BFL13 wrote:
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EDIT--BTW I have posted details of using an inverter on the truck battery to run a battery charger where you can have long 120v wire and short fat 12v wire. You do hit a limit on charger amps out when the truck voltage starts to fall off from 14ish. That tells you what you can do. Of course the inverter has to be big enough to run that battery charger. It does work. BTDT. (See posts from 2011 when I did that and reported here how it went) Only good for when parked of course, no good while driving around :)
That's what I'm doing, even when driving around.
In my case, the distance isn't too far from the alternator to the trailer batteries, maybe 20ft, so a DC only solution (big-wire and/or up-convert to higher DC voltage) would have been doable.
But by up-converting to 120VAC you have the option of charging your trailer batteries with something more sophisticated than simple alternator voltage. With temperature compensation and adjustable Absorb V for example.
In sequence my rig has:
220A alternator
60A fuse and battery isolator
1000W inverter in truck
120VAC 12awg extension cord to trailer split by waterproof plug/socket
120VAC 500-700W charger in trailer
Works well.
On my RAM's 220A alternator the V's are rather constant 14.3-14.5V but have heard that they will increase up to 15V in very cold weather.
