[NTLK] MP 2100 Battery reconditioning

From: Thomas Hofts (thofts_at_mac.com)
Date: Tue May 14 2002 - 16:14:25 EDT


I know this subject has been discussed to death.

My 2100 with the rechargeable NiMh battery I got from Philly Discounter's
suffers from the "10 min. charge time - 4 hour continuous use life (using
back light)" problem. I tried the "let it run out completely and recharge"
solution a couple of times, but still had the 10 min. charge time.
Monitoring the battery via Lava during the charge I saw a rapid rise in
battery temperature which coincided with the percentage of charge in the
battery. So I decided to conduct an experiment theorizing the rise in
temperature was preventing erroneously showing the battery receiving a full
charge.

1. I placed the battery in my freezer and cooled it to 32 F, wiped it to
remove any condensation, then placed it back in my 2100 which was powered up
with the AC adapter. I then immediately unplugged the AC and to my surprise
the "discharged" battery continued to power the 2100 with back light on for
8 minutes, finally dying when it dipped below 10%.

2. I then rebooted the Newton with the AC. The monitor showed the battery
taking a "trickle charge" for 9 min. until the battery temperature reached
41 F. Then it went into fast charge mode. The battery temperature gradually
rose until it reached the ambient temperature 37 minutes later (82%
charged).

3. I placed a small icepack wrapped in cloth at the very end of the Newton
(not on top of it) to help keep the battery temperature cool. This kept the
battery 3 degrees cooler than the ambient temperature. The battery continued
to fast charge and reached 100% and trickle charge 16 minutes later.

Total charge time was 53 minutes. I then allowed the trickle charge to
continue for another hour.

Disconnecting the AC, I left the 2100 on, with the back light on, and it ran
for 11 hours 22 min. before shutting down.

I then recharged without cooling the battery and the total charge time to
100% was 48 min.

Seemed to work, at least for the short term.

Any comments?? (Outside of the fact that I have too much time on my hands!)

--
Tom Hofts

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