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RE: [RC] LQ HOT chassis and Dead Battery 2 - David LeBlanc

Roger said:
If your battery dies when parked. Make sure ALL circuits are off. Most 
LQ rigs have a main battery turn off switch. Park the rig, disconnect 
from the truck, turn off the battery. Test the battery with a DC 
voltmeter - should read 12.4 to 12.6. Note the reading to xx.xx digits 
if you use a digital voltmeter.

Turn on the battery switch. Make sure ALL DC appliances are OFF or 
disconnected. Look at the volt meter. If it reads lower, there is a 
bleed off leakage. 

In another life, I was a car mechanic, and specialized in electrical
problems. If you're trying to find why a battery keeps dropping, I do this:

1) Most likely problem is the battery needs replacing, like Roger says in
the part I snipped. Take the battery out, charge it, put it on a battery
tester - any decent battery place will have one. If it holds up to this, the
battery is not usually the problem (though batteries seem to have a nearly
infinite number of ways to fail).

2) Maybe someone sold you too small a battery. We did this once. Battery is
fine, trailer is fine, just isn't big enough. Battery capacity is measured
in amp-hours. Difference in cost between a 95 ah battery and a 135 ah
battery could only be about $20, but can be the difference between making it
through the night or not.

3) While looking for voltage drop might help if something really bad is
happening, a better approach is to measure the amp draw. For example, a
typical car might draw around 35 milliamps with everything off, and if only
started infrequently will be hard on batteries and alternators. Divide
amp-hours by amps draw, and this gives you the time to when the battery is
completely dead. A decent meter will deal with up to 20 amps inline, and if
you're pulling more than that, something's really wrong. If you do this at
the fuse panel, you can usually check it one circuit at a time.

If your problem is too small a battery, the way I dealt with this relatively
cheaply was that I got a plastic battery box, and had a pair of cables made
with a quick disconnect between them to make connection and disconnection
safe and simple (wife-friendly - you really do NOT want to cross-wire
something like this - batteries can EXPLODE, SPEW ACID EVERYWHERE AND
BURN!). This is the system a race car might use. This way, I was able to
take the battery that was too small capacity I messed up and bought, pair it
with the new one that was the right size, and now I have over 200 ah
capacity, which can usually get me through a weekend in a large LQ with no
generator or charger at all. I'd like to have another nice aluminum battery
box, but this method only cost me about $40-50 for the battery box and to
have the cables made up.

BTW, Roger's advice on the solar panels is really good - thanks for the

Oh - something else from when I worked as a mechanic. This gizmos that
charge the trailer from the host vehicle are not at the top of my favorite
things list. Seems they malfunction a lot, quit charging, suck the battery
down on the host vehicle, all sorts of badness. Maybe they work for you, if
so, great. Maybe they make them better than they did 20 years ago when I was
fixing cars. I do not like them, and if I had one, I would make very sure to
unplug the trailer from the truck so I knew the truck would start when I
need to leave. Or perhaps my boss at the time always bought cheap ones that
didn't work well, annoyed him, which in turn annoyed me. YMMV.

Hope this helps...


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[RC] LQ HOT chassis and Dead Battery 2, Roger Rittenhouse