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Old 10-09-2011, 08:07 AM   #1
Hedonistic Bohemian
 
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Charging from alternator

When the TT is being towed, and the batteries are charging from the TV's alternator, I'm sure there's not a lot of amps involved because the wires in the harness aren't big enough to handle that.

My question is: What is limiting that current? What prevents us from melting wires and blowing fuses? (I know, that's two or three questions.)

If I hooked jumper cables from the TV batteries to the TT batteries and ran the TV, would that be the same thing? (I know, another question.)
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Old 10-09-2011, 08:34 AM   #2
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this thread can help with some questions/answers:
http://www.airforums.com/forums/f449...cle-60090.html
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Old 10-09-2011, 10:20 AM   #3
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Quote:
Originally Posted by Bohemian View Post
When the TT is being towed, and the batteries are charging from the TV's alternator, I'm sure there's not a lot of amps involved because the wires in the harness aren't big enough to handle that.

My question is: What is limiting that current? What prevents us from melting wires and blowing fuses? (I know, that's two or three questions.)
Wire length, size and resistance of the connector, from the front of the TV to the batteries somewhere in the AS will limit the tow charge current flow to from 5 to 12 amps in my experience. I have a digital ammeter with shunt on my Argosy 20' and that allows me to see just what charge current I get.

You can put a much larger wire in the TV, and better connector, and larger charge wire in the AS to get more tow vehicle charge to the AS batteries, but it is a royal PITA to do, and every time you change TV's you have to go through it again.

A good Converter/charger such as a Progressive Dynamics 9245 or 9260 and a generator will do the job better, faster, and easier. I still like some charge from the TV, but have resigned myself to it's limits.
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Old 10-09-2011, 10:29 AM   #4
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I like this forum!!
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Old 10-09-2011, 11:38 AM   #5
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I used to own a TT trailer with a 3 way refer. Until I put a much larger guage wire in the TV, the battery in the TT would go dead from running the refer on 12 volts on an all day drive. I was happy when our our next TT had only a 2 way refer. I no longer have to wrestle with the feeling that I shouldn't run the refer on gas while traveling for "safety".

Ken
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Old 10-10-2011, 08:32 AM   #6
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From what I read in the referenced thread, resistance in the wiring is the current limiting device. That's why it can charge the TT batteries at 6 amps or 12 amps but it prevents that from going to 30 or 45 amps, which would melt or blow something.

I guess that's true, but it hardly sounds like something the automotive engineers at Ford would do.

After reading more I guess there is a battery isolator built in to the TV, though the alternator's output is regulated by the needs of the TV's batteries and the voltage the TT sees is whatever happens to result from the conditions.

In my application I have two AGM batteries in the truck bed and an inverter/charger which I can plug into the wall. I plan to install a solar panel on the truck to reduce the need to plug in. Using the truck to charge will be a backup when solar can't keep up and plug-in isn't available.

For now I think I will just rig something up to charge off the hitch connector, which will be low and slow but something.

Thanks for the advice.
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