Camper Trailer Battery Charging

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sknubel

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Oct 10, 2012
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So I have a 1989 Terry Resort trailer.  I bought a new battery for it.  When I plug AC power in to the trailer, it charges the battery (the power meter in the trailer reads charge).  So that seems to be working fine.

My question is regarding charging off of my truck.

I have a 2012 Toyota Tundra with towing package, 7 pin harness adapter.  When I plug the trailer into the truck, with the truck running, the lights and everything in the trailer works, but I don't think it is charging the battery.  The meter reads battery weak, and not charge.  I guess I was expecting it to say it was charging when the truck is running.

Insights please??? Should the battery be charging off of the truck???

Thanks, Stephan
 

Frizlefrak

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Yes it should.  Check for voltage using the diagram below.  If you have voltage at the plug, trace the wiring in the trailer. 



 

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berky

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Make sure there's a fuse in every slot designated for "Trailer" in the Tundra fuse box.  There might be as many as 3 fuses - running lights, brakes, and battery.  There should be a diagram of the fuse box with fuse sizes in your owner's manual.
 

sknubel

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Oct 10, 2012
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I talked to a guy at the trailer shop today....he said since the trailer is pulling power from the truck (rememebr all of the interior trailer lights work when plugged into the truck), he thinks it is just a slow trickle charge meant to maintain the trtailer battery over the road.

What do you think??
 

berky

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A quick web search says the Tundra's alternator is rated somewhere in the range of 130 A - 150 A.  How much of that actually flows to the trailer battery depends on the the condition of the TV battery, the condition of the TT battery, what accessories are running (lights, heater fan, etc.), wire size and length, etc.

I'm guessing you might find 10 A - 20 A flowing to the TT battery.  More than a trickle, but not enough to fully charge a battery over the course of a 1-2 hr. drive.
 

Gary RV_Wizard

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Your trailer interior lights should work whether plugged into the truck or not - that's what the trailer battery is for. So, having lights when plugged to the truck proves nothing. You need to check battery voltage to determine if the truck is supplying any power via the plug.  The battery voltage should stay above 13.0 (preferably 13.3-13.7v) when the truck is running, even with trailer lights on. Use a voltmeter rather than the trailer's battery display - it will give you a much better picture of what is going on.

If the voltage is not above 13, next check voltage at the trailer plug on the truck, using the diagram above.
 

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