2 batteries on a Bigfoot trailer - Fiberglass RV


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Old 02-04-2019, 11:18 AM   #1
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2 batteries on a Bigfoot trailer

I am contemplating replacing the single 12-v battery on my 1995 Bigfoot 16G trailer with two 6-v deep cycle marine batteries wired in series. I wonder if anyone has any experience with fitting 2 batteries under the fiberglass cover on a trailer of that vintage.
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Old 02-04-2019, 11:38 AM   #2
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I have the same camper (1991) and I'll also be doing this pretty soon. I remember someone here has...we'll see if they chime in. I think fabricating a tray to fit them won't be as much an issue as the fiberglass cover, but I haven't taken any measurements yet. I don't think they fit on the current tray between the frame, though. I just think that's an easier problem to solve than the cover, as you've obviously figured out.

If no one gets to it before me, I'll post my process. Won't be till things thaw out though.
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Old 02-05-2019, 07:15 AM   #3
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Hi Robert,
Search "Bigfoot battery upgrade" for a terrific demonstration of what you have in mind. Can't seen to link to it directly.
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Old 02-05-2019, 08:59 AM   #4
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Originally Posted by Tony Nowak View Post
Hi Robert,
Search "Bigfoot battery upgrade" for a terrific demonstration of what you have in mind. Can't seen to link to it directly.
Tony
I think you're looking for this:
wheels for My trailer

Despite displaying "wheels for my trailer," it is in fact a battery upgrade thread.
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Old 02-05-2019, 09:48 AM   #5
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Quote:
Originally Posted by bobblangley View Post
I am contemplating replacing the single 12-v battery on my 1995 Bigfoot 16G trailer with two 6-v deep cycle marine batteries wired in series. I wonder if anyone has any experience with fitting 2 batteries under the fiberglass cover on a trailer of that vintage.
I'm about to add two large AGM batteries and associated matching charging equipment to my 2006 25B21RB. After much research I've decided to forgo any modifications to the trailer's frame or the fiberglass cowling housing the propane tanks and factory battery tray. While the very elegant modification described in this thread: wheels for My trailer looks fabulous and undoubtedly functions perfectly it no doubt was a labor-intensive fix.

For my purposes, based on the configuration of my trailer, the solution settled upon will be to place the AGM batteries on their sides under the couch, close to the power center. Unlike lead acid batteries AGM batteries can safely lay on their side. As well, concerns about battery outgassing are negligible making them safe to mount in a frame inside the trailer.

I don't know if there is enough room inside your trailer to do something similar but I wonder if two tall 6V batteries can be wiggled into such a small space. On that note I gave some thought to removing the FG shroud and placing my tall AGM batteries inside a large battery box mounted onto a slightly modified battery tray. With that arrangement I thought a standard plastic propane tank cover could be an adequate substitute for the factory FG shroud.

Others likely have other solutions.
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Old 02-05-2019, 10:31 AM   #6
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That brings up a point I hadn't thought of, which is the increased tongue weight. I'm already pushing the payload limit of my truck.
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Old 02-05-2019, 12:18 PM   #7
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Sorry, I can't offer much help with this. My trailer came with one battery but space for two. No cover, the batteries are housed in separate battery boxes. These battery boxes are readily available and easy to install.

I've tried both the two 6 volt batteries wired in series and the two 12 volt batteries wired in parallel arrangements and found little difference in performance.
As an example, two 220 amp/hr 6 volt batteries wired in series yields 220 amp/hr of 12 volt power.
Two 110 amp/hr 12 volt batteries wired in parallel also yields 220 amp/hr of 12 volt power.
The 6 volt batteries must be evenly matched. If one fails, both have to be replaced.
The 12 volt batteries can be used separately. If one fails, the other one is still usable so you only have to replace one.
I used both for 7 plus years before their performance dropped.

I recall a situation where the breakaway switch on my trailer was "accidentally" activated. I awoke the next morning to my "low battery" alarm as the single 12 volt battery I was using had been discharged by the electric brake being activated all night.
Had I been using two 6 volt batteries in series (or both 12 volt batteries in parallel) I would have had no power, not good for boondocking in the back country.
Using one 12 volt battery, I had the other one to use while my solar panels recharged the other one. This was the deciding factor for me.
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Old 02-05-2019, 12:21 PM   #8
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In the thread referenced above showing the modification, the owner said he had to swap 2-30# propane tanks for 2-20# tanks. I've been considering taking out one of my propane tanks to make room for an extra battery.

I have an 8' bed with a shell in my tow rig and I carry a very small propane tank for a camp stove anyway that could tide me over if the larger tank on the trailer runs out. That would also not lead to greater tongue weight.
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Old 02-05-2019, 12:22 PM   #9
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In the thread referenced above showing the modification, the owner said he had to swap 2-30# propane tanks for 2-20# tanks. I've been considering taking out one of my propane tanks to make room for an extra battery.

