[NTLK] MessagePad 2100 recell problem
anasazi4st at me.com
Fri Aug 6 06:14:01 EDT 2010
On Aug 05, 2010, at 09:35 PM, Gavin Watson <gavin83209 at gmail.com> wrote:
I'm really stumped here. Does anybody have any other ideas? Thanks in
First off--have you read Frank Gruendel's excellent article on recelling the Newton Ni-Cad battery pack? It can be found here: http://www.pda-soft.de/mp2k_battery_pack.html .
I'm no expert on this (that would be Frank)...but that hasn't stopped me from successfully recelling four Ni-Cad Newton MessagePad battery packs. All work perfectly...although there is a "learning curve" to getting it right.
The first one, no problems...in a few hours I had it done. The second attempt I breezed through, thinking I had the procedure down pat--I didn't, and I ruined the plastic casing and the small metal connecting strap on the inside bottom. I took much greater care with each of the next three. Here's some things I've learned, based on my experiences. These are in no way set in stone, so to speak...but they've worked well for me.
1. I buy my batteries here in the US at a store called Fry's Electronics. They're big in California, but there's also stores in Arizona and Texas, and I'm sure several other states. They're primarily in the Western US...they have a website called, oddly enough, www.frys.com. They're certainly not the only source by far...but I can walk in there and walk out with what I want, after looking at about a dozen different offerings by several companies, most well known (avoid the Vivitar batteries, though!).
You should be getting something in the 2000-2600 mA range. In most cases cost doesn't play a big part in which you choose within that range...Eveready, Sony, Ray-O-Vac are all good proven choices, and run from about $12 USD to more than $20 USD.
I don't follow Frank's instructions on side-tab batteries...although I'd bet that if I *did* try them I'd be hooked...Fry's doesn't sell anything like that, so...it's a question of convenience.
2. I also don't try to put the "lid" back on. It just seems too much trouble, and I don't see the point. Having my cells visible means I can watch for corrosion, etc., and they work just fine that way. For me, there's too much sanding and reshaping to reattach the lid and have it fit properly.
3. I solder a short length (2 inches) of 16 gauge single-strand copper wire to the side of the tip on the positive side of one battery...and a similar piece to the negative side as close to the outer edge as possible to another. If done properly this length of wire can be looped around in a circle between the negative end and positive end of one set of 2 cells (and the positive-negative ends of the other set) with no ill effects. REMEMBER that these cells are somewhat sensitive to heat, so solder as quickly as you can, and when they start to get warm stop and let them cool down for a bit.
4. The thermistor is VERY important, and I would bet that's part of--if not all--of your trouble. If it's not possible to salvage the one you had originally, you'll have to find another pack and cannibalize its thermistor. ALSO VERY IMPORTANT is the small strap with the yellow sticker and numbers on the bottom of the pack that connects the negative and positive ends of the two cell "pairs". It's been my experience that without it the pack just won't function properly. I *can* tell you that you don't need a lot of material left of the original piece there to have it work okay..but it does have to be there.
5. Frank says that you should test the pack when completed by first checking DC voltage from the silver contact disk (negative) to the right side contact (positive)...it should be 5-6 volts (assuming the cells were pre-charged--almost all are). Check how well the thermistor works with the two contacts on the obverse side --10 kiloOhms is good, but the temperature can cause this to vary widely. Any other wider variance in any of these numbers and there's something wrong/not connected properly.
I hope this is a help or at least a step in the right direction.
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