opnspaces
San Diego Ca
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Joined: 12/22/2004
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beemerphile1 wrote:On a trailer the disconnect switch should always be in the positive/hot line. The supply wire for the breakaway switch should bypass the disconnect and be attached directly to the battery. If the trailer is ever towed with the disconnect off, the emergency braking system will still be functional. If the disconnect is in the negative/ground line the emergency braking system will also be disabled.
I was going to argue the point with Beemerphile on this one as in a 12V system it shouldn't matter which wire you disconnect. But in fact he is correct that a disconnect on the negative side will prevent the emergency breakaway from energizing if needed. So if you have electric brakes on your trailer (which probably most of us do) then you should put the switch on the positive wire and run a separate fused positive wire to your brake breakaway switch.
I do feel though that I have to argue that if you do not have electric brakes then it should not matter which wire you disconnect. as the running and brake lights receive power and ground from the tow vehicle and not the trailer battery.
That said I'm now going to go edit my original post to reflect my new found realization.
1996 Suburban 4x4. 350, 4.10 3/4 ton
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robsouth
Covington, GA
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Joined: 06/20/2004
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I got my disconnect at Walmart in the battery department. I think it was about $6.00. Had it for several years and it works well.
"Sometimes I just sit and think. Sometimes I just sit." "Great minds like a think."
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mowermech
Billings, MT
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Joined: 06/28/2003
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Well, maybe...
IF you remember to turn off all 12 VDC lights and appliances, there will be no spark, or at worst a very small one. The memory in the stereo draws a very small amount of current.
IF the battery box is properly ventilated, there will be no explosive vapors or gasses.
But then, what do I know? I have only worked with batteries in aircraft (24VDC), forklifts (36 and 72VDC), vehicles (6, 12, and 24VDC), golf carts and people movers (12, 24, and 36VDC)
I certainly don't qualify as an "expert" in battery wiring and maintenance!
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mikeb9550
MI
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I bought a cheap harbor freight one but never installed it. I heard that they break and that is one thing I dont want to have to deal with from saving a few dollars. The other thing is loosing the keys. I was going cable them to a hole but decided to buy a decent race car switch. I mounted it to my trailer frame. I will try to take a pic tomorrow if you would like. Im really happy with it. The only think I have to do different is wire my jack to it instead of the battery. That way I cant hook up without forgetting to turn the fridge on. No DC and the fridge wont work. I am real happy with how it turned out.
http://www.ebay.com/itm/Battery-Disconnect-Switch-Panel-2-Terminals-Longacre-Master-Cutoff-Kill-/170739453992?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item27c0dd5028
Mike
2006 Ford E350 Van (standard length)
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2006 Jayco Jay Flight 26BHS
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ROBERTSUNRUS
Lakewood, Ca.
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mowermech wrote:
Well, maybe...
IF you remember to turn off all 12 VDC lights and appliances, there will be no spark, or at worst a very small one. The memory in the stereo draws a very small amount of current.
IF the battery box is properly ventilated, there will be no explosive vapors or gasses.
But then, what do I know? I have only worked with batteries in aircraft (24VDC), forklifts (36 and 72VDC), vehicles (6, 12, and 24VDC), golf carts and people movers (12, 24, and 36VDC)
I certainly don't qualify as an "expert" in battery wiring and maintenance!
 Hi, as an automotive mechanic at new car dealerships since 1968, I have seen many batteries explode. I even blew one up myself. Ventilation didn't help on vehicles with their hoods wide open either. It's the gasses in the battery, caused by charging and jump starting weak batteries, that makes nearby sparks, blow up batteries. A little spark won't blow up a battery that hasn't built up these gasses. (note: I said, "on a hot or freshly charged battery")
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mikeb9550
MI
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Here is my battery cut-off switch
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roguegaston
Earth
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Joined: 07/01/2010
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On our Lance 2185, which as a BAL/Norco frame, I installed a BlueSea switch in the existing frame holes. It was a bolt on using fender washers. Here are a couple of pics.
Jason
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Crazyfoe
USA
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Joined: 04/13/2004
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skipnchar wrote:The EASIEST disconnect switch is to simply remove the negative lead from the battery. Using a thumb screw on the terminal means it's a 5 second job and 100% effective.
+1 on this! Why complicate things imho.
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