old battery?

[Derek Broughton]

Eberhard Roloff wrote:

> Derek Broughton wrote:
> 
>> Paul Kaplan wrote:
>> 
>>> As I suspected...
>>> design capacity:       47520 mWh
>>> last full capacity:      14910 mWh
>>> 
>>> Will cycling the battery from full to discharge 2-3 times restore the
>>> ability
>>> to charge to design capacity?  Is there anything else I might try or am
>>> i destined for a replacement?
>> 
>> Don't even think of doing that.  My LIon battery was in much the state
>> yours
>> is in December.  Then it accidentally fully discharged (I put my laptop
>> in
>> its bag before making sure it had successfully hibernated).  It went from
>> a
>> 45 minute charge to a 15 minute charge.  LIon batteries should NEVER be
>> allowed to go completely flat.
>> 
> My experience is slightly different.;-)
> 
> Using a Thinkpad, I usually follow the procedures outlined here:
> http://www.thinkwiki.org/wiki/Maintenance

Apparently you don't follow the advice very closely.  The very first thing
it says about LIon batteries is "avoid deep discharges except when
resetting fuel gague or reconditioning a battery; partial dis-/recharges
are better for the battery lifetime (note: fuel gauge will slowly get
inaccurate over time)".

Yes, a deep discharge/full recharge will recalibrate the fuel gauge, but it
_still_ doesn't do anything good for your battery life.  Cycling the way
Paul suggested will ensure that the fuel guage is accurate, but his "last
full capacity" is likely to be even smaller.

fwiw, I'm not convinced that the guage gets inaccurate over time, either.
-- 
derek