Battery ignorance - Fiberglass RV

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Old 07-11-2009, 09:06 PM   #1
Junior Member
Fabienne M.'s Avatar
Trailer: Trillium 4500 1977
Posts: 4
Hello all!
Have been having the best time with our Trillium 4500 (1977 model) for the past two years. Till now we had always justed plugged ourselves in at camping sites and voilą! There was light! Suddenly we got this urge for a battery thinking "hey! Great! If we want to set up somewhere where there isn't any electricity available at least we'll have lights!" Bought a good deep cycle battery plugged it in and off we went. Thought it was suppose to recharge from being hooked up to the car when we drove between sights but apparently my lack of knowledge in this field has definitely caught up to me cause my battery is now dead! Anybody out there know what the problem is? Can anyone suggest a good website for tutorials because I'd really like to understand how this thing is supposed to work. Ignorance isn't bliss at all.

Thanks everyone!

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Old 07-11-2009, 09:29 PM   #2
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Booker B.'s Avatar
Trailer: 1976 Trillium 13 ft
Posts: 983
Hi Fabienne,

There are a lot of different approaches you can take to 'dry camping' on a battery. Depending on how YOU camp here are a few options in what I feel are best to worst options IMHO.

1. Installing a 3 step charger (converter) in your trailer that both charges your battery and provides 120v when you are plugged in (what I have done). Conveniet but expensive.

2. Purchase a 3 step battery charger that you charge your battery with by hooking up when you have 120v. Proabably the best bang for your buck.

3. Charge battery from solar power - this is a great setup for topping up your battery while camping if you use either of the above. Expensive and will require some time to optimize.

4. Charge battery from your vehicle - generally you will not get a lot of charging power from your car from what I understand.

You will be getting a lot of opinions on this so it really depends on what works for you.

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Old 07-11-2009, 10:21 PM   #3
Don H.'s Avatar
Name: Don
Trailer: Compact Hunter I
Posts: 70

I suggest you go to a trailer shop - one that works mainly on horse- and/or utility trailers, NOT an RV shop. They'll be able to make sure you have a charge connection, and importantly, a battery isolator, which allows your alternator to charge the house battery, and also ensures that your Tow Vehicle's battery is not connected to the trailer battery at any time (bad news for both batteries...).

If you currently have a 4-prong connector, then for sure, you don't have a charge line.

I vaguely remember seeing some tutorials on the web regarding all kinds of trailer maintenance, but just about all of my bookmarks are out of date. I'm sure you can find some via Google.

Also, I highly recommend a book called "Managing 12 Volts: How to Upgrade, Operate, and Troubleshoot 12 Volt Electrical Systems" (Paperback) by Harold Barre, for anyone who has a trailer or RV with house batteries. It looks like it may be out of print, but I do see used copies on Amazon.
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Old 07-12-2009, 11:50 AM   #4
ddayton's Avatar
Trailer: 2007 Casita 17 ft Spirit Deluxe
Posts: 84
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Fabienne - here is a site with lots of 12v & battery info.

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Old 07-13-2009, 12:14 AM   #5
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Name: Bruce
Trailer: Bigfoot 25 ft RQ
Posts: 351
Hi Fabienne,

Your post brought back memories. I had a similar experience. I purchased a brand new trailer and started out on a trip to Alaska. About night three the battery was dead. I was still on the steep part of my learning curve about travel trailers and that caused some anxiety. It cost $173 (Canadian) for me to get an RV mechanic to run down the problem. A charging wire had been left disconnected during the manufacturing process of the trailer. A couple of years later I replaced the battery with a brand new battery. I two days later I had a dead battery. That time the charging system was fine it was the new battery that was defective. I now know quite a bit about trailer wiring.

I am not familiar with how your particular model trailer is set up. It may or may not be wired for the trailer battery to charge from the tow vehicle. You will need to find that out. If it is not it can be wired to do so.

