Battery disconnect for dual 6V battery system

[audio1der]

I installed an inexpensive battery disconnect on the neg side(neg out to the trailer, not to the pos of the other battery) of our dual 6V battery setup yesterday, but nothing I did with the disconnect key would kill the power??
Did I go about this wrong, or should I just replace the disconnect switch?

I want to be able to disconnect power while in storage without opening the battery boxes.
Thanks!

[Bob Landry]

Put the switch somewhere close to the batteries on the POS side. I know someone is going to come back and argue with this, but ABYC says for the marine industry to do it that way, that's the way the OEM builders install them, and that is the way I install them. The reason is that it guarantees that all 12V power will be removed from the systems. It is possible for a ground to be picked up from another source and I've seen entire wiring harnesses burned up from an engine drawing starter current through it because of a bad ground, AKA no ground. I know that's not going to happen on a trailer, but it's just an example of why to do it a certain way.
Leave the breakaway switch wired directly to it and anything else that you want to operate with the battery turned off, such as the power tongue jack. The purpose is to remove parasitic loads that will drain the batteries over time.

[JRTJH]

Installing a battery cutoff switch is a fairly simple, straightforward task. There are a couple of things that might have happened. First, is your RV plugged into shore power? If it is, you'll still be powered by the converter regardless of what position the switch may be in. Second, you might have a bad switch, or if it has 3 connections, you may be on the "constant on" terminals. Disconnect the switch and check it with a continuity tester to make sure it's funcitonal. Here's a simplified schematic for what you should have when you're done with the installation.

I agree with Bob with regards to installing on the positive side in marine applications. Boats have an "inate ability" to sit in water and create their own ground because of the water. As he said, that's not going to happen on a trailer. All 3 of the major automotive manufacturers, in their owner's manuals state to remove the negative battery terminal at the battery for extended storage. We were looking at new Cougar fifth wheels this past weekend (It's a long story) and every one of them had the battery cutoff switch wired to the negative side of the battery.

I suppose it really doesn't matter which side you install the switch, positive or negative, it's really up to you. One side may be more easily accessed or fit your switch location better. The main objective is to remove power to the RV and so far, it seems you're having issues with that.

[audio1der]

Thanks guys. I was thinking the radio is still connected to ground so I may have to switch the leads around so it interrupts +12V instead.
There are only 2 connections on the switch; on/off and the unit was not connected to shore power LOL
I have a degree in electronics engineering and have been playing with car audio since before I had a car so I'm comfortable with DC but dual 6V is new to me and I want to be careful with our new investment

Thank you again for your input/opinions!

[JRTJH]

Whether the radio is still connected to ground shouldn't matter if the battery system is disconnected, there's no way to get a complete circuit.

Sometimes the obvious is just not easy to see, especially with lots of experience (makes for overlooking the things we "know" don't need to be checked). Essentially, with a dual battery 6VDC system, the + end of one battery and the - end of the other are electrically the same as the +/- ends of a 12 VDC battery. There's nothing different except the number of "black boxes" hooked to those +/- end terminals. Good luck.