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RE: Wiring a 12V system in a trailer

To: "Mark J. Andy" <marka@telerama.com>, <shop-talk@autox.team.net>
Subject: RE: Wiring a 12V system in a trailer
From: "Randall Young" <ryoung@navcomtech.com>
Date: Tue, 23 Sep 2003 12:10:01 -0700
> I'd been assuming that I'd just put one or two deep cycle big 12V
> batteries in there along with the winch, wire that into the existing 12V
> power circuit (and probably add some 12V cigarette style outlets & a car
> radio) and we'd be good to go.  When the trailer was plugged into the
> truck, the batteries would charge, when I was using the winch the current
> would come from the local batteries, the breakaway would use the new
> batteries, etc.

Mark, I ran a similar setup on a camping trailer for several years, it
worked well enough.  You'll want be sure the wire from the truck alternator
to the trailer connection, and from there to the trailer battery, is fairly
heavy gauge stuff, as it's resistance will limit your charging rate.  Having
a fusible link at each end is probably also a good idea, although I didn't.
The main hazard IMO is that you can run the truck battery down from the
trailer, if you leave the truck connected.

> Is that too simplistic?  What's the 'right' way to do this?

Better IMO would be to add a battery isolator (basically two big diodes
mounted to a heat sink) so the trailer battery isn't connected to the truck
battery; but the alternator can charge both.  Most camping supply houses
carry isolator kits, however check first to be sure your alternator can
tolerate one.  Some can't.

The ultimate I suppose would be a separate alternator, that sensed the
voltage at the trailer battery and was calibrated for a deep cycle battery
... but that seems a little much ... <g>

> In a similar note... The trailer is wired for 110VAC as well.  Currently
> there's a little door through the side of the trailer where you can pass a
> cord out through.  This is kinda a pain (the door opens into a cabinet
> that sometimes is hard to get to) and I'd like to put an outdoor style
> receptical on the side of the trailer so that I can just plug the cord
> directly into the easy to get to recepticle.  What's the right way to do
> this?

I'm not sure I understand the question, there should be a cord permanently
attached inside the little door, that you just pull out and connect to an
outlet.  Are you saying the door is just in an inconvenient location ?

Anyway, I've seen power entrances that basically consist of a male plug
permanently mounted under a spring-loaded cover.  Sorry, don't know where to
buy one offhand, try a trailer supply house.

Randall





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