Late model tow vehicles with factory trailer wiring harness will have a "hot post" in the plug that provides a charge from the vehicle's charging system to the trailer system. The tow vehicle owner's manual may even have a diagram that shows which one it is. If your vehicle does not have the trailer charging circuit it can be added.

That works pretty well if you are on a cross country trip and towing the trailer a few hours each day. Where you run into problems with that system is when you camp more than a day or two and don't run your vehicle or otherwise charge the trailer battery.

Don is correct, you need to make sure your trailer system is isolated or not drawing from your vehicle battery when you are parked and your vehicle is not running. Otherwise, overnight it can run your vehicle battery down and it won't start the next morning. More than one camper has fallen into that trap. I had 2003 and 2007 Ford trucks with factory trailer wiring that isolated the trailer system when I shut the truck off. However I had a new 2006 Chevrolet with a factory trailer wiring that did not. I had to unplug the trailer when I stopped for the night.

I wound up buying a high accuracy ac/dc multimeter:

I can now quickly and easily evaluate an entire electrical system. It will measure voltage down to 1/10<sup>th</sup> volt and current to a fraction of an amp. I can quickly tell if a battery is charging and how many amps it is receiving. I can also measure amperage flow or current draw through individual wires. You can figure out just how much electricity each item on your electrical system is producing or using. It will even test 1.4 volt watch batteries. I highly recommend that every FGRV member get one or one similar and also read up on RV and automotive electrical systems. It will save a lot of anxiety and cost.

The high accuracy at low volt and amp ac/dc instruments that will measure down to 1/10<sup>th</sup> volt or amp are hard to find in stores. You need to order from the internet.

I will attach a picture of mine testing the voltage of a 6 volt tractor battery.


Bruce H

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Old 07-13-2009, 09:11 AM   #6
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Name: Per
Trailer: 2000 Burro 17 ft Widebody towed by Touareg TDI
Posts: 863
You have gotten some good advice here. Since I was determined to solve the problem of not getting much "charge" from the tow vehicle I took the following steps: Changed the charge lines from the tow vehicle battery/alternator all the way to the batteries in the trailer to 6 gauge wire and added a switchable continuous duty relay to the circuit (works great, much cheaper and less voltage loss than an isolator).
The electrical experts told me that hefty charge and ground wires were crucial, since a very small voltage loss can have a dramatic effect on the ability to charge from the tow vehicle. 14 or 16 gauge wires are unlikely to do the job. Problem solved.
I did add a "battery minder" which tells me exactly what is going on, including what the voltage is, how much juice is left, the intantaneous rate of charge or discharge, etc. As a result I get no surprises, and it is easy to diagnose problems. But, as others have pointed out, the bottom line is the heft and condition of the charge wires.
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Old 07-14-2009, 03:13 PM   #7
Trailer: 2011 KZ Sportsmen 242SB / 2004 Ram-Cummins 2500 2wd
Posts: 68
If you go here, and read

<div align="center">The 12 Volt Side of Life</div><div align="center">Deep Cycle Battery FAQ<a href="" target="_blank"> </div>
</a>You will find a wealth of info about 12V battery systems. I bought a Xantrex XADC40 from him, and I love it, no more boiled dry, or undercharged batteries (a major concern, as I use a 12v CPAP machine to overcome 'Sleep Apnea'). BTW, my tow vehicle came with #10 wiring for charge and ground, and I've never had a problem. But, my batteries are always at full charge when I leave home, and in top shape, because of the three stage charging at home.
Note: vehicles charge at 14.5-14.8V, while the ideal for long life on deep-cycles is 13.5-13.8V. Don't fret it too much, the relatively short duration of vehicle charging won't harm them, but long term, higher volt charging will cook them. Somebody made a comment about 4 pin connector vs 6 or 7 pin. Definitely, if its 4 pin, there'll be NO charge circuit, and the wiring will probably be #18, barely heavy enough to carry the lighting current. Do you have DC(12V) lighting, or a mix of 12 and 115v?

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