[NTLK] MessagePad 2100 recell problem

[Gavin Watson]

On Aug 6, 2010, at 3:14 AM, Forrest Buffenmyer wrote:

> 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 have read that, actually.  Good stuff.

> 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!).
Fry's is a good store.  I have one a bit under an hour away from where  
I live, though I mostly buy specialized batteries like this online in  
bulk, if possible.  These particular batteries are actually from  
Walmart, though.  I've rebuilt a few battery packs for other devices  
in the past and I'm impatient with shipping, so I just got some  
precharged Rayovacs without tabs, as I said previously.

> 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.
Mine are rated at 2100 mAh for $9.97.  I used the same things in my  
MessagePad 110 a while ago with success.

> 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.
Well, I am somewhat embarrassed to say that I misidentified the  
thermistor in my previous email.  By thermistor, I meant the little  
yellow square.  It has been reattached with a few strands of what used  
to be twisted copper wire and electrical tape as a temporary measure,  
but it still doesn't seem to be working quite right.  I also seem to  
have somehow misinterpreted a bit of the wiring in the process.  The  
thermistor seems to output voltage at least.  I don't currently have  
access to a working multimeter (mine seems to be dying), but I should  
tomorrow.  I'll test it then.

> 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.
The wiring all looks fine to me, though it hasn't been properly  
tested.  I reattached the positive thermistor contact on the logic  
board again (it's not going anywhere this time!), but it still doesn't  
appear to work.  I'll keep these voltages in mind when I run a proper  
test.

> I hope this is a help or at least a step in the right direction.
Very much so.  Thank you sincerely.  It has been an enormous help.