Military Vehicles, May 1997,: Re: [MV] Voltage reduction

Re: [MV] Voltage reduction

R. Notton (106363.2514@compuserve.com)
Thu, 1 May 1997 16:39:31 -0400

Hi,

I don't know about wizard but I do stay alive and warm by working on
electronics and two way radio.

Don't tap off one battery or use a plain resistor, the former requires the
unloaded battery to do things it rather wouldn't and the latter is only
good for an absolutely fixed load and battery voltage, neither of which you
have.

I am always fitting two way radios to 24V vehicles and use one of the
commercial regulators, there are two types, non-isolated and isolated. The
non-isolated types are invariably for negative earth vehicles whilst with
the isolated there is no DC connection between input and output and vehicle
ground polarity is immaterial.

Just look through your yellow pages on two-way radio and I you'll find most
companies that are installing will have regulators on the shelf.

As a general point the one thing 12V lead-acid vehicle batteries are not is
12V, expect a little over 12V at rest, say 12.5 or so and up to 14.4V on
charge with the motor running, this means in a so called 24V system you can
expect almost 29V as a supply. Also the ampere-hour rating is invariably
at a very low rate and never quoted! Don't expect a 30AH battery to supply
30 amps for an hour or even 1 amp for 30 hours, the typical test current is
0.1 amp!

Richard
(Southampton UK)

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