7 pin plug question

[alia176]

I have a 7pin RV plug and was curious about the "trailer battery charge" wire/pin. What is the preferred method of providing power to this pin? This is for charging the deep cycle battery on the camper.

-fused +12vdc power direct from main battery
-fused +12vdc power from main battery switched from in cab (using a relay perhaps?)
-fused +12vdc power direct from second aux battery.

Thanks.

 

[D'Animal]

On our company trailers we wire it into the brake light. Everytime you touch the brake it is also charging the battery for the alarms system as well as the electric brakes.

 

[450 DUDE]

Im running a circut breaker from the main battery.
seems to work just fine.

ken

 

[BC_FJC]

Mine is direct to the main battery with a fuse... Just disconect the cable when at camp and have had no problems.

 

[alia176]

Im running a circut breaker from the main battery.
seems to work just fine.

ken

What size breaker are you using? Is it one of those 2 pin metallic thing that resets itself?

I am liking the idea of wiring to the aux battery (via switch/relay) so that both batteries can support the trailer while parked or I can separate the two if needed.

Thanks.

 

[Grim Reaper]

Put a relay on it so it cuts off with the key on the tow vehicle. That will prevent the trailer from dragging down the charge on the tow vehicle if something is using power in the trailer. Just the fact that the two batteries are different is going to cause a drain on one of the batteries if they are not activly charging. You want them seperated with the relay or an isolator if you do not use a relay.

For the run from the Tow vehicles battery to the plug use 8 gage since it is such a long run.

Most are fused at 30 amps. If it needs more then that then you need to use a external battery charger to bring it back up. Pulling up a dead battery is very rough on the alternator.

 

[alia176]

Excellent info, thanks!

 

[450 DUDE]

Im using an aircraft style 25A breaker, (push pull style)
It can be switched to your prefrence , Im rolling with a pop up so the only real draw is when the fridge is on 12v. I have never had any issue with drain but I do make an effort to switch the fridge when ever the stop time exceeds 1or 2 hrs.

ken

 

[John E Davies]

Since you already have a second battery up front, I suggest a marine battery select switch - it will allow you to select any number of batteries in various combinations, or all Off. I had such a system on a Suburban when I towed a travel trailer and it worked great.

http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/24867/377%20710/0/battery%20switches/Primary%20Search/mode%20matchallpartial/0/0?N=377%20710&Ne=0&Ntt=battery%20switches&Ntk=Primary%20Search&Ntx=mode%20matchallpartial&Nao=0&Ns=0&keyword=battery%20switches&isLTokenURL=true&storeNum=9&subdeptNum=null&classNum=0

These are "make before break" switches which are very important for the health of your alternator.

Cable size is also real important - use 12 AWG at a minimum, bigger is better for less voltage drop. 30 amp RV type breakers (self resetting) are fine for each battery charge wire.

Taking power off the truck's brake circuit is fine to recharge a little emergency "breakaway" battery, but it won't do squat if you have a big "house battery" back there for a water pump and lighting.

John Davies
Spokane WA