[NTLK] Make OMP / MP100 charge cells in a standard battery tray

[Frank Gruendel]

This answers several posts to save bandwidth...

>> "... it is very easy to convert a standard alkaline battery holder

> I'd be grateful for thoughts on how to accomplish this. 

Please see below.

> Having recelled an eMate battery pack, I am familiar with the 
> gizmos (technical term) used in that unit to prevent 
> overheating. Are similar sensors a necessary part of 
> converting the OMP battery tray to a rechargeable unit?

No, they aren't.

> What sort of rechargeable cells would be recommended?

Nickel-Cadmium AAA size cells with soldering tabs. Do NOT use NiMH type
cells.

> The 1x0 will charge the NiCd batteries by simply binding the 
> two inner cells together with a piece of cello tape.

This is true for the MP110, MP120 and MP130. The battery pack of the MP100
and OMP is different.

> The Notepad/OMP/H1000 used NiCd batteries as well. NiCd cells 
> use a different charging regime. They are charged more slowly 
> and the end of charge is detected by a final dip in the cell 
> voltage. 
> Therefore the OMP has no need for a temperature sensor for 
> charging (it has one for auto-contrast adjustment).

I beg to differ. It does have need for a temperature sensor, and it does in
fact have one. The sensor is not part of the battery pack, but located in
the Newton't battery compartment. This applies to all Newtons older than a
2x00. I wish they had stuck to this when they developed the 2x00.

To answer your initial question: The OMP and MP100 can sense the difference
between a rechargeable battery pack and the standard battery cell holder
because the recargeable pack, when inserted, presses a switch inside the
Newton. You can trick the Newton into believing that the batteries are
rechargeable by screwing a little screw into the battery holder that presses
this switch. You should be aware, however, that you will be tempting fate if
you do this, because you cannot rule out that someone will put cells other
than NiCad rechargeables into this holder. The Newton will happily try to
charge whatever you put into the battery holder, and this might lead to
results that you don't want to be close to when they occur. When I rebuild
OMP battery packs, I put heat shrink tubing around them that will prevent
removal of the cells, and just to be on the safe side, I put a warning
sticker on the heat shrink tubing...

Frank

-- Newton software and hardware at http://www.pda-soft.de