[TriLUG] Thinkpad Battery Charging Thresholds
Joseph Mack NA3T
jmack at wm7d.net
Sun Feb 20 09:25:48 EST 2011
On Tue, 15 Feb 2011, Joel James Adamson wrote:
> After a while of just unplugging when I got near 80 %, the battery
> remarkably stopped charging by itself. I mean that I could plug it in
> and if it were below 30 %, it would charge up to near 80 % (79.7 % IIRC)
> and stop charging. Also, if it was above 30 %, I could plug it in and
> it wouldn't charge at all, but then if it dipped below 30 %, it would
> charge as described above. Problem solved, right?
> I know that .. get to it through Thinkvantage in Windows.
>  http://www.thinkwiki.org/wiki/Tp_smapi
This sent me off on some exploration. To confirm Joel's
Fig 2 of
shows that if the cell voltage is 4.2V or less, the battery
life is greatly extended, presumably past when you'll want
to chuck the laptop.
Table 2 of
shows that 4.2V corresponds to 85% charge. Using
Thinkvantage under Windows (dual boot), I set the battery to
not start charging till the battery is below 50% and to stop
charging at 80%. Here's my laptop going through two
At 19:30 I unplug the charger. At 20:10, after the battery
drops below 50%, I plug in the charger and the battery
charges to 80% and stops charging.
At 00:00 through 02:15 I unplug and replug the charger
several times. Untill the battery drops below 50%, plugging
in the charger only takes over powering the laptop, but
doesn't charge the battery (battery charge doesn't change).
At 02:15 the battery has dropped to 45% and plugging in the
charger recharges the battery to 80% again.
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at http://www.wm7d.net/azproj.shtml
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