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RV-Auxilary battery charge?


ghixson's Avatar
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07-11-04, 06:28 AM   #1  
RV-Auxilary battery charge?

I have an old RV 1974 Midas which is basically a Chevy Van with the giant box on the back. All of the lights in the back living compartment, including the water pump, run off an aux battery that I have to charge up separately every other time I use the RV. (used only for Steeler Tailgate parties during season in Pgh)

Can I hook this battery up somehow, to be charged by the alternator that charges the battery up front with the engine? I know this thing is old (1974) but is there supposed to be system in place on this that maybe just had been unhooked by the previuos owner, where I might start? Should I simply start from scratch? Thanks!!

 
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07-11-04, 07:49 AM   #2  
'74........ OLD?.......It's only just broken in!

What would work for you is a battery isolator. They are relatively inexpensive.

It connects to your alternator.
You remove the main wire from the alternator and connect it to the marked terminal on the isolator. The alternator output then gets connected to its terminal. This leaves you with one remaining terminal to connect to the auxiliary battery.
This will then let the alternator then charge both batteries, but the diode in the isolator will then not let power from your main battery be drained when using the aux battery.

I have used one of these and they work well.

<img src="http://www.campingworld.com/ts-cwi/images/products/Normal/8000/8294A.JPG?wid=250&cvt=jpeg">
Image credit: campingworld.com


GregH.........HVAC/R Tech

 
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07-11-04, 08:48 AM   #3  
Thanks for the info, this sounds like exactly what i need.

 
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07-11-04, 09:20 AM   #4  
And then what happens to your main battery while your driving around using accessories with no alternator? That doesn't sound like too great a setup to me. Charging both at the same time would overload the alternator also. Why not do what we do with boats, hook up a solar trickle charger to keep it fully charged at all times?

 
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07-11-04, 10:21 AM   #5  
Desi,

Thanks. I should have pointed out the limitations of these isolators.

How this thing works is that it is just a simple diode.
It only allows current to pass in one direction.
The vehicle battery will work normally and the instructions show how the wiring will allow the alternator to power the vehicle when running.
As far as charging two batteries, you would have to use some common sense.
Yes, if both batteries were dead, the alternator could be overloaded but a lot of campers use two batteries in parallel and allow for this in the size of the alternator.
If ghixson had a small alternator he would have to be carefull to make sure to keep both batteries topped up and at least make sure the alternator doesn't try to charge two near dead batetries.

I've seen those solar chargers and I 've always thought they were to prevent the natural self draining that happens in lead acid batteries.
The one's I've seen have been less than a 1 amp charge rate. I am not sure if that charge rate would be able to charge a nearly drained battery in a reasonable enough time.

The use I made of these was to help maintain an auxiliary battery in a large one ton service vehicle.
I had a propane forced air furnace and lighting that required 12 volts to operate in my cube van with a 16' box.
During the week in sub-zero temps if I needed my tools and equipment to be warm in the morning I would let the furnace run overnight on the aux battery and the alternator would recharge it the next morning.
This worked well for two winters untill the price of propane went through the roof.
Actually, I didn't even disconnect the alternator wire and just hooked up the center tap to the battery terminal and the aux batt to the aux terminal.
Got 14.2 volts at the aux battery when the engine was running and my accessories didn't drain the truck battery, which is what it's supposed to do.


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07-11-04, 11:13 AM   #6  
Posted By: GregH I've seen those solar chargers and I 've always thought they were to prevent the natural self draining that happens in lead acid batteries.
The one's I've seen have been less than a 1 amp charge rate. I am not sure if that charge rate would be able to charge a nearly drained battery in a reasonable enough time.
.
I believe they make them a little larger now, like 3-5amps with regulator shut offs. They are basically to keep a battery fully charged when not in use, not for recharging a discharged battery quickly. They use them in marine applications for boats that aren't used much. I also see them hooked to batteries on navigation markers.

 
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07-11-04, 02:18 PM   #7  
Ya.
Come to think of it, there are some remote campgrounds around here that are nowhere near electricity and have radio phones with solar panels.


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