC shuts you off.

Then look at the 2nd log file (the discharge cycle). The very last 
columns of numbers should end up in the -2800 to -3100 range.  If not 
then your battery is suspect.  Send me the 2 log files regardless 
because I want to review them.

There's also some info here:

http://wiki.laptop.org/go/XO_LiFePO4_Recovery_Procedure

But if you really are only off by 10-13% then it maybe hard to tell 
looking at the charging log as described in that procedure.  The log 
analysis on the wiki is for the most common charge balance failure symptoms.

[1] The SOC % reported up to the host is based on the typical raw 
capacity of the battery not the usable capacity which is why the numbers 
for fully charged and empty are weird.  Scaling this % so that its a 
sane 0% - 100% is on my list of changes for 9.1

-- 
Richard Smith  <richard at laptop.org>
One Laptop Per Child


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