Electrical short?

[gcameron]

Recently took VRV on a trip and noticed the battery wires sparking a little when installing battery. Once at camp, battery kept running down when generator was off for a few hours then battery quit. Bought new battery and seemed to work fine but battery was dead after drive home. Both batteries now taking a charge. Ideas?

[charliem]

[font size="3"]It's not likely a short. A true short circuit on the 12V system would blow a fuse or generate a lot of heat. The sparking when you connect the battery indicates there is a load on the system. There are a few devices such as the Propane/CO detector and the fridge control board that draw current all the time. Those you just have to live with, but they're small loads. Look for lights left on like in enclosed outside storage areas.

In addition, if you have a two door fridge with separate freezer there is a frame heater that draws 0.5A continuously. There are fixes for that on this forum. If you have a smaller 3-way fridge make sure it's not set to run on 12VDC. That will drain a battery super fast.

The best way to find the culprit is with an ammeter, preferably a clamp on DC ammeter. If the battery was really dead when you got home after towing it sounds like your tow vehicle is not supplying charging current. That's a problem, but can be fixed. That also can be located with an ammeter or good voltmeter.
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[pinstriper]

Eh, the  only way Charlie's theory holds water is if the battery is already so anemic as it won't hold a charge. Which is an outcome of the situation he describes that goes long unremediated.

But if it started with a healthy battery, something else is going on in terms of a drain.

Loose connections with arcing will drain the batter (and start fires) in a surprisingly short length of time.

But if the battery is weak, yeah maybe "a few hours" is all you get.

I would pay particular attention to (a) a battery of known GOOD health, and (2) what Charlie says about the TV charging the battery in transit, and (c) I'd like you to expound a bit on the whole "battery wires sparking a little when installing battery".

[david]

I have always seen significant sparking when I connect the battery. I have checked the current with a clamp on ammeter and it is very low- a few tenths of an amp at best. So I assume that something- like the CO/Propane detector has a capacitor that charges just when connected but does not draw significant current.

That being said, I would start with a known good and fully charged battery. Terminal voltage should read about 12.6 V. Then hook it up. If you have or can borrow a clamp on ammeter, measure the current. You probably do have a fridge with the frame heater, so if more than an amp, with everything off inside, then you have an electrical problem- the wiring or an appliance is bad.

If you don't have a clamp on ammeter, you can watch the battery voltage over four hours. It should stay up near 12.6, maybe drop a tenth or so. If it drops to the low 12s then you are drawing a lot of current so the wiring or an appliance is bad.

If one or the other of these tests show a problem, then to diagnose it, you really must have a clamp on ammeter. I would physically disconnect each appliance- either by pulling its fuse if it has a dedicated one, or disconnect its wiring and see which one or which circuit is pulling the high current.

Good luck,

David

[gcameron]

I'm a car guy so I think some minimal sparking could be normal. When installing new battery it the sparking was very noticeable, visible and audible sparking, and caused me some concern beyond a minimal load demand. hoping that someone else had dealt with this and an easy fix.

[charliem]

[font size="3"]A word of caution to the electrically uninitiated. If you chose to buy a clamp on ammeter, and I think everyone should, make sure it measures DC Amps. Many lower cost "clamp on meters" only measure AC Amps. Not much use to us campers. I like

[a href="http://www.sears.com/craftsman-professional-true-rms-ac-dc-clamp-ammeter/p-03473756000P?prdNo=1&blockNo=1&blockType=G1#"]http://www.sears.com/craftsman-professional-true-rms-ac-dc-clamp-ammeter/p-03473756000P?prdNo=1&blockNo=1&blockType=G1#[/a]


because it has a 40A scale. That's a practical range for campers and gives useful resolution at low currents.
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