Hi,

I've got a 2010 3500 with a factory trailer wiring harness. I plug my camper into this which connects the tail lights on the camper and also charges the camper batteries. I thought there was an isolator between the two but found out there wasn't when I couldn't start the next day. Had a friend who jumped me, so no problem but concerned about being out in the boonies by myself. Talked with the camper mfg and he said they stopped installing isolators since the hot lead on the trailer connection was only on when the ignition was on. Otherwise, it caused the the isolator to burn out.

Well, I checked my trailer plug and it's always on. Should it be or should it only be on when the ignition is on? If always hot is the design, then I guess I'll need to install and isolator.

Thanks, Bruce

 

My 09 is always on. We would add a continuous duty solenoid on the trucks when we set it up to tow our equipment.

 

thanks, looks like I'll need to add a battery isolator to the camper

 

You could always just put a mechanical switch on the hot 12VDC line and open it up when camping, cheap and easy. Isolators are easy to install also but be careful where you tap to the ignition.

 

What's the concern about tapping into the ignition? Just that is is hot always? My camper uses the trailer connection to connect, so I could just unplug this while doing work and turning off the camper batteries. I like the isolator since I can't forget. I was also thinking of adding a bypass switch so I could slowly charge the truck batteries in an emergency. Wire gauge isn't sufficient to do a jump start but hour or so might be sufficient.

 

Some time ago, I bought a 3/4 ton truck and had a slide on camper. I had the same issue as you so I went to an RV place and had them install an isolator. The idiot that installed it, used one of those ****** with a light on to find a wire that got hot when the ignition was on, well, the wire he picked could not handle the the extra load and it caused all kinds of problems with the electronics. After several trips to the dealer and warranty repairs, I figured it out. I moved the isolator control wire to a better source and everything was fine. The good thing was that when I bought the truck, I told the dealer that I needed an isolator installed and he sent me to the place that did the original work so they didn't charge me for the repairs.

 

Update - I added a Blue Sea 7610 automatic charging relay. Works great for my initial situation. Also allows me to charge the truck batteries when the camper is plugged into a 110 volt power source. But it appears to limit how much the truck will charge the camper batteries. At best I'm getting 12 volts after hours of driving. I'm expecting that I would lose a 1/2 volt due to the diode. But I should be able to charge the camper batteries using the truck to 12 1/2 - 13 volts. So I've got to get out my voltmeter and see what's going on. I'm thinking I need to get a wire that's closer to the alternator as my input into the isolator and not off the fuse panel. Still, when the truck batteries are fully charged, why wouldn't I get a voltage that is closer to what the alternator can put out?

 

Batteries charge at a higher rate than they put out. You'll never get 14v on your battery, which is about what the alternator is putting out. If your alt. is putting out 14.4v and you run your truck for 1hr to fully charge, when you turn your truck off and immediately measure the battery voltage, it'll never be higher than 12.7v as that's the max xharge rate of a battery.(12.68v to be exact)
So, your camper batteries are probably measuring out at about 12v even. This is normal and there's nothing you can do OTHER and installing a bypass across the isolator with a toggle switch, but again, you'll only be gaining that .7v loss from the diode.

You could install a higher amperage alternator that provides a drop down voltage for your truck and the higher voltage for your camper, but that's alot of work and know-how and could get messy in the newer trucks.

 

Thanks for the info. I've only done a little bit of testing but my measurements line up with what you are saying. I get about 12 volts on the camper batteries after a day of driving. If I plug the camper onto 110, which has a charging circuit for the batteries, I get 12.68. Since I don't want the camper batteries to get below 11 volts, I'm thinking the .7 loss because of the diode really lowers my battery storage capacity.

I think I'll add a constant duty NO solenoid that is igniition switch activated as a bypass. That way I wouldn't drain the truck batteries when the truck isn't running. And keep the BlueSea since it does allow me to charge the truck batteries when the camper is plugged in to 110. I like this feature since it allows me to easily maintain both truck batteries and both camper batteries.

 

If this is what you are getting at the battery, then you are only about 50% charged - not good. Here is a table on what you should expect.