[NTLK] Update on 2100 NiMh Battery "freezer"reconditioning

From: Thomas Hofts (thofts_at_mac.com)
Date: Thu Jun 06 2002 - 18:08:22 EDT

After 2 weeks and 4 normal recharges I am still getting 45-55 min recharge
times and a whole lot more life out of my rechargeable NiMh battery.
Below is my first post.

Tom Hofts


Visit my homepage at:


> 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 Dashboard 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 > 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.

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