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Old 10-18-2015, 10:06 PM   #11
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Rule of thumb learned in electronics 101. "Current is constant in a series circuit." "Voltage us constant in a parallel circuit."

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Old 10-18-2015, 10:49 PM   #12
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Actually there is a lead acid battery made by Trojan that is even better than the 245 AH I mentioned. It is a GC2H, is 10.3 inches x 7.2 inches X 11.9 inches high, weighs 72 lbs and has a 20 hr rating of 260 AH. That has got to be an awesome battery.


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- 200 Watts Solar/MPPT Controller - 230 AH Battery Bank - 600 watt PSW Inverter - (2) 2000 watt Inverter Generators - LED Lighting - Boon Docking 99% of the time.
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Old 10-19-2015, 02:04 PM   #13
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We just installed 2 Costco golf cart batteries - 6V at 232AH each. Cost $150 for the pair. Fit perfectly in a box where 2 size 24 80AH 12V batteries had been jammed - a little taller, but I had the height clearance. Now have 116AH available (50% of 232) instead of 80 (50% of 160).

My previous size 24 12V batteries got mismatched for charge, and caused a fire in my battery box from the venting gases and the melting connecting wires (#6 wire). Had to cut the wires to put out the flames (small).

If parallel batteries get even slightly out of synch charge-wise, the curents can easily get to the wire melting stage. I much prefer the dual 6 volt series setup in a towed, land-based camper where a failure ends the camping trip (absolute worst case). I have 50% more capacity than I had, and the cost was quite reasonable.

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Old 10-19-2015, 02:10 PM   #14
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When I added solar to my 19RR I wanted to up the battery capacity. I agonized over it for weeks (I tend to do that....)...Anyways, I decided I wanted no maintenance so I wanted AMG. I used two 110AH group 31 AMG batteries for a total of 220AH and 110 usable AH.

My rational was price ($179 each at Sam's Club) and if one battery failed while on a trip I'd still have 12V available.
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Old 10-19-2015, 02:33 PM   #15
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The 12 vs 6 argument has been going on in solar and RV forums for years. The best argument that I have ever heard, besides all of the math examples, is actually quite simple. A 6V battery has 3 cells and a 12 V has six. When you look at a constant volume to put battery capacity in, 2 12 volt units means you have 12 cells, and all of the plastic separators required to support them. 2 6 volt units have only 6 cells and leaves more volume for plates and electrolyte. In fact, equivalent volume 6V units generally weigh more than 12, which is certainly due to lead! In lead acid batteries, weigh is good! In addition, series charging is more controllable since if batteries have different internal resistances they will still charge in a series configuration while the parallel setup that is required for 12v can be problematic. My 335DS has 6-12 volt house batteries since it has a residential frig, I would have preferred 6 volt units but will have to wait a few years to replace them.

Finally, if one battery in a 12V parallel circuit fails you will have significant trouble maintaining anything on the others without disconnecting the failed unit.

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Old 10-19-2015, 02:52 PM   #16
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Where were you Scott when I was agonizing!!!! That just makes perfect sense!

"For Sale...Two, like new AGM 12V