Battery disconnect (+ or -)

[Animize]

Originally Posted by 5picker

These threads are always fun but the truth is... it does not matter.

Electrons can't magically jump/flow from a disconnected post (either one) to complete a circuit from the battery. Doesn't matter if you touch a wrench/screwdriver to a hot lead somewhere in the R/V (and also to ground) if the ground cable is disconnected/isolated from the battery. There simply can't be current flow through a cable where the positive or negative is not connected to a power source. (battery)

Put it on either side that is most convenient.

Thanks!

[doanshop]

Originally Posted by NMWildcat

Wow.
It really doesn't matter at all, positive or negative side interrupt, as long as the circuit is disrupted.
I almost always put the disconnect on the ground side as it is usually easier, and 1 cable vs several.
But, do what makes sense to you, as you are the one who has to use it.

2X

[Boomerweps]

There are enough differences between vehicle, RV, and home electric wire color conventions, I say “why add more?”.

House electric, black is death, power positive/hot, white is the angel to save you, negative/return/cold, green is ground. Easy to remember. Then someone decided to use red for hot/positive on vehicles and black for negative/return, usually called ground (using the chassis as the ground/return) usually copied in electronic power circuits, audio, and solar. On RVs, it’s a crap shoot for wire color and the only way to know for sure is with a meter.

Residential electrics place all circuit breakers/fuses/switches on the positive side.

[NavyLCDR]

RV manufacturers install them on the positive side. Since that is where the manufacturers install them, that is where I would too.

[Ramos2400]

How would this work if you have two batteries in a parallel mode. Meaning positive to positive and negative on only one battery.

[WolfPup2018]

If the negative is grounded to the chassis, wouldn’t putting the switch on the negative side become an issue if there was a device not properly grounded? Until you touched it, grounded against something then….BOOMSHAKALAKA

Because ground doesn’t need to go back to the negative terminal on the battery. Why does my toongue lift work with just power and mounted to the chassis ��

[Ramos2400]

How does that apply if you have two batteries in parallel.

[clouse]

can I hook up my disconnect to positive, the answer is YES! That is what I do and have done for 4 years with no problem at all

[NavyLCDR]

Originally Posted by Ramos2400

How does that apply if you have two batteries in parallel.

You put the disconnect on the positive battery cable(s) going to the RV just like you would either a single 12 volt battery or 6 volt batteries connected in series

[Bob K4TAX]

Flip a coin. Heads in the Positive terminal wire, Tails in the Negative terminal wire.

Now if the converter Negative is connected to the frame and the trailer is connected to shore power, the battery switch in either the Positive or Negative won't protect the converter in the event the Positive is accidentally shorted to the frame.

I use the battery switch to select #1 battery, #2 battery, BOTH, or OFF. It is in the Positive battery cables and is located very near the batteries in a waterproof case. If shore power is connected, everything works to the current limit of the converter, regardless of the position of the battery switch. The switch must be on one of the positions to charge the batteries or use any 12v facilities when NOT connected to shore power.

Bob

[clouse]

one battery or two makes no difference on my 2017 Forester

[garywilson]

Originally Posted by Animize

So I'm installing a battery disconnect switch near the battery and I see differing answers.
Can I install it on positive as seen on a youtube video? Or as some say, should I install it on the negative?
Thanks!

Depends on what you want... either will work for you. You seem to have no brake wire or jack wire going to your battery in the pic.

I put mine (a marine breaker switch) on the positive side that turns off everything except the break-away switch and the tongue jack. I then installed another hidden switch for the jack (grand-kids, aren't they grand?).

About the only time I kill the battery breaker is if one starts cooking or I'm working on a 12V circuit.

[Bdjones]

Originally Posted by latner

X2

I'll pile on with my 2 cents.

X3. After having shorted many wrenches, a few wires, etc. over the years, I can attest to the preference of disconnecting the negative side as close to the battery as possible. Reasoning, if the frame is left connected to the battery negative, contact between an energized positive conductor and any piece of the frame will result in a short circuit. Not the case with negative disconnected.

[5picker]

Originally Posted by Bdjones

X3. Disconnect the negative side as close to the battery as possible. Reasoning, if the frame is left connected to the battery negative, contact between an energized positive conductor and any piece of the frame will result in a short circuit. Not the case with negative disconnected.

Just curious... how would a positive conductor be energized if nothing is connected to the positive post of the battery? (take the converter out of the mix for discussion since we are talking BATTERY disconnects)

[Bdjones]

Originally Posted by 5picker

Just curious... how would a positive conductor be energized if nothing is connected to the positive post? (take the converter out of the mix for discussion since we are talking BATTERY disconnects)

I'm saying leave the positive connected and remove the negative. This takes a possible short circuit between any energized positive lead and the frame out of the picture. (Will reread my previous post and make sure my fingers typed what my brain thought.)

[Chuck_S]

There is only one (1) wire to the Negative battery terminal and it runs to the frame just like in your car/truck. If yours is different it's wrong. Trailer or motorhome makes no difference. One wire.

Battery switch on the Negative terminal therefore will sever ALL the battery power. All of it. This is obviously the place to put it for convenience if nothing else but it's more than convenience.

The first step to safely work on a vehicle's electrical system is to remove the wire from the battery Negative terminal. No chance of shorting anything this way as no power can "escape" from the battery.

The pictured (and similar) switches all connect directly to the battery Negative post -- they won't fit on the positive post for good reasons. A separate external switch should be wired the same way. I had a switch like this for years on the battery of one of my SUVs as the battery would die within a week or 10 days when parked at the airport. Nothing like coming back after a week and the truck won't start! Unlock the door, pop the hood, tighten the switch etc. 2 minutes and rolling. Same on the camper although the switch is external.



-- Chuck

[joshuajim]

I have been told by an automotive electronics expert that computers in cars always disconnect the negative side of a circuit. I cannot personally verify this, but the person i know should know this as its his design experience.

He told me that they do that because the current on the negative is easier to control.

Now does this apply to RV’s, probably not.

[darrellr]

All this talk - what side of the battery do you remove when you are working on a car? Negative. That is where the switch should be imo. Power flows from negative to positive in 12vdc systems...it does not "originate" on the positive side as some have stated.

[PhilSR5]

Originally Posted by Animize

So I'm installing a battery disconnect switch near the battery and I see differing answers.
Can I install it on positive as seen on a youtube video? Or as some say, should I install it on the negative?
Thanks!

At first, I put it in the negative cable of the stock battery but as soon as I upgraded it to a 200A/H battery I changed my mind and put it on the positive cable of the battery.

[5picker]

Originally Posted by Bdjones

I'm saying leave the positive connected and remove the negative. This takes a possible short circuit between any energized positive lead and the frame out of the picture. (Will reread my previous post and make sure my fingers typed what my brain thought.)

There cannot be a short circuit in a circuit that isn't connected to a battery.
There cannot be any current in a positive lead when no cable(s) is/are connected to the positive lead of the battery. The electrons cannot jump air.

For your wrench to short to the frame as you mentioned previously, BOTH posts of the the battery would need to have wires connected to them.

The battery is the supply. If EITHER post is disconnected (no wires connected to it) no current can flow from the battery no matter which side is still connected.