[Milsurplus] 12v -- 24v Vehicle Power

[WA5CAB at cs.com]

Gary,

Your M37 had two 12 volt batteries in series, but it could just as well 
have had a single 24 volt battery, or three 8 volt batteries or four 6 volt 
batteries.  All of those battery types are made up of 2.1 volt cells in series. 
 But you didn't mention having significant 12 volt loads running only off 
of the lower battery.  Therein lies the problem, and the reason for the 
comment.  The system will work (meaning that the 12 volt loads will be happy).  
But the upper battery will be chronically overcharged and may get cells 
boiled dry if you don't check them fairly frequently.  However, if you don't mind 
a shorter service life in the batteries (mainly the upper one except in 
cold weather) it is a workable solution to running both 12 and 24 volt gear in 
the same vehicle.

In a message dated 10/7/2009 10:11:12 PM Central Daylight Time, 
n9zsv at magtel.com writes: 
> Well the government must have thought it worked pretty well as they put 
> it into many 10's of thousands of vehicles for several generations. My 
> 1954 M-37 had two 12v batteries under the passenger seat and a 24v 
> generator that charged them in series. Of course the army had manuals 
> full of maintenance procedures for keeping the vehicles running. Such as 
> checking the specific gravity of the battery cells on a regular basis.
> I bought a surplus 24v generator and regulator and some day I'm going to 
> get around to installing it on my old 1970 Dodge Power Wagon. I can use 
> the pulley slots that were meant for the air conditioner.
> 73 Gary
> 
> 
> 
> 
> 
> Sean Kelly wrote:
> >>The simplest way to go is to install a 24v generator or alternator and 
> >>run two 12v batteries in series. Tap off between the batteries for 12v 
> >>for lights, ignition, ect. When I had my 24v M-37 weapons carrier I 
> >>easily ran any 12v gear that way. Worked just fine till I sold it for 
> >>college money. Damn I wish I still had it. :'(
> >>     
> >
> >
> >  
> >
> >I can't figure out why this combination wouldn't charge one battery too 
> much and the one for 12 Volts too little? -------  Because they are in 
> series not parallel.  ------------
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480