Re: [NTLK] eMate pack charging problem

From: Frank Gruendel (fg2_at_pda-soft.de)
Date: Fri Oct 03 2003 - 13:36:13 PDT


> Type:Apple NiMH rechargeable pack
> Voltage: 4.5 Volt
> Capacity: 15%
> Low Warning at: 20%
> Auto Shutoff at: 0%
> AC Adapter: connected
> Charge State: discharging
> AC Voltage: 7.34 Volt
> Discharge Current: 0.001 Ampere (This fluctuates 0.001 and 0.000)
> Inside Temperature: 22.42 Celsius
> Cell Temperature: 64.00 Celsius

Ok, here's an attempt at interpreting these values...

1) Good that I wrote NewtTest ;-)

2) If it says NiMH rechargeable pack, it has recognized that
the pack is rechargeable

3) Reporting 15% capacity at a voltage of 4.5 Volt is normal

4) It sees the ac adapter and the ac voltage is ok.

5) It shouldn't say "discharging", though. Obviously it doesn't
charge (which was your problem in the first place).

The reason for this is the cell temperature. There is a little
temperature switch inside the Newton that will (nearly) open at that
temperature, that way it is ensured that the remaining current
won't explode the pack in case the eMate's charge circuitry runs
amok or the pack is shorted.

Now there can be two reasons for such a high temperature.

a) The Newton only thinks the temperature is that high because
the refurbisher either installed a wrong temperature resistor
or fu**ed up putting in the old one back again.

b) The temperature is really that high. You should be able to
find that out easily by touching the pack while this temperature
is reported. If it is extremely hot, the eMate is probably right.

If it is in fact hot, I would think that one of the cells is dead.
4.5 Volt would mean 1.125 Volt per healthy cell which is nearly the
discharge
voltage. If that was the case the cells would charge just fine and
not become overly hot.
If, however, one cell has a short, 4.5 Volt would mean 1.5 Volt for
each of the remaining three cells which is perfectly possible for
cells that are currently being overcharged. In that case the three
cells would, since they can't take in additional charge, simply
convert the current into heat.

Frank

-- Newton Software and Hardware at http://www.pda-soft.de

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