Battery on/off -- Pos or Neg side?

[mbtelguy]

Just a caution and something else to consider
when wiring up a battery disconnect switch.

If the switch is in the battery positive side I suggest you
make sure the power to the breakaway switch
is not disconnected, just in case you forget to
turn on the batteries, prior to towing trailer.

If the switch is in the negative side and the battery
ground is open (switch off position)
there will not be power to the breakaway switch.
Maybe this justifies a positive side disconnect
switch wiring.

Gary

[dnaraG_1M]

Originally Posted by mbtelguy

Just a caution and something else to consider
when wiring up a battery disconnect switch.

If the switch is in the battery positive side I suggest you
make sure the power to the breakaway switch
is not disconnected, just in case you forget to
turn on the batteries, prior to towing trailer.

If the switch is in the negative side and the battery
ground is open (switch off position)
there will not be power to the breakaway switch.
Maybe this justifies a positive side disconnect
switch wiring.

Gary

True......If the power switch is off while you're towing.

If parked, breakaway switch is a moot point - as long as
it is not activated!

Is it common to have the power switch OFF while towing?
Had no plans to do that - want the reefer to have 12v power
and propane available.......

cheers,
johnd

[Herk7769]

Originally Posted by dnaraG_1M

Is it common to have the power switch OFF while towing?

Not common at all.

With the switch "off," regardless of which side + or -, you will not have emergency brakes (breakaway switch) OR battery charging from the tow vehicle. You SHOULD have 12 VDC to the camper for the fridge through the tow vehicle's + 12 VDC connection.

[Malco]

Guess people better make sure that's on their checklist so they don't forget to turn it on.

[mbtelguy]

I hope that people are not driving around
with the battery disconnected. However it
is very easy to forget to turn a battery disconnect
switch on.
To avoid this, it is very easy to rewire the breakaway
switch in a way to eliminate this possibility.

In regards to the negative side just think
about how difficult it would be to rewire
the brake circuit to prevent this.

Gary

[dnaraG_1M]

Originally Posted by mbtelguy

I hope that people are not driving around
with the battery disconnected. However it
is very easy to forget to turn a battery disconnect
switch on.
To avoid this, it is very easy to rewire the breakaway
switch in a way to eliminate this possibility.

In regards to the negative side just think
about how difficult it would be to rewire
the brake circuit to prevent this.

Gary

Yep. I see no major downside to wiring the breakaway switch
directly to the battery.And upside if you are as forgetful as I.
Although I'm new to TT, I've pulled flatbeds for decades.
All the flatbeds I've owned have the breakaway switch wired
directly - no cutoff switch. Never had a problem, just put
the plate back into the breakaway switch after testing
the brakes and there's no battery drain........

Rewiring mine to go around a negative cutoff switch would
be a pain - crawling under TT and pulling the hubs - but not
difficult if both magnet wires are available (like all 4 of
mine are).....

Like you imply, that's a good "human factors" reason for
a positive lead cutoff switch......if you wire the breakaway
switch to be always hot so forgetfulness does not equal
disaster.


cheers,
johnd

[Mpjduff]

New to camping in a trailer. Do you need to install a switch? I am not electronically inclined so is it hard. Should I go and disconnect my batteries while it is sitting. I left them hooked up I know they are dead is that bad?

[Witch Doctor]

I agree with iggy's comment, You should always install your disconnect at the pos. side. I was surprised to see in our new Rookwood 8289WS, that I had one. nothing fancy just a push in for juice and pull out for the disconnect. I have installed a second battery and wired it to the first on the op. side of the storage area. I had to install a bigger wire being I did not want a voltage drop. I used another vented battery box, but I put a Tee in the vent tube to the original factory installed vent. I do not like drilling holes in a new unit.

[Mountainmanbob]

Originally Posted by Mpjduff

I left them hooked up I know they are dead

is that bad?

it's not a good THING
to leave them drained (dead) low for long
you might possibly start with
adding distilled water to your battery
then put a charger on it

voltmeters come in very handy
they tell us exactly
what the battery has
we can see how long it holds a charge

note
in most cases that I have seen
if
the battery water has gotten below
the plates in the battery
yes
damage has been done

Mountainman

[sail2liv]

Boat has marine on/off/1/2/or both switch on positive side....has worked fine for 34 years....HOWEVER.....need for fused items on negative side can
be prudent....once in 34 year I had current come in from the negative side and fry all electronic and other items......items are fused on the positive side only most of the time.....so they are protected from high volts/amps on that side but are not protected from the negative side.....food for thought in high voltage storm areas especially when pluged into shore power......when making changes might be something else one might do

[Rod Johnson]

Originally Posted by 07ultra

the reason you disconnect the neg post first on a car is so if your wrench hits the frame on the pos side it won't spark

I'd also say that if your switch requires a tool to operate, put the switch on the ground.

