OT -- laptop batteries (was Re: openoffice & xywrite?)

[Harmon Seaver hseaver@xxxxxxxx]

Carl Distefano wrote:
> Reply to note from "Robert Holmgren"  Sat, 11
> Aug 2007 23:47:25 -0400
>
> Robert:
>
>> I know for certain that in a wet cell, e.g. a golf cart or ATV-
>> type battery, if you let it drop below 50% you're just driving
>> a nail into its coffin (and those are very expensive batteries,
>> @ about $700/set). If you never let the charge go below 50%,
>> they will last maybe 6 years, otherwise you only get 1-2 years.
>> Are lithium batteries dramatically different?
>
> According to BatteryUniversity.com, lithium-ion batteries lose
> capacity over time whether they're used or not, but this "aging" can
> be retarded by storing the battery in a cool place with a 40% charge
> -- essentially supporting what you say. Supposedly lithium
> batteries have no "memory" (don't need to be discharged
> periodically, as nickel-cadmiums do), but I'm not sure I totally
> believe that. One thing is for certain, though (in my experience):
> overcharging them repeatedly is the kiss of death.
>
  Yes, the worst thing apparently is leaving them in the laptop when
you have it plugged in and are using the machine, so they stay hot. But
they do need to be totally discharged periodically, not all the time
like nicads, but once in awhile. One site said you should only discharge
them down to 30% normally, then fully discharge them every 10th cycle or
so.
  But many of the thinkpads seem to have a particularly bad time with
batteries and there are a number of sites devoted just to their
problems. The 600x (my latest) seems especially troubled, because of
it's own charging circuitry and the circuitry of the battery itself.

http://www.levien.com/tp600-battery.html
http://www.milnoc.com/TP600Battery/
http://www.thinkwiki.org/wiki/Maintenance#Battery_treatment
http://www.thinkwiki.org/wiki/Problem_with_ThinkPad_600_batteries

  I know that the lithium batteries in my heavy-duty cordless drill
seem to work quite well and have lasted a long time -- 3 years now --
with total discharges (for the most part) before recycling. I'm thinking
 that I'll treat the laptop battery the same way, and if it dies an
early death, replace it with NiMH cells, which are less problematic and
have a much longer total life, if not quite as good a run time as lithium.
  I'll be leaving this week for my cabin in northern MN where I'll have
no net access, and the only power comes from some solar panels charging
a bank of six 6v golf-cart batteries (lead-acid). Plus a gasoline fueled
generator to run power tools and recharge the batteries -- not enough
solar panels to meet the total need, although my lights are all LEDs and
halogens. The stereo uses a lot. Anyway, the lead-acid maintenance is
not all that simple either, they need to be equalized periodically and
given a higher "finish" charge to keep them up to snuff.




--
Harmon Seaver