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Topic: 12 VDC Electrical grounding question.  (Read 339 times) previous topic - next topic

12 VDC Electrical grounding question.

No electrician here but can install a bulb and turn on the lights sometimes.  I found this on the net (Connect multiple DC sources to common ground) but still not too sure. I know more than few of you  have shocked some people here and there in your lifetime so I turn to you with this question:
I am trying to get 12VDC to my new RVi battery charger via the 7 to 6 pole umbilical cord. For the RVi Towed Car Battery charger to work it has to get 12vdc (+) from the RV and also the 6 pole plug on the towed car has to be grounded.  If i use the same ground source that is coming form the RV in to the towed car 6 pole plug by T-ing of off it and grounding it to towed car chassis I will be creating a one common "bus" Ground path. Would this create any problems, fire, a bomb?
Positive (+) source are separated at each side one on the RV and one on the towed car and in no way and shape they are connected.
All this would have been much less complicated if the RVi towed car batter charger supplied a ground side cable but did not only (+) to further clarify, RVi battery charger box (device) has 3 cables a (-) & (+) pair that gets connected to towed car battery to be charged and only one (+) to be connected to the power source from the RV.
Thank you,
AL
Former 2003 GV U295 (6230) (2015 - 2025)
Former 94 GV U225 (2013-2016)

Re: 12 VDC Electrical grounding question.

Reply #1 –
Al, where are you locating the charger? Is it in your car? Is there a grounding point on the charger beside the negative wire? Is the installation guide any help? Does your coach have a six- or seven-wire plug? Our coach has a seven-wire connection on the coach but uses a 7-6 adapter for the towed. I think that one of those seven terminals is +12vdc, either switched through the ignition switch or hot all the time, but it is raining out and I don't really want to go out now and check.

I suppose that, if it comes to it, you could run a pair of wires from your coach back to the charger, one being +12vdc and the other being a ground. If you do that, the hot wire would come from a switched source and the ground could connect to any convenient ground on the coach. You will have to check your documentation to see how much current the charger will draw and use the proper size wires. Put the proper size fuse in the hot side as close to the source as you can. Ideally, you would use an in-line fuse holder, so one end would go to your source and the other end to your hot wire, with the fuse in the middle. That can be a physically weak connection, so be sure to support the connection point well. I'd use a wire nut to hold the two wires together, then put electrical tape all over the joint, and use a couple of zip ties, one on either side of the joint, to support it. Of course, that assumes that there is a convenient support handy.

If you can't easily get to a switched power source you could always add a switch to your circuit and come off of the start batteries. All that means is that you have to turn the switch on and off when you are connecting and disconnecting the towed.