Battery disconnect?

hbravo · 03-21-2019, 07:59 PM

Evening All,

For years I’ve always disconnected the negative cable on my trailer battery between trips to stop battery drain. Friends just bought a new trailer and in their orientation were told that they should disconnect the positive side cable. Which is correct? Have I been doing it wrong fo more years than I’ll ever admit?

TIA!

jasonnorton · 03-21-2019, 08:07 PM

You are breaking the circuit so don't know why it would matter but if there is something I don't know I'd be glad to also learn of a reason why positive over negative.

stateboy · 03-21-2019, 08:34 PM

IMO, stick with yanking the negative side first. If you swing that wrench from the positive terminal you are trying to loosen the cable from and bump or ground your wrench to the frame or some other metal associated to the frame or trailer, you will know quickly with sparking and arcing. You'll say, "That was not a good idea." Touch the wrench to the same metal while trying to loosen the negative terminal cable and you'll never notice the connection occuring.

Stick with the negative side. It's more for safety and not for breaking the flowing current. I may or may not have some personal experience to offer in that arena.

Duke4857 · 03-21-2019, 08:53 PM

X2 stateboy

2edgesword · 03-22-2019, 07:26 AM

I have always disconnected the negative terminal on the battery and when I added a disconnect switch put it on the negative side. I think the recommendation to disconnect the positive is that if you leave the positive attached and happen to be working on something electrical and in the process provide a path to ground you'll have a complete circuit and current will flow.

Ace · 03-22-2019, 10:24 AM

the guy at the dealer I bought mine from, when asked to install a battery disconnect said 'just pull the fuse...why make this any harder than it needs to be". So that's what I'm doing for now....anyone have any thoughts on this?
Ace

Scott91370 · 03-22-2019, 02:11 PM

Yanking the negative if you're pulling a cable is the safest way because once it is disconnected if it accidentally touches anything else will not cause problems.

Ace - pulling the fuse is fine as well. The reason it is different than removing the positive battery cable is that the connections in the fuse holder are protected and will not touch anything.

hbravo · 03-23-2019, 07:15 PM

I think I’ll stay with the negative. It has worked for me for years. I use a wing nut so it removes without tools but can be securely tightened by hand.

njburn · 03-26-2019, 10:05 AM

Ace - I was told the same thing but it didn't cut all of the power. I took it in for service at the end of the season and one of the guys in the yard said that was a known issue (funny because the dealer nor Jayco notified me). I brought it up to the service advisor and he said their solution was to put in a cut-off switch, which I had already done (I did positive & negative). They ended up giving me credit to spend in the store for more then I spent to put them in.

Ace · 03-26-2019, 10:29 AM

I pulled the fuse, but then later putting it back, got an arc. Skip that - i'm pulling the cable until I get around to putting in a proper switch, or just stick with pulling the cable, which isn't all that hard anyway.

RogerR · 03-26-2019, 10:52 AM

I have two cables going to my battery positive. Main power and separate tongue jack. So I was a lot easier to wire in the negative terminal cutoff.

Parcany · 03-28-2019, 08:44 PM

My friend has a Cardinal and his disconnect is wired on the Pos side. He also has a Hitchhiker and his disconnect switch is also on the Pos side. My brand new Jayco was told to remove the fuze to disconnect the batterys from the camper and it is on the Pos side. These all came from the factory like that. So when I installed my disconnect switch I put it on the Pos side and it works like a champ

stateboy · 03-28-2019, 09:44 PM

I think the difference here is that some are talking about disconnecting the battery and some are talking about disconnecting the power. The original post was asking about disconnecting the battery. IMO there is a difference.

I stated my reason in Post #3 why you should disconnect a battery from the negative side. I would follow by then disconnecting the positive cable, disabling the battery from any electrical flow to the trailer. If you are looking to disconnect the power (i.e. place a battery disconnect switch near the battery without battery removal), my preference would be to place a disconnect switch on the positive side of the battery as mentioned in Parcany's Post #12. Here's why.

