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Old 04-01-2016, 09:37 PM   #11
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Battery Disconnect Switch

Originally Posted by 25FKS View Post
In many forums. one has to get to the fact vs opinion. A review of the previous post have some validity, but ... I'll try to help.

The switch MUST be on the Positive lead and as close as possible to the battery. If not, you still have a HOT battery that can cause a short, .... Granted the circuit would be open, but if you touch ANY positive wire inside to ground, you WILL have a complete circuit and .

So this video is wrong?

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Old 04-01-2016, 10:05 PM   #12
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Another video recommending negative side

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Old 04-01-2016, 11:25 PM   #13
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25FKS, have a question for you.

If the battery negative has been disconnected, how can you possibly have a complete circuit by touching a positive wire inside to ground. Unless those negative electrons are floating through the air to complete the circuit.

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Old 04-02-2016, 06:56 AM   #14
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Generally most of us are attracted to the positive side of a battery and totally forget about the return path through the negative. Most mechanics will disconnect the negative when working on a vehicle. On an RV, disconnecting the negative will insure that all loads are disconnected, including those that go directly to the batteries without going through the battery control center, disconnect switch, etc.

I go with disconnecting the negative since there are lots of way that you can inadvertently short a wrench from the battery to any point on the chassis.

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Old 04-02-2016, 07:29 AM   #15
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After watching the videos it looks like the negative side is the way to go. I do wonder however if the frame is used for a ground anywhere? I guess, there really would still not be a path back to the battery. A question I really thought would be easy, just does not seem all that easy. I guess I can go one way and always change it later on if I need to.
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Old 04-02-2016, 07:55 AM   #16
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As there is no way to guarantee what someone does / mods installed, ... or something happens over the years, .... The safe way is to remove power! If you have worn, bad, replaced wiring, ... list goes on, there seems to always be a way for power to somehow find a way to ground eventually.

The only safe way is to remove power completely with the shortest wire path. BTW That is what circuit breakers & panels do. I won't go in circles/debates here - Do whatever you please. I just offered my assistance and years of experience, I do not need ____. I'll leave that to Politicians. Last post on this subject.
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Old 04-02-2016, 08:43 AM   #17
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I'm so glad others addressed the, I can't say because this is a family place, given here.

The disconnect is usually on the positive side for convenience, the ground usually comes out of the battery box, runs about a foot and is solidly connected to the frame. The positive side is routed out of the box, along the frame, to the breaker where it's then distributed throughout the unit. It's easier to add the disconnect to the system right next to the breaker. Here it doesn't matter which side is disconnected, but to disconnect the ground it would require extra work that isn't necessary.

The statement about mechanics pulling the ground first and connecting it last is true for a few reasons. If we drop a wrench on the battery, then yes it can hit the fender, ground out and be a problem. The battery is surrounded by grounded metal, so by pulling the ground, you make that metal inert.

When working with the ground first/last it's safer. There is most always a spark when completing the circuit, when connecting the ground the spark flows from the battery to the cable and is dispersed through the framework, but when connecting at the positive it flows from the cable to the battery which at that proximity could cause a problem if the battery has been gassing. The spark created by connecting the positive last is much larger compared to connecting the ground last. Within the confines of a disconnect switch this is a moot point.

Finally, auto electronics are designed to wake up by seeing the ground last. Believe it or not, they are sensitive to it and while the exact how's and whys are best explained by an engineer in Detriot I know you can put a car in logic lock by improperly installing a battery. I've fixed several simply by pulling the ground cable, discharging the entire system, and reconnecting the ground. This isn't an every car every time problem, but does exist.

In the RV world, so far as I'm aware with towables, we don't have those issues, which is why it's still okay to switch the positive. It's absolutely best to put the switch on the ground side, but there's not enough difference to justify adding that much cable to put the switch in a convenient spot.
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Old 04-02-2016, 09:37 AM   #18
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My camper and boats have the perko cutoff on the positive side and close to batteries.

On my boat i use my perko switch to disconect, use one battery, OR the other, or both combined. Can't really do that if your hooked to ground wires. Besides that, its all about eliminating sparks in boats.....or things can go boom!

Vehicles and equipment.....disconnect the ground from battery.
Campers and boats........disconnects on positive.
Thats what I've seen and recommend!
( like most have already stated)
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Old 04-02-2016, 09:45 AM   #19
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I would have said Negative but could see where Positive may be chosen especially if cutoff is for a portion of the circuit.

The battery mount type I must agree need to be Negative mounted for safety reasons. The Positive should always be protected if exposed. Marine and most cars today have red covers over the positive terminal to prevent accidental contact. The negative off first and on last is why I would side with the Negative side of the discussion.

On the Positive side I see my Coachman Class "C" wire diagram has Cutoff on the Positive with a few circuits still powered when cutoff is OFF.

I believe there may Not be a all inclusive correct answer. Correct may be when done safely for the needs of the unit. Trailer would have some different considerations than say a Motorhome.
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Old 04-02-2016, 09:55 AM   #20
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The battery disconnect on a marine and camper application on the positive side, may also be because both are often times charged with built in chargers.

Vehicles usually are only charging while they are running.

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