NTLK Newton Battery Charging - Excessive Heat Explained

From: DrNewton (DrNewton@kc.net)
Date: Tue Jan 25 2000 - 00:58:50 EST

In NewtonTalk # 225, Keith Isley was quoted :

>I've noticed that sometimes my Newt 130 gets really warm when it's sitting
>on the charging base. It worries me, because I know heat is not good for
>computers in general - and probably even worse for the Newt, since
>everything's enclosed in a small space.

When recharging the rechargeable packs in the Newton ( any model ), they use
a thermistor to sense the "burst of heat" when the cells get "topped off".
This high temperature spike is monitored along with the charging voltage and
used to control the charging current. If the charging / pack voltage is at a
certain point AND the temperature spikes, the charging circuit is switched
to a lower "trickle charge" current. The temperature of the pack / Newton
should drop down after several minutes to "warm"

Note that I used the word AND above. If a cell is partially shorted, the
charging circuit gets loaded down. Charging continues.

If your pack has a partially shorted cell, the entire pack can get VERY HOT
due to the fact that the non shorted cells are getting over charged. This is
not a good thing !

I have seen units where the hot packs have melted the battery compartment
plastic !

If you have any doubt about your cells, check them with a volt meter. The
individual cells in the 110/120/130 pack should measure at least 1.0 volt.
The combined cells in the pack for the MP2x00 should measure 4.0 volts at

Hope this helps.

Best Regards,
David Watson

A.K.A. "Dr. Newton", "Digital Ocean Dave"
Kansas City, Missouri
Provider of the MP2000 Upgrade and certain repairs.

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