Battery and charging questions

[almost13ranch]

I have a 1998 Hallmark slide in camper, new to me. It has 1- 12v deep cycle on board that's about 6 months old. With out any lights or the refrigerator on, the battery will go dead in about 1 day. It will also discharge both of the truck batteries if it's plugged in as well. I have a new in the box ( although I bought it many years ago) isolator, but it's only rated at 70 amps. I think that's too low for the truck as it has a 136 amp alternator. Is there anyway short of unplugging the 7 way cord to prevent discharging the truck batteries? Also is it common for there to be a loud click when you unhook and hook the battery up? The only things that I can see that are powered on all of the time are the propane and CO alarms. Is it common for there to be a key switch that will isolate the camper battery? I have a key switch by the back door that I can't figure out what it's for.

[RV Roamer]

I suggest disconnecting the battery and putting an ammeter in series to find out how much current is actually being consumed. Sounds like it must be several amps all the time.

[DonTom]

Also is it common for there to be a loud click when you unhook and hook the battery up?

If that is a relay clicking, that could be a clue that there are things on and drawing current when they should not be. A good place to start is to find out what's clicking. Is there much of a spark when you connect and disconnect the battery? That's another clue.

                                                                           -Don-

[almost13ranch]

I just got a closed loop ammeter, I'll try that and see what it says. The clicking does sound like a relay. The battery is on the outside of the camper and the clicking is coming from the inside. I'll see if i can get an extra pair of hands to help me find the sound. There is some sparking when I hook up the battery. There are 3 wires that hook to the positive, and 3 for the ground at the battery.

[DonTom]

I just got a closed loop ammeter, I'll try that and see what it says. The clicking does sound like a relay. The battery is on the outside of the camper and the clicking is coming from the inside. I'll see if i can get an extra pair of hands to help me find the sound. There is some sparking when I hook up the battery. There are 3 wires that hook to the positive, and 3 for the ground at the battery.

Remove the three wires from the positive of the battery. Try each, one at a time and find the largest spark. Then ONLY connect the OTHER two, leaving off the one with the largest spark. Then find what does NOT work in your RV. That will be what's drawing most of the current.

-Don- SF, CA

[John From Detroit]

A loud CLICK sounds like an isloator relay (solenoid) cutting in.  you may have one mis-wired.

You can add a switch in the truck/camper battery line, (manual switch) and in fact.. I think you should.  A good heavy switch such as a marine battery disconnect switch.


The battery going dead in one day without Shore or generator power is about normal.  The theory is you use the genny in the day to charge 'em up and power stuff and the battery need only run the rig during quiet hours..... of course a solar roof might help too

[almost13ranch]

Would an isolator relay be in or by the converter box? I'm going to put on a solar charger, but I want to make sure the drain won't be more than the solar can keep up with. I'll try to run some of these tests as soon as I can but I've been working a lot of hours and haven't had much time. I'll try this weekend and post the results.

[RV Roamer]

In a truck camper, I think the isolator, if any, is more likely to be in the truck than the camper. It is usually close to the alternator.

[John From Detroit]

I agree with Roamer on the isloator

I just recalled however that at least one make of converter had a transfer relay.  This converter (Magnatek) has a charger section which is just a few amps, single stage, and a converter section which is often 40 or more amps and runs lights, water pumps, blowers and all non-electronic 12 volt stuff

There is a relay that selects "Converter" or "Battery" option for the stuff that does not need filtered DC like the radio.

[almost13ranch]

Well,  here's what I found out. There isn't an isolator on the truck, and that's the only way it would work is if it was. I checked the amperage on all three wires and found that only one is doing all of the work. I don't know what the others are for, but everything only works off of the one wire including input charging from the converter or the truck. I found that the click had something to do with the mystery switch outside of the back door and the sound was coming from the converter. With the switch on and everything else off, it was drawing 0.89 amps. With it off, the draw was 0.18 amps. The only thing that wouldn't work with the switch off was the electric jacks. As for the problem of draining the truck batteries, the switch for the refrigerator is very stiff, and I suspect that it was still in DC mode, and that is drawing 13.5 amps, causing the truck batteries to drain overnight.  As far as isolating the truck from the camper, the simplest and cheapest thing to do would be to unplug the camper from the truck when camping. I have ordered a 15 watt solar panel and controller, and I think that the 2.5 watt draw with everything off will allow me to maintain the battery and provide a small amount of charging. Thanks everyone for your help.

[John From Detroit]

Sounds like a plan, that switch is likely to "lock" the jacks so that nobody plays with 'em when you are parked (A very good thing) and if so the CLICK is a solenoid pulling in, the current sounds about right.

You can get isolators, they come in two different types. (Basically) at most auto/RV stores

one is a diode isolator, this is a metal box, may have an Epoxy center, several bolts (At least 3 big ones) stick up out of the epoxy,  Alternator/Engine Battery/Trailer line.  There may be a smaller bolt as well, this goes to the voltage regulator.

The other kind is a solenoid isolator. looks for all the world like a ford starter solenoid, is not, there are internal differences.  But the hook up and operation are a lot like the Ford part too

The biggest difference... The starter soleniod is designed for not more than sixty seconds of continuous engagement, the isolator more than 60 hours