[Milsurplus] 12v -- 24v Vehicle Power

[J. Forster]

Sean,

The charge WILL be unbalanced as you suggest.

Aside: This exact problem was addressed in the Canadian WS 19 Mk III Power
Supply. It's really very clever:

The dyno (which must be used on transmit, not necessarily receive) has 4
sets of brushes: 2 pairs of 12 VDC input brushes, one pair on each of two
separate commutators; and two pairs of brushes on two separate
commutators, one for HT1 (275 VDC) and one for HT2 (540 VDC). The outputs
are conventional.

However, the input brushes can be connected in parallel for 12 V
operation, and in series for 24 V operation. The cleverness is in the
series connection.

If there were two separate dynos in series, uneven loading would result in
uneven voltage division between the inputs to the two machines. However,
since the two machines are MECHANICALLY coupled (they are on  common
shaft) the input voltage is forced to divide equally. You can look at it
as a center tapped autotransformer for DC. Very clever, IMO.

Best,
-John

===============

>
>> 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?
>
>
>
> Sean