Battery upgrade on my Bigfoot 21RB - Fiberglass RV


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Old 07-04-2019, 06:03 PM   #1
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Name: Jon
Trailer: Bigfoot
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Battery upgrade on my Bigfoot 21RB

I haven't done any off grid camping yet but just testing the battery in my driveway the battery hardly lasted at all running almost nothing. Few hours of leaving my fantastic fan on would just about drain it. So I wanted to do some good testing and got a 180 watt portable Zamp solar panel. I charged the battery 100% (12.71V) and disconnected the battery. The battery was at 12.6 the following day, a week later and it is at 12.43V. It has not been connected to anything since it was charged. I contacted the manufacturer of the battery (Centennial Deep Cycle DC24RVM non sealed Lead Acid) and it turns out this battery is 75ah. Kind of lame for a 21' Bigfoot. Not sure if that is how it was sold, and the first owners just ran on the grid, or if the first owners of the trailer had better batteries and used them in their new trailer so they threw this one in.



So now I need to decide if I'm going to upgrade to a set of sealed deep cycle AGM batteries, or just go full on with a lithium conversion like Jon Vermilye did here:


Converting to Lithium


I'm kind of a gadget geek so having lithium seems pretty neat, but I'm still not 100% convinced I'm going to keep the trailer. I love it but it seems just a bit too big. Towing it with my Colorado is ok but not super fantastic. Really I'm still getting use to towing so with some more practice I may find it's ok. Adding 2 decent AGM batteries is going to add a lot more weight than the lithiums, and I guess if I do end up selling it, having upgraded the batteries wouldn't be a loss since I could add it into the cost of the trailer right? Either way I go, I am pretty sure there is enough room for the batteries. There is a large area in the front under the cowl behind the propane tanks. 2 batteries should fit great there.



Mostly maybe I'm just venting I guess, much like my poor little 75ah lead acid battery.
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Old 07-04-2019, 06:11 PM   #2
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Name: Jim
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Quote:
Originally Posted by JonRaw View Post
I charged the battery 100% (12.71V) and disconnected the battery. The battery was at 12.6 the following day, a week later and it is at 12.43V. It has not been connected to anything since it was charged.
Sounds like a bad battery - should only lose a few percent a month disconnected.
There are 2 group 24 12V in parallel under the nosecone of my Bigfoot 17.
They last for days running fans/lights/water pump.
They last for ever with a 100w solar panel.

Jim
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Old 07-04-2019, 07:31 PM   #3
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I was going to convert my Oxygen to Lithium. I found a 2 pack of Lithium batteries at Amazon delivered for approx. $1500. The problem then is you need to convert your convertor for the lithium. A regular convertor can burn them up if you're not careful.

I do like the idea of going lithium as my new Hymer has a 12v compressor fridge. After I get it I'll check everything out and make the determination at a later date.

In your case I'd just upgrade the battery, use it for awhile, and then determine if you want to go through the expense and trouble. In my opinion very few future buyers would even know the difference in battery types and chances of recovering your investment would be slim.
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Old 07-04-2019, 09:44 PM   #4
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Trailer: Escape 21, behind an '02 F250 7.3 diesel tug
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if the batteries are mounted on the hitch, I'd consider upgrading to 2 x 6V GC2 golf cart batteries in series, this would get you like 220 AH give or take, which if you go by the max 50% discharge for best battery longevity, gets you 110AH usable, which is about 1300 watt*hours. I would go for wet cells for an RV application, as there's no risk of the battery tipping over or whatever, and a tongue mounted battery doesn't need special venting.
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Old 07-04-2019, 09:54 PM   #5
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Trailer: Black Series HQ19, Oliver LE2
Smith Valley, Nevada
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Losing a little voltage while sitting is not the same thing as very limited capacity. It sounds like your battery is sulfated. This will make it quick to charge up and reduce it's capacity, in some cases to near zero.

You can run a load test at an auto parts store to see if it has the rated capacity.

Good or not, one 75 AH battery is very small.

Since you are not sure if you want to keep the trailer, put (2) 12V Group 24, or better yet, (2) 12V Group 27 deep cycle flooded or maintenance free batteries, if they will fit. Or, as John suggested, get two 6V bats and wire them in series. I think I'd prefer the 12V batts in case one goes bad. Either setup will give you a significant increase in performance.

Be sure to keep the new ones charged to prevent them form getting sulfated.
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Old 07-04-2019, 10:11 PM   #6
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in general, the 6V golf cart batteries are true deep cycle, most 'marine/rv' batteries are not.
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