[rescue] iBasketcase

Phil Stracchino alaric at metrocast.net
Tue Jan 22 05:28:01 CST 2008

Charles Monett wrote:
> Curtis H. Wilbar Jr. wrote:
>> TP600 had a battery charging issue ?  TP600E or TP600X ?  I have a TP600X
>> that the battery no longer charges...  so curious as to what you are 
>> referring to.
>> -- Curt
> http://www.thinkwiki.org/wiki/Problem_with_ThinkPad_600_batteries
> It was related mostly to the smart monitoring of the batteries and some 
> part due to the charging patterns they got - where there would be a 
> sharp drop-off reported with the batteries even after a relatively short 
> time of use (short as 3 months).

Basically the problem was that IBM tried to use a single charge control 
chip per pair of cells instead of a charge control chip per cell, to 
save money.  The way they did it, it was possible for the cells to drift 
relative to each other.  The "full charge" and "full discharge" levels 
on a lithium-ion cell are about half a volt apart.  So if one pair of 
cells drifted (perhaps one cell had higher internal resistance than the 
other), the battery would read discharged when the low cell of the pair 
reached the low limit, and read full charge (and stop charging) when the 
high cell reached the high limit.  If any two cells in the battery ever 
drifted half a volt apart, the entire battery became a brick, even 
though all the individual cells were actually still good.

I understand people have managed to resurrect Thinkpad 600 batteries by 
disassembling the battery and individually charging the cells.

   Phil Stracchino, CDK#2         ICBM: 43.5607, -71.355
   Renaissance Man, Unix ronin, Perl hacker, Free Stater
   alaric at caerllewys.net            alaric at metrocast.net
           It's not the years, it's the mileage.

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