Can someone help and tell me how I hook up my battery disconnect here. Hopefully you can set in the picture there is a black wire that goes to the positive terminal and a jumper cable that goes to the positive terminal on the second battery. There is a white cable that goes from the camper to the negative terminal on the second battery with a jumper cable to the negative terminal on the first battery. So I thought if I took both leads off the negative terminal and put the disconnect there it would cut the power. But I still have power. Help

 

Are you still plugged into your shore line? If you break the battery to frame ground, you kill the battery power, but still will have converter power.

Steve

 

Are you still plugged into your shore line? If you break the battery to frame ground, you kill the battery power, but still will have converter power. The disconnect goes between the negative terminal and the frame ground.

Steve

 

It is not plugged into the shoreline. I will look for the ground. Thanks

 

I would (and did) put the disconnect on the positive lead.


there can be enough metal mass in the frame to provide a ground for smaller draws like keep-alive memory in a radio.


if you break the positive, you have no where for the electrons to go. but if you break the ground at the battery, you can still have enough electron flow from the frame to kill the batteries.


just my 2¢

 

I like this one.

 

So the suggestion is, with the ground off the battery broken small amp draws are conducted through the frame to where? Are you suggesting to the earth ground or the battery ground?

Is there a link you can supply that explains this?

Let me add this. In reality, I have seen it done both ways multiple times and doubt it makes two cents worth of difference. I am only curious about the explanation as to why the positive.

How is putting a disconnect on the ground any different than pulling the ground lead off the battery?

Steve

 

I have been researching this issue on the Internet and it is really interesting. As I suspected there are as many folks who argue for it one way as the other. I am back to "flip a coin" or show me something that demonstrates it makes a difference in the real world.

Steve

 

you are probably right in that it may not make a difference in the real world.


The phenomena I'm referring to is called Capacitive Ground (at least as I was taught). a google search didn't turn up much for me, but I didn't try real hard.


If you think of the way electricity works, it makes sense. electrons flow from (-) to (+), while current flows from (+) to (-). so when it comes to grounding, a couple of weird things like this can happen.


I tried to find it last night, but a few years ago there was a post in the dentside forum about a guy who had problems with is radio turning off when he had his headlights on. it would work fine all day, and then turn off the instant he turned on the head lights. As best I can remember, the root of the problem was the ground strap from the frame to the cab was in poor shape, and the cab lights and radio were both grounded to the cab. So there was enough ground capacity to run the cab lights, or the radio, but not both. The ground field became saturated with current and there was no path for it to return to the source (B-).


another reason to not do the disconnect on the (-) side of the circuit is the potential for a goof up when you hitch the trailer to the vehicle. if there were some reason to have all the power disabled in the camper (e.g. electrical problem), then you would have the ground path restored through the ball on the trailer even if you don't hook up or disable the charge wire on the TV. you would have to physically remember to unhook the B+ wire on the camper in order to kill all the power.


The two exceptions I can think of, off hand, are a boat and disconnecting the battery cables in a vehicle. in a boat, the negative post on the battery is the entire ground field. almost always (except on the motor), all of the wiring comes back to the negative post via buss bar, rather than grounding in random around spots around the boat as a chassis ground (particularly if it is Fiberglas). so in this case, disconnecting the negative makes good sense. When disconnecting a battery, it behooves one to disconnect the ground first, unless you have an insulated wrench. invariably, if you try to do the (+) post first, you will touch the wrench to ground and get a great visual demonstration of what a "dead short" looks like. while that can be great source of entertainment from afar, it isn't much fun to do. so in this case, killing the ground first for safety reasons makes good sense as well.


Theory aside, if you look at all of the wiring in your camper or truck, all of the fuses are on the (+) side of the circuit. In most cases, it is safer to kill the current potential coming into a circuit (+), rather than try to kill the electron flow coming into it (-).

As I said, it the real world it might not make much difference. If I get time, I might give it a try though. I've got a radio with keep alive memory in the camper so I could test it there. if it remembers the time and radio stations with the (-) disconnected it would support my reasoning. but truth be told, I'm not sure that an ultralight with fiberglass sides will have enough ground capacity to make it work.

 

I have done it both ways in the past. I focused on the ground as that was what the OP started with and I was trying to chart the same course to keep it simple.

The one comment I found when I was searching was " I just put it on the one that is easiest to get to". I guess that is kind of where I stand. On a clean slate, I would put it on the positive, but working aftermarket sometimes it is just requires less work and so far, knock-on-wood I have never had a problem. Of course, for long term storage I always pull my batteries, so it is kind of a moot point for me, maybe not for others.

Interesting regardless,

Steve