[NTLK] Recell Emate Batteries

[NewtonTalk]

> This holder have almost perfect dimensions. So, we only need 4x NiMH
> batteries to put inside, mount thermistor somewhere between NiMH
batteries,
> and solder ?positive? and ?negative? cables to pins on original white
connector.
> Piece of cake.

Please allow me to disagree with all due respect...

If this was a piece of cake, I'd have offered this as an alternative to
battery rebuilds years ago. The reason why I've never offered this yet is
the unfortunate fact that I've never found a holder that'll fit into the
eMate's battery compartment and can still handle a current of 1.2 Amps for
longer than a couple of seconds.

A couple of years ago I thought I had found such a holder. But I was unable
to get a datasheet for it. I exchanged several E-Mails with the
manufacturer, and they said that "it would probably work". But they
couldn't, or wouldn't, send me a legally binding datasheet. But they kindly
sent me two samples. It took about four minutes until the first of the two
started to smell and smoke. In your case, it might not be so obvious. It
might take longer and depend on the ambient temperature. But I'd rather not
leave an eMate alone while it is charging unless what I describe above is
ruled out.

If you do find a holder that has a specified current of 1.2 Amps or more,
and if you have the datasheet and a written confirmation from the
manufacturer, it'd be cool if you let us know. Not that that'd be enough,
though. After all, the battery contacts must also withstand 1.2 Amps forever
without getting overly warm. Battery contacts have a tendency to deteriorate
over time. Which will increase the contact resistance, resulting in higher
contact temperature and even more deterioration. That's why Apple
spot-welded their packs. Not spot-welding them would have been much cheaper.

That  being said, let me shed some light on your pack's two components.
You'll need the thermistor (that's the component with the two white wires),
otherwise the eMate will not charge the pack. You don't necessarily need the
thingie with the yellow sticker. The pack will also work if you replace it
with a piece of wire. Just as you'll most likely reach your destination in
one piece although you weren't using your seat belt. Unless, of course,
something happens during your trip that makes you wish you had used it after
all. It's about the same situation with this component. Do you normally
buckle up?

This component reduces the current if you accidentally short the pack's
contacts out. For many, many years I had thought that this couldn't possibly
happen, given the way a 2x00 pack is built. And then
She-who-must-not-be-contradicted threw a pile of tools I had left on my
living room table right on a freshly rebuilt 2x00 pack on my workbench
because we were expecting guests and she rightfully thought that a dinner
among well-used screwdrivers, glue cartridges and pliers might not be such a
good idea. I noticed that about ten minutes later when I put the tools where
they belong and was surprised that the pack was so warm. Hadn't Apple put
that little component in, I might no longer have a house.

Cheers

Frank

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