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Old 09-08-2013, 12:31 PM   #1
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Second Battery in TV

I have a 2011 Chevy 2500 with a factory tow package. It has the 7 pin and the brake controler built in. It does not have a second battery.

I plan to spend s couple months hopping around National Forest campgrounds next summer and I was thinking a battery in the truck that was dedicated to the camper might be a good idea, but I don't know how they work.

1) Is the second battery isolated from the starting battery when the motor is off?

2) Is the second battery connected to the Hot Wire in the 7 pin when the motor is off?

3) If I have the batteries in the trailer turned off using the little switch by the door, will the 12V system in the trailer work off the 7-pin? Allowing me to save the two batteries in the camper for when the truck is missing.

4) When I am driving, ss the charging system in a modern truck able to deal with two batteries in the camper, and two in the truck?

Thanks in advance
Brad
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Old 09-08-2013, 02:15 PM   #2
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Brad, I think the answer for 1, 2 and 3 is, it will be what you want it to be when you have the second battery installed. Specify what you need when you have the battery installed.

On 4, I suspect it is, but check with a Chevy dealer.

On the other hand, have you considered a solar system. They keep the AS batteries topped off just fine. Depending on your negotiating skills, and the local market, it might be less than what you're proposing on your truck.
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Old 09-08-2013, 02:32 PM   #3
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There are many ways to wire a second battery in your TV, and what is done will determine the answers to your questions 1, 2 and 3. The charging system in most modern pickup trucks will deal with any number of batteries most likely, that is not a real concern.

I second Drathaar's comments about a decent solar system. I installed a good 200 watt one on my new 20' FC for about $700 using my own labor.
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Old 09-08-2013, 02:50 PM   #4
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While I agree with those guys that you can pay to have it wired any way you want, I doubt the cost is trivial. The 12 v connection on your GM pickup is hot all of the time unless you change the wiring or install a relay. The batteries in your AS are disconnected from everything except factory solar when you go to Store mode, unless you change that wiring. I have no idea what the alternator rating is, if it can handle 4 depleted batteries. All good questions.
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Old 09-08-2013, 03:03 PM   #5
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Quote:
Originally Posted by lsbrodsky View Post
.... stuff clipped...... The batteries in your AS are disconnected from everything except factory solar when you go to Store mode, unless you change that wiring...
Larry
They are disconnected from other charging sources, and from the main DC buss, but there is still a phantom load (gas leak detector, etc.) on the batteries. That's why solar is so beneficial, it compensates for that load.
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Old 09-08-2013, 04:17 PM   #6
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Quote:
Originally Posted by Bbelk View Post
I plan to spend s couple months hopping around National Forest campgrounds next summer and I was thinking a battery in the truck that was dedicated to the camper might be a good idea, but I don't know how they work.
Not sure what you hope to accomplish by putting an extra battery in your truck....your money would be better spent on a cheap small lightweight generator to recharge the battery in your camper.
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Old 09-08-2013, 04:30 PM   #7
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Some thoughts re your questions....

1. It depends on how you install the 2nd battery wiring - normally, a constant-duty relay is installed. A minimum 4 AWG cable is then routed - from battery #1 - thru the relay that's activated only when the engine is running - to battery #2. This insures that batt# 1 (starting battery) is isolated from battery #2 when ignition is OFF to insure it won't be discharged from an external source...

2. Normally, the pin 7 'HOT' wire is NOT connected the TV's battery when the ignition is OFF and is wired thru a relay - Again, to insure your starting battery isn't discharged by anything hooked to pin 7 (your trailer)...

3. Don't know how that trailer ON-OFF switch is wired in relation to the pin 7 hot wire from the tow harness...somewhat confused by your comment, "truck is missing" - if the truck isn't hooked up, the pin 7 doesn't even come into play...???

4. In many cases, a larger capacity alternator is installed with the factory tow package, but don't know in your particular case... Due to the wiring size most often used in the pin 7 circuit, you only get marginal charging voltage all the way back to the trailer...If your trailer batteries are discharged fully, it could take many, many hours for the pin 7 circuit to recharge them...

If you are adding a 2nd battery in the TV to be used by the trailer for additional capacity when camped, you'll probably have to run dedicated cables (both POS & NEG) from the 2nd battery directly to the trailer batteries...

A 2nd TV battery is usually installed in van type campers (MoHo's) and sometimes for truck campers, but don't offer any real advantages for towable RV's due to the wiring issues I mentioned above...

Happy Trails...
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Old 09-08-2013, 05:58 PM   #8
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Quote:
Originally Posted by Drathaar View Post
They are disconnected from other charging sources, and from the main DC buss, but there is still a phantom load (gas leak detector, etc.) on the batteries. That's why solar is so beneficial, it compensates for that load.
My curiosity got the better of me and I had to go look. Sure enough the little green light on the gas detector is flashing and there is no mention of a separate battery for it. Airstream didn't mind separate batteries for the water filter, the doorbell and the CO detector, so I wonder why the gas detector runs off the batteries and why the memory in the radio does not.

Quote:
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Not sure what you hope to accomplish by putting an extra battery in your truck....your money would be better spent on a cheap small lightweight generator to recharge the battery in your camper.
The idea was that I would probably be driving the truck around some and thus charging the battery that I could use to run the fans through the night and saving the trailer batteries for powering the brains in the fridge and water heater.


Quote:
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3. Don't know how that trailer ON-OFF switch is wired in relation to the pin 7 hot wire from the tow harness...somewhat confused by your comment, "truck is missing" - if the truck isn't hooked up, the pin 7 doesn't even come into play...???
I guess that was poorly worded. The intent was that I was thinking I would take the trailer batteries off line by using the STORE button to disconnect them when the truck is plugged in. When the truck leaves, I would turn the trailer batteries back on to keep things like the refrigerator working.
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Old 09-08-2013, 06:08 PM   #9
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Brad, I'm an advocate of the KISS principle. (Keep It Simple & Stupid) To my way of thinking, you're making things pretty complicated. Solar and perhaps larger batteries would accomplish what you want to do, without a degree of complexity!

You may (?) be able to get group 27s, 29s or 31s in the box on the Classic.
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Old 09-08-2013, 07:42 PM   #10
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My buddy uses one of these to charge his batteries when camping (I bought the next model up with a 4 stroke motor) both of ours are going on two years old and so far have operated flawlessly. Although mine is small and light weight if I had to do it over again I'd probably buy the smaller and lighter two stroke model.

http://www.summitracing.com/parts/xyz-cm04101
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Old 09-09-2013, 02:31 PM   #11
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2nd battery installation in my pickup:

http://www.airforums.com/forums/f417...1-a-88508.html

I did the same mod in my 2004 'burb.

Plan on $200 plus the cost of the battery by the time you pay for the isolator and the battery cables.
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Old 09-09-2013, 05:43 PM   #12
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I installed a 7 pin receptacle in the side of the coach near the battery location. This plug only has the charge line and common/ground terminals wired.
Since my coach only has one (house) battery and no convenient place to house a second battery close to the original.
I carry the second battery in the box of the TV. When I am not towing, I can connect this battery to the trailer plug of the TV. It will charge as I drive.
I also have a portable solar panel. I use it to charge the house battery thru the receptacle mentioned above. Or I can connect it to the second battery and keep it charged while in the truck. I can also plug the second battery into the coach then connect the solar panel and charge both the house and second battery.
We have boondocked for more than a week with no problems.
The receptacle on the coach also provides a 12 volt power source on the exterior of the unit. Should I need to run an air compressor or pump etc.
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