Strange AC adaptor recognition problem on Panasonic Toughbook CF-71

I'm having a very strange problem with a Panasonic Toughbook CF-71
laptop that I have, and I'm wondering if anyone has ever seen anything
like it or has any insight.

A little while ago my AC adaptor went bad. It didn't die suddenly, but
rather seemed to slowly lose it's ability to charge/run the laptop for
extended periods of time. I verified this with a voltage/amperage
meter and found that the AC adaptor's voltage and/or amperage were
dropping or behaving erratically. Ordered a new adaptor, and it seems
to work fine.

But now there's a problem...

I think that laptop or the battery "adapted" to the lower voltage of
the old AC adaptor. The laptop now thinks the adaptor is plugged in
whenever the battery is inserted. It runs on the battery, but you get
the blinking red "battery confused" light. It will also run on the AC
adaptor, but the battery will not charge. To get the battery to
charge, you have to connect the AC adaptor, remove the battery, and
reinsert it. Sometimes you have to do this a few times.

I've tried messing with the battery to no avail. I cracked it open,
shorted the reset pin of the battery's charge indicator chip, and
drained the batteries 100% using a computer case fan as a load. (My
intent was to fully "reboot" the battery.) I then recharged the
battery and the problem persists. So my current guess is that the
laptop is the problem. The laptop has "learned" the voltage of the old
dying adaptor, and since that voltage was close to the voltage of the
battery it now can't tell the two apart. ... or at least that's my
hypothesis.

So does anyone know how I might reset the laptop's ACPI/power
management brains and get it to forget this information? Or, is there
some way I can recalibrate it? I know a bit about electronics, so I'm
comfortable hacking hardware.

Thanks.

-Adam

.

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