The cutoff in my trailer is on the positive side.
I have cutoffs in all my cars and trucks that sit. That cutoff is always on the negative side of the battery.

Also, I might recall that the pos and neg terminals on a battery are different sizes. So, when you use that plain old cutoff with the green screw knob, it only fits on the negative terminal. But, I could be mistaken...

[Herk7769]

Originally Posted by sail2liv

once in 34 year I had current come in from the negative side and fry all electronic and other items......items are fused on the positive side only most of the time.....so they are protected from high volts/amps on that side but are not protected from the negative side.....

I had to read this several times to get your "drift." I think you meant you hooked up the battery backwards and and cooked a few components, right?

DC current runs in a closed loop. It does not care where the fuse is located. It will blow just fine if it is located anywhere in the circuit as long as it is a high current problem.

Reversed voltage may damage electronics without drawing fuse popping current.

[Bruce and Lynn]

Herk, do you have a make and model of your switch? I want get one of these as well. Thanks

[Herk7769]

Marine Battery 4 Way Switch - Blue Seas Systems 9001e

or similar. I went this route because I have two batteries and wanted the option of isolating one if it malfunctioned without rewiring the battery box.

It normally is BOTH or OFF

Amazon.com: Blue Sea Systems 6006 m-Series (Mini) Battery Switch Single Circuit ON/OFF: Sports & Outdoors

If you only have one battery or want to always treat the bank as a unit.

[jbdbsb]

For current flow it does not matter. Disconnected is disconnected! But, when you disconnect a battery which side do you disconnect first? The Neg. When you connect a battery which side do you connect last? The Neg. When you "Jump" a battery which side do you connect and disconnec first and last? The Neg. Why? A possible spark could ignite battery gases. At least that's what I was taught.
Peace out!
Jeff

[Herk7769]

Originally Posted by jbdbsb

When you "Jump" a battery which side do you connect and disconnect first and last? The Neg. Why? A possible spark could ignite battery gases. At least that's what I was taught.
Peace out!
Jeff

Jeff,

When jumping a battery the final connection needs to be to the Frame of the vehicle (as far from the battery as possible) providing the "jump" so the inevitable spark will also be far from the battery.

You are not supposed to connect directly to both terminals of the jump provider's battery.

How To Jump Start a Car | The Art of Manliness

[TURBS]

My stabs and slide outs are wired seperate from disconnect. Always on.
But never travel with disconnect off.

[Herk7769]

Originally Posted by f1100turbo

My stabs and slide outs are wired separate from disconnect. Always on.
But never travel with disconnect off.

My stabs and slides can be disconnected.
I also have a "kill switch" on my stabs.
That makes a great safeguard for little hands that can cause hundreds of dollars damage by running the landing gear up with the aft stabs down.

Also with the landing gear killed, it will be MUCH harder to back up to and steal.

Never travel with the camper battery disconnected since you will not be able to use the breakaway safety system or charge the battery form the tow vehicle; as F1100turbo stated.

[jbdbsb]

Originally Posted by herk7769

Jeff,

When jumping a battery the final connection needs to be to the Frame of the vehicle (as far from the battery as possible) providing the "jump" so the inevitable spark will also be far from the battery.

You are not supposed to connect directly to both terminals of the jump provider's battery.

How To Jump Start a Car | The Art of Manliness

Sorry, you misunderstood, and I was not clear. Allow me to clarify and be specific. When I stated the Neg, I meant a negative "connection", not specifically the Neg battery cable. Yes, you always "Jump" to the frame. Users put the switch in the Positive side of a circuit (myself included) because it's generally the simplest most advantageous solution to isolating a particular circuit. You have a power or positive lead running through out the vehicle, but the negative is generally a short straight shot to the frame, so adding a switch are other device is far simpler on the Pos. side.

[SALTY]

switch is on positive side