# [NTLK] Testing Battery Capacity on MP2x00

From: Frank Gruendel (Frank_Gruendel_at_t-online.de)
Date: Sat Jun 08 2002 - 16:56:18 EDT

> there are a lot of "intelligent" charge processors on the market.
> This would be the best way to determine the battery capacity and to apply
> several treatments like normal charge, fast charge and controlled
discharge
> to the batteries.

This would only make sense if it was done to the cells seperately. Which
you can do on a 110/120/130, but not on an OMP/100/2x00/eMate.

> The only problem is to interface the Newt battery pack to the charger.
> But this is solveable I think.

If all you want is the capacity, there's an easier way (assuming the four
cells are in pretty much the same condition. If they aren't, forget it).

1) Get yourself four 10 ohms resistors and a voltmeter.

2) Connect the resistors like that:

A o---XXX---XXX---XXX---XXX---o B

2) Fully charge the pack in the Newton.

3) Remove the pack.

4) Connect A to the round contact (-) and B to the
rectangular contact at the side where only one
rectangular contact is. Write down the start
time.

5) Monitor the voltage across A and B until it
reaches 4.0 volts.
This will take about 10 hours for a new original pack
or about 14 hours for one I refurbished.

6) Remove the resistors.

7) Write down the elapsed time.

The formula to calculate the capacity is

Capacity = 120 mA * elapsed time (in hours)

Caution: It is mandatory that you stop the discharge as soon as the
pack's voltage reaches 4.0 volts. If you forget this, the pack will be
deep-discharged which is for a couple of reasons not a good thing
(I know some of you disagree here, but I'm not going to change
my mind).

Note: If you manage to get a 1 Watt 40 ohms resistor, you needn't
get the four I described above. But those are kind of hard to come
by. 10 Ohms can be obtained pretty much everywhere, moreover,
if you do it that way you could use a 0.25 Watt type which is quite
cheap.

Frank

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

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