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Old 06-03-2014, 07:43 PM   #15
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2003 25' Safari
Riverside , California
Join Date: Nov 2012
Posts: 234
You always want your protection as close as possible to the power not the load.I would use a resettable circuit breaker of the same type that solar installers are using.Size it according to the wire size used.Your goal is to protect the wiring against any source of over current

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Old 06-03-2014, 08:13 PM   #16
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2010 30' Classic
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South of the river , Minnesota
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Originally Posted by GaryC View Post
This is good stuff, thanks for all the advice, but it brings up another question...

A few of you are mentioning putting a circuit breaker on +12v line between the tow vehicle and the trailer battery:

1. Usually circuit breakers (or fuses) are for a safety reason to prevent overloads, but in this case what could cause an overload? I'm wondering what would be the potential cause of the failure and it's effect. i.e., the car alternator going crazy causing the trailer battery to blow-up?
a. Collision damaging the wires causing them to short. This is the most serious concern, and is the main reason we have fuses in cars.

b. Damage to the trailer umbilical due to it getting caught on the hitch during a tight turn.

c. Rodents.

d. Plugging in some other trailer that is wired wrong (or, to be charitable, differently)

2. Could this circuit breaker be the same type used for AC? i.e. I have an extra slot in my WFCO Power Center for another circuit breaker, so could I use this for the 12v battery line?

Thanks! Gary
No, DC fuses and breakers are different. I have been using self-resetting stud-mount breakers, which is what Airstream uses. However, there have been reports of these failing to open on a dead short, so I've used fuses on my last project.

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Old 07-19-2014, 08:35 AM   #17
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1958 18' "Footer"
Idyllwild , California
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Posts: 534
I would suggest that you check the Wiring at the Rear of the Jeep with the 7 Pin unplugged. Check my attachment to find Terminals #1 & #4 with a Volt Meter or even easier with a 12 Volt Light Bulb with short pigtails (easy to make and fairly inexpensive but very valuable). You most likely have 12 Volts there even with the Ignition Off.
Agreed to be sure that the 12 Volts Power source should have a Fuse or Circuit Breaker at the beginning of the circuit (within a few inches of the battery or terminal block). I would suggest that you NOT use a self resetting circuit breaker for obvious reasons.

Charging Systems are very different between cars and say boats. Cars are designed to recharge rapidly and then drop off shortly afterwards because of the fast discharge of the starting loads. Other Charging Systems are designed to charge at higher limits for extended periods of time making them much more efficient although at a much higher price. The alternator and wiring has to be much different to make it last with these higher outputs.
I am going to use a Regulator for the incoming power and before it gets to the battery or batteries (I am still in the physical restoration stages). This will ensure that I am not overcharging the batteries in the AS. The one that is at the top of the list right now is here;
Toad-Charge Towed Vehicle Battery Charger & Maintainer Kit - RV Power Supply
Do some measurements but the 40' version should work for most of us. This is designed to work with a motorhome and the toad (or towed vehicle) and that is how I found it but it (sure looks like what I want in my AS). I am setting up a 2005 Wrangler Rubicon to be towed by our 1981 Newell Motorhome (yes another riveted aluminum coach).

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