2 batteries on a Bigfoot trailer - Page 2 - Fiberglass RV


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Old 02-13-2019, 02:26 PM   #21
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Name: Mike
Trailer: 2005 Bigfoot 17.5'
Alberta
Posts: 23
There was a technical discussion a while back of the merits of 6v vs 12v, above my head mostly, but the concencus mostly was for the 6v pairing. Your point about losing one is a valid perhaps? Although a pair of 12's in parallel..if one went bad it would quickly bring down the other unless isolated. Good thought though, that hadn't considered .
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Old 02-13-2019, 02:42 PM   #22
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Name: dave
Trailer: scamp
New Mexico
Posts: 81
hmmmmm

Quote:
Originally Posted by Mike_L View Post
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.

I'm struggling to understand how with two 12V batteries wired in parallel, a drain on one managed to leave the other intact? And, of course your calculation of 2 x 220Ah 6v batteries in series would have the same power as two 110Ah 12v in parallel is correct but the difference to me is that 12V batteries are typically not true deep cycle, their plates are significantly thinner than in a 6v, and it's not common to find 12V batteries with a true 20h rating of 110Ah. Your mileage may vary.
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Old 02-13-2019, 03:14 PM   #23
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Name: Glenn ( second 'n' is silent )
Trailer: 2009 Escape 17B '08 RAV4 SPORT V6
British Columbia
Posts: 6,839
Trojan Battery has several deep cycle choices for you.
Google "Trojan battery maintenance" for answers to all your questions.
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Old 02-13-2019, 04:59 PM   #24
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Trailer: 2011 KZ Sportsmen 242SB / 2004 Ram-Cummins 2500 2wd
British Columbia
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Quote:
Originally Posted by semievolved View Post
I'm struggling to understand how with two 12V batteries wired in parallel, a drain on one managed to leave the other intact? And, of course your calculation of 2 x 220Ah 6v batteries in series would have the same power as two 110Ah 12v in parallel is correct but the difference to me is that 12V batteries are typically not true deep cycle, their plates are significantly thinner than in a 6v, and it's not common to find 12V batteries with a true 20h rating of 110Ah. Your mileage may vary.
My interpretation of his 'One drained, one intact' indicates he has an isolation switch, to guard against draining both batteries.
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Old 02-13-2019, 09:48 PM   #25
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Name: dave
Trailer: scamp
New Mexico
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Quote:
Originally Posted by Lloyd (aka Santa) Coltman View Post
My interpretation of his 'One drained, one intact' indicates he has an isolation switch, to guard against draining both batteries.

That makes sense and would work to safeguard one battery but then you don't really have 220Ah available for system use. When isolated, you'd have a 110Ah system for one purpose and a 110Ah system for all other needs and you really still have the risk that one or both could be run too far down. I suppose the same safety could be provided on either a 12V parallel or a 6V series system by including a low-voltage disconnect that leaves enough juice to take care of you.
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Old 02-14-2019, 09:50 AM   #26
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Name: Francois
Trailer: Bigfoot
British Columbia
Posts: 1,157
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"to learn all the different ways it can be done"

one "different" solution in a B17 is to put them under the right dinette seat like I did. Once I gave up on locating on the tonge (for a couple of reasons) I looked around and came to the conclusion that these trailers are heavy on the left side already and the area under the right dinette seat forward was sort of difficult to access/use anyway. The trade-off is lots of new outside storage space in the propane locker for landing gear, blocks, etc
I've been happy with the way it all works...no regrets.

(custom battery box screwed down to the floor, vented to outside)


I'm surprised some are rehashing the two 12V vs two 6V debate. I thought that one had been settled a long time ago! guess not
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