Another battery charging question - Fiberglass RV

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Old 09-28-2006, 08:22 PM   #1
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Trailer: 1998 13 ft Scamp
Posts: 26
I recently took my 13' Scamp camping in the Colorado mountains for the first time out longer than one night. I knew I would be running the heater, and not knowing how long the battery would last using lights and the heater blower, I decided to buy a second deep cycle battery, and have it as a backup. The new battery is larger, with a higher reserve capacity. I'm wondering if it would be better to mount both batteries on the tongue and wire them together in parallel, or use one by itself, then use the second one. The batteries would never be connected together in this scenario. Anyone have any experiences or expertise on this? I respect and value your input.

A second question: If I leave them seperate, is there any reason not to jumper them together while the trailer is in storage (inside), and let the smart charger maintain them together? In either scenario, I don't think the difference in capacity would matter.


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Old 09-28-2006, 09:35 PM   #2
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Trailer: 2005 13 ft Trillium Outback
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Do not wire them togther for use or charging.

The difference in capacity does matter. For best results only batteries of the same type, capacity, and age should be connected together. Dis-similar batteries will not share the load or charge appropriately.

Here are a couple links to give you some basic information The 12 Volt side of life
Batteries and other Electtical stuff


2005 Trillium Outback w/ 30" tongue extension
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1998 K2500 Chevy Silverado 6.5 Turbo Diesel, 4X4, ext cab, short bed
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Old 09-30-2006, 12:02 AM   #3
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Sonny, I'm no expert on batteries but I'm in the same situation as you are I had one battery [group 27] it wouldn't make it a week so I added another this time a [group 24] hooked them up together and now I have power that lastsI know up to 10 days at least that's what the last outing was. That also included running the furnace 4 nights. I plan on leaving them not hooked together over the winter just in case one of them fails that will keep it from dragging the other one down. I also have been charging them together and so far so good.
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Old 09-30-2006, 08:32 AM   #4
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Trailer: 2000 Burro 17 ft Widebody towed by Touareg TDI
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Sonny, I've always had two batteries hooked together. First they were not identical but it didn't seem to make a lot of difference. Now they are identical and therefore they appear to the charger as a single battery. Yesterday I came back from a camping trip and was able to test a new battery monitor, and for me it seems to take all the guesswork out of usage, charging, and how the batteries behave. I'd recommend it. It is essentially an ammeter with some electronic refinements which enable you to get a readout of how much is in the batterie(s), how much is taken out, and how much is put in. I wish I'd gotten one years ago. Expensive but well worth it. There are a number of decent ones out there (I chose a Xantrex Link 10). It will put an end to "Shut that light off, I don't know how much longer the juice will last us."
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Old 09-30-2006, 11:28 AM   #5
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Trailer: Fiber Stream
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I'm wondering if it would be better to mount both batteries on the tongue and wire them together in parallel, or use one by itself, then use the second one. The batteries would never be connected together in this scenario. [b]Anyone have any experiences or expertise on this?
My experience is a little different than yours, but I thought I'd share it here.

In my 16' Fiber Stream, I have added several features that require AC power. I also evenly split my camping time between "hook-up" sites and "boondock" sites.

When "boondocking" I have learned to forget the Air Conditioner, Microwave Oven, and the Automatic Drip Coffee-maker.

But, when camping during what passes for winter in Southern California, it mainly gets dark early, and I wanted to use my TV/VCR and my CD player in "boondock" sites. For that, I have a 300 watt inverter.

However, I have experienced battery failure during a camping trip. In my situation, loss of power to the water pump is even more critical than loss of lighting or loss of heater blower-motor function.

I do not want to jeopardize vital housekeeping functions by draining the house battery while watching a video. For this reason, I have 2 group 27 batteries, installed separately. My house battery runs the lights, water pump, and heater blower-motor, as the trailer was origionally designed.

My separate portable battery feeds the 300 watt inverter, mounted under the streetside bunk, with a DC power cord that feeds through the AC power cord hatch.

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It is also available as a back-up to the house battery.
Frederick - The Scaleman
1978 Fiber Stream 16 named "Eggstasy" & 1971 Compact Jr. named "Boomerang"
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Old 09-30-2006, 06:21 PM   #6
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Name: Gina D.
Trailer: '77 Leocraft 17 & Former Burro owner and fan!
West Coast USA
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I too, have two seperate battery systems. One for the "house" a group 24 that powers the lights, water pump and my 12v TV.

My DVD player is portable, as well as my fantastic fan. They run off two seperate 20ah gel cells. Both sets of banks are charged via solar, tho there is a charger on the house system for when I have AC.

If i do, fine, if not, my panels suit me needs well.

I have 12v outlets all over the trailer, mostly on the gel cells, for running non essentials if I want. Running down the house with non essentials is a bear.
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Old 09-30-2006, 06:45 PM   #7
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Trailer: Casita 17 ft 2004
Posts: 199
I have a question on something I thought about trying. I read all the info on the links suggested and it was great.
I have never boondocked in my egg and probably will not do it much at all. I currently do not carry a battery at all. I have a generator that runs AC and all my electric goodies but I only use it for short periods like at truck stops to cool off camper or make coffee or lunch.

What if I put a large good deep cell in the back of my truck, connected it to the old 12V wires the previous owner left on the front of camper? The wires go back to the egg's converter. I guess what I want to know is if the distance the "juice" travels the 12 or so feet to the converter from the battery, would it make it die quicker or hurt anything? This would be handy for having lights inside for short stops to rest.
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Old 09-30-2006, 08:07 PM   #8
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Name: Per
Trailer: 2000 Burro 17 ft Widebody towed by Touareg TDI
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Susan: My guess is that it would work fine, even though you might find the lights a shade dimmer than normal. Depends on the gauge of wire in your trailer. I'm changing out the charge wire and ground wire on mine from the 12 gauge (!) it came with to 6 gauge so that the charging is not so compromised with a lot of voltage drop. For lights the amperage would not be great, so you should be OK. No damage to the battery will happen (but put a fuse in there somewhere).
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Old 09-30-2006, 08:14 PM   #9
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Trailer: 1998 13 ft Scamp
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Thanks for all the replies. I welcome any more responses also. As usual, there are different experiences and opinions.

Susan, why not just install the battery on the trailer, same location as the original one. The problem with longer cables is voltage drop. With a load applied, you will not have full battery voltage available at the appliances when the battery is located further away. This is because of the added resistance in the longer cables. Same reason you don't want to use long extension cords when connecting to AC power. If you do mount the battery in the back of the truck, I would use larger gauge wire. My trailer has 12 ga., so I would at least go to 10 ga. to minimize voltage drop.

The idea of two batteries is an interesting one. If both are charged from the same converter, then I guess there is not a problem with one side "cross feeding" from the other side through the converter? Diodes probably.

The battery monitor seems like a good idea too. I want to keep this 13' scamp simple and lightweight, so I'll proceed slowly with adding new stuff. As far as staying with the lightweight goal, it might be better to carry the spare battery in the back of the truck, and change it over when needed. Decisions, decisions...

Thanks again to all!

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