If I were to put a disconnect switch on the negative side of a battery, there is still potential for current to flow to and through the electrical circuits from the still connected positive battery post. Post #5 by 2edgesword touched on this (although his preference, like many others, is to place the disconnect switch on the negative side of the battery). Current can still flow through the 12 volt circuitry from the positive side of the battery if it finds a ground to connect the circuit. That ground could be a faulty appliance/switch or you fiddling with a 12 volt electrical item to become or cause the ground with a tool touching nearby grounded metal, completing the circuit.

In other words, the positive post pushes the current out and the negative post pulls the current in. So, if you still have a path for current to flow between the connected positive post and the 12 volt appliances/switches, current may pushed out or still flow. Hence, my thought as to why I like the idea of a disconnect switch on the positive side of a battery verses the negative side of a battery. I have not personally installed a disconnect switch on my trailer since I haven't had the need yet. I'll still continue to enjoy reading what the consensus is on this and other topics on this forum. Occasionally, what works for most of us defies logic and I'm ok with that.

**Mustang65** · 03-29-2019, 05:54 AM

Quote:

Originally Posted by stateboy

If I were to put a disconnect switch on the negative side of a battery, there is still potential for current to flow to and through the electrical circuits from the still connected positive battery post.

For a proper install of a "Disconnect Switch" the only connection on the Negative terminal of the battery that is going to ground is the ground cable. If the battery is connected properly, the battery(s) are isolated from the TT.

Don
My Registry

RVing with SOLAR

wags999 · 03-29-2019, 07:46 AM

When I asked at the factory, I was told to disconnect the positive when I put in a disconnect switch. That is what I have done and my local "service guy" I use, an independent RV Tech, he concurred. When you put a switch in a stick and brick, you put it on the positive side also, just makes sense to stop all power at the battery.

Fyouberg · 03-30-2019, 06:28 AM

This is an informative thread, but doesn’t answer all my battery “hygiene “ questions. I ran a 30A circuit out where I park the TT and keep it plugged in all the time. I have not disconnected the battery between trips. I’m assuming that the shore power is sufficient to provide a trickle charge to the battery. Am I violating any best practices?

**Mustang65** · 03-30-2019, 07:28 AM

Quote:

Originally Posted by Fyouberg

This is an informative thread, but doesn’t answer all my battery “hygiene “ questions. I ran a 30A circuit out where I park the TT and keep it plugged in all the time. I have not disconnected the battery between trips. I’m assuming that the shore power is sufficient to provide a trickle charge to the battery. Am I violating any best practices?

Depends on your model year and TT's battery charge controller. The older models, while supplying the needed charge, are not smart controllers and can boil your batteries over time. The newer models have smart controllers and are programmed to properly maintain a battery charge through all stages. An example of my TT charge controller's output is below.

Don
My Registry

RVing with SOLAR

Riich · 04-07-2019, 06:43 AM

Quote:

Originally Posted by stateboy

If I were to put a disconnect switch on the negative side of a battery, there is still potential for current to flow to and through the electrical circuits from the still connected positive battery post. Current can still flow through the 12 volt circuitry from the positive side of the battery if it finds a ground to connect the circuit. That ground could be a faulty appliance/switch or you fiddling with a 12 volt electrical item to become or cause the ground with a tool touching nearby grounded metal, completing the circuit.

In other words, the positive post pushes the current out and the negative post pulls the current in. So, if you still have a path for current to flow between the connected positive post and the 12 volt appliances/switches, current may pushed out or still flow.

This is incorrect. It is impossible to get current flow if either the positive OR negative wire is disconnected. You can't flow out from the positive side unless it returns to the negative side. Again, it's impossible. You need a return path. To the battery.

With that being said, I would have no issue with putting the disconnect switch in either line.

djrainer · 02-28-2021, 12:48 PM

A lot of great replies and opinions. I'm like FYOUBERG above, I'm fortunate to be able to store our trailer (2009 Jayco Jay Flight) on the side of our house where I installed a 30A Service Box. However, when I use my Disconnect, I lose the ability for our Batteries (2) to charge while connected to Shore Power. However, my real question at this point is what years are considered (new models) and how can I test if the 2009 Jayco's have the smart chargers that will not overcharge? Thank you and happy trails to all. Don

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