PSN-L Email List Message

Subject: Split/tapped batteries not recommended
From: "Charles R. Patton" charles.r.patton@........
Date: Tue, 08 May 2001 22:04:56 -0700

You proposed the idea of tapping the batteries.  I would suggest that
that wouldn't be a good idea.  Al later briefly mentioned the big
problem with this -- unequal currents being drawn out of the PC supply. 
Generally the minus voltages are required to supply only a few tens of
milliamps,  The RS232 serial port being a major consumer for its require
plus and minus swing.  On the other hand the + 12 is usually called upon
for the hard disk drive motors and voice coil actuators, so it runs in
the several amps.  The +5 is the real killer.  It runs in the many amps
for the processor and logic.  Additionally on the ATX supply used with
Pentium class machines you need the 3.3 V supply at lots and lots of
current (tens of amps),  You can see the pinout at:

The upshot of all this is that one section of your tapped battery will
be discharged and as you attempt to charge it, you will burn up the
other side trying to send charge current through it to the discharged
side.  And if you've never smelled the odor of an overcharged battery in
the morning, it's not a good one.  (I was in the two-way business in my
early days, and we kept batteries under the bench to feed the
"dyna-grinders" in the transmitters.  Think about that one, old timers!)


Public Seismic Network Mailing List (PSN-L)

[ Top ] [ Back ] [ Home Page ]

Larry Cochrane <cochrane@..............>