I think 30# propane is adequate but I would lose the flexibility of switching from one tank to another.

I have an 8' bed with a shell in my tow rig and I carry a very small propane tank for a camp stove anyway that could tide me over if the larger tank on the trailer runs out. That would also not lead to greater tongue weight.
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Old 02-05-2019, 12:46 PM   #10
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Originally Posted by bobblangley View Post
In the thread referenced above showing the modification, the owner said he had to swap 2-30# propane tanks for 2-20# tanks. I've been considering taking out one of my propane tanks to make room for an extra battery.

I think 30# propane is adequate but I would lose the flexibility of switching from one tank to another.

I have an 8' bed with a shell in my tow rig and I carry a very small propane tank for a camp stove anyway that could tide me over if the larger tank on the trailer runs out. That would also not lead to greater tongue weight.

Your comment triggered a thought and also gave me an idea: Keep one 30 lb bottle and build a platform next to it that an extra battery sits under. A smaller 20lb bottle would sit on top of the platform. That way the pigtail connecting the two propane bottles would still be useful; with such an arrangement two batteries could still be connected together. I'm looking for my measuring tape...

Comments???
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Old 02-06-2019, 09:38 PM   #11
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Originally Posted by bobblangley View Post
I am contemplating replacing the single 12-v battery on my 1995 Bigfoot 16G trailer with two 6-v deep cycle marine batteries wired in series. I wonder if anyone has any experience with fitting 2 batteries under the fiberglass cover on a trailer of that vintage.
I have a 2002 17' CB and it came with 2 group 24 12v batteries and 2 20# propane tanks. They fit fine under the cover.....
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Old 02-07-2019, 08:59 AM   #12
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I wonder how much they changed things between mine and yours. I'll have to measure, but my one battery seems to be a fairly snug fit in the tray. Hard to believe I'd fit another battery in there. Never checked the amount of clearance to the cover but I'll do that too. It was practically spring here a week ago...dry ground and temps in the 30s and 40s. This morning it's -18F and 6" of snow on the ground...that's a good thing, but I won't be doing anything to my camper (other than shoveling off the roof) anytime soon.

Someone here either did their own or posted someone else's test on 12V vs 6V. I'm no expert and though this isn't like some topics...it still seems be a debated one.

Anyway the test showed that two 6v batteries do perform better overall than two 12V. But in the end, it seems to come down to how likely you think it is that one battery will fail (determined mostly, I'd guess, by whether you've actually had his happen to you in the past or not), and how much of an inconvenience you think it'll be to replace a 6V on the road.

Maybe this is a topic for another place, but what's the setup that allows the use of two 12V batteries separately? And the ability to charge one while the other is in use?

I'm researching a system upgrade, doing the work to determine how much power I want to be able to use, and match a solar panel and battery bank to that use. So I'm especially interested in all the options right now...

I've got a portable 95W panel and one 12V battery (don't know the ah off the top of my head). This has worked fine for me for 3 years, but my job doesn't require me to come in to the office, and I'm still living in the camper most of the year. I'd like to be able to work from "home" more, but I've been limited by my ability to charge a laptop. So I'm looking to upgrade a bit.
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Old 02-07-2019, 10:14 AM   #13
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Maybe this is a topic for another place, but what's the setup that allows the use of two 12V batteries separately? And the ability to charge one while the other is in use?
I'd guess someone else will be around who has actually done this, but here's a starting point: https://www.westmarine.com/WestAdvis...Second-Battery. Scroll down to the bottom and there is some info about a battery switch and charge management. They link to this product specifically: https://www.westmarine.com/buy/blue-...ystem--8646275. That may not be the ideal kit for charging an isolated battery from solar, though, as it intended to isolate a boat's starting batteries from house batteries, allowing use of the house batteries in an emergency.

Maybe the "old school" switch in that article is a better option for trailers? You can select bank 1, bank 2, both, or none. I think you'd need one from the batteries to the trailer and another one from the batteries to the charger. That would be a low tech solution; there must be smart electrical management systems and battery monitors out there that can isolate your batteries for use/charging as needed.

When we find our dream trailer, I had planned to switch to dual 6V batteries. Now I'm rethinking that as I rather like the idea of having a redundant 12V power source for when somebody leaves a light on overnight.
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Old 02-07-2019, 10:28 AM   #14
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It's definitely tempting to do it the easiest way and just get a decent sized battery or two, 100W of solar, and go on my way. And I'd say most people can get away with that. But it's also tempting to learn all the different ways it can be done, think really hard about how I'll specifically use my trailer and go with what will work best for me.

I'll probably end up doing something in-between the two...I'm willing to do some research work, but there's only so much time to become an expert in so many things...
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