trailer battery wiring

[rfoubi]

So, a variation on the beaten to death dual battery setup. I have two batteries, main and house, connected by a blue seas ACR and charged off the alternator (and solar).

I also have a small travel trailer with two house batteries (well currently one but im installing another) that normally gets pulled with another vehicle, but will tow behind the van at times. I want to wire some heavy gauge wire to an anderson connector on the rear of the van to charge the trailer batteries off the vans alternator.

The question is, can i run straight off the alternator wiring, rather than running heavy cable all the way up front to the van batteries.

I'm curious as to whether the alternator will sense the batteries at the trailer and adjust voltage, or will it taper voltage as the vans batteries get full. (Alternator sense wire at the moment is at the main battery bank in the front of the van.)

Seems like running 4awg (or maybe 0,1) from the alternator to the rear sheetmetal by the licence plate, (fused of course) to an anderson connector, then to an isolator, then to the batteries on the trailer.

Is this crazy? Anyone done this? I want the capability to fully charge depleted trailer batteries in several hours driving, not just maintain or slowly trickle charge them like the normal 7 pin (10awg) 12v wire does.

Thoughts? Oh, its an EJ25 motor BTW

[crazyvwvanman]

How many amps is your alternator?
How many amp hours are your aux batteries in the trailer going to be?

You can make this work.
Yes, attach a wire to the alternator + post.
Run a negative cable from the alternator case.
Carry a known good spare alternator.
Don't make the cables too heavy and factor in the answers to my 2 first questions.

Mark

[IdahoDoug]

I just had to check this thread, to meet an optomist! If you tow with a vanagon that qualifies! Heh carry on.
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1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[PDXWesty]

I have to charge my trailer batteries before leaving on a trip. The wbx alternator just isn’t up to the task.

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89 Westy 2.1 Auto