[svlug] question - my laptop won't charge to 100% even though plugged in and using AC power

Brian J. Tarricone bjt23 at cornell.edu
Mon May 4 01:23:36 PDT 2009


On Sun, 3 May 2009 22:52:03 -0700 Chris Miller wrote:

> On Sun, May 3, 2009 at 9:56 PM, Brian J. Tarricone

> > Nope, not in the least.  That may have been true of NiCad and
> > possibly NiMH batteries, but you'll get the exact opposite out of
> > Li ion batteries.  Repeated full discharges + full charges are also
> > what reduces their life.  Li ion batteries don't have the "memory"
> > that other types do that can sometimes be fixed by "refreshing"
> > them in this manner.  Doing full discharge/charge cycles will
> > actually make the battery worse.
> 
> I'd love to believe you, but personal experience with Li Ion batteries
> would suggest otherwise... Unless I'm getting stiffed and they're
> giving me NiCad while telling me it's Li Ion.

Then your personal experience must be a bit flawed ^_~.  Go and do some
reading on this.  Li-ion batteries have a limited number of charge
cycles.  Every time you fully discharge and recharge the battery, you
"use one up."  Fortunately only a full discharge/charge is considered a
full charge cycle, so, for example, draining the battery from 100% to
50%, charging it back up to 100%, and then repeating that, will only
"count" as one charge cycle.

> My old X40 actually had a battery "reconditioning" tool which would
> drain and recharge the battery (while it was still plugged in!) and
> I'm really certain that it used Li Ion batteries...

Mostly snake-oil.  Occasionally the circuit in the battery that keeps
track of the high and low charge water marks can get a little
confused.  "Reconditioning" in this case merely attempts to jog its
memory a bit.  You're only likely to get into this situation if you do
a lot of shallow discharge/recharge cycles, so most of the time you're
probably only reducing your battery's life (ever so slightly) by
performing this reconditioning.

	-brian




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