From: chance wolf (chance_wolf@shaw.ca)
Date: Thu Dec 11 2003 - 23:41:46 PST
----- Original Message -----
From: "cliff matushin" <deuce6x6@hotmail.com>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Thursday, December 11, 2003 9:58 PM
Subject: [MV] a simple m35 voltage question
> I recently put a voltmeter across 1 battery in my deuce and of course the
> potential was about 12 volts. Then I started the engine, and the voltage
> went up to about 14.5v. Question: why can't I run a primary wire from
this
> first battery to 12 volt devices and use the common ground? seems so
easy,
> it must be wrong. Cliff Matushin, SD.
I thought that too back when I was installing cellular telephones, until I
tapped off the one battery in series in some Hitachi excavator and blew up
the charging system a couple of days later. The way it was explained to me
then is that you're unbalancing the charging system by having an extra load
on one battery in the series, which will then cause the other to overcharge
(or in the case of this Hitachi's electronic system - bake something buried
within some epoxy-covered module which costs $1100.00 to replace.) Either
way, Not A Good Thing.
Others have told me that a small imbalance (under 3 amps, from what I
remember) won't hurt much on the standard military 25A and 60A systems, but
obviously doesn't hold true for some of the electronic ones, or a certain
Hitachi excavator wouldn't have minded a celphone which drew about 2.8 A
full transmit. Go figure.
Others on this list have had more experience with this than I. I do know
that in the Canadian Army, things like the M62 and M816 wreckers and other
24V equipment frequently had 12V beacons and lightbars installed so as to
run off the first battery in series, and those things draw a fair bit of
current. Probably also explains why you can smell the high-side battery
boiling when the rotators are going too - unless it's just my pessimistic
imagination. ;)
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