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Old 01-28-2016, 07:37 PM   #1
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Volts & Amps to trailer batteries

My TV is a 2008 3/4 ton Suburban. It has 40 amp fuse on trlr charge circuit. What volts & amps will the truck put into the 2 12 volt batts on my TT? I would think it should be near 40 amps sometimes. It doesnt charge the batts very well.

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Old 01-28-2016, 07:43 PM   #2
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It won't charge your camper battery well.
The wire size is to small and to long for much more then a trickle charge.

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Old 01-28-2016, 08:09 PM   #3
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The wire size from the fuse block to the 7 pin Bargman is relatively small, then add in the wire from the connector to the batteries. Even at highway speeds, you will have enough voltage loss that you will get little charging. As your vehicle is more than a few years old, it most likely does not have relay on the 12V aux line, That means if you stop for more than an hour or two with the TT connected and 12V appliances on, you could drain TV battery.

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Old 01-28-2016, 11:53 PM   #4
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Originally Posted by TURBS View Post
It won't charge your camper battery well.
The wire size is to small and to long for much more then a trickle charge.

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Old 01-29-2016, 01:40 AM   #5
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If you really are dependent on the tow vehicle charging the RVs battery, look into a device called a Trail Charger.

It takes a 12-volt input (throughout a normal voltage "range") and converts the charge voltage to 14.4 volts that will effectively charge the trailer's batteries. I suspect that they are usually at least a three-stage charger.

Trail chargers are made specifically for that kind of operation, especially if the distance from the alternator to the RV battery is quite a distance.

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Old 02-03-2016, 10:14 AM   #6
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I have been researching this subject also and don't have a definitive feel for how well our TT batteries will charge yet. We just bought it new back in November, but have not been able to do a shake down trip yet due to the weather here in Oregon.

I do know my 5 ton, 12' dump trailer which runs on one 12v battery to raise the bed will recharge given an hour or two of driving time. That's after a substantial discharge to make a dump cycle. That said, it has blown the 40a fuse on my 2004 GMC Sierra 3500 before when leaving the trailer plug in while cycling the lift pump. This tells me there is somewhere near 40 amps going to the trailer battery. (Now I unplug before a lift and reconnect for the drive out.)

I read elsewhere that using tow/haul on the older (2000's) GM's will increase the charge to the trailer along with using the headlights to kick up the amps. I do use the headlights as our dump site is on a highway the requires their daylight use, but only Tow/haul when loaded. We have made over 70 trips and it always recharges for the next go-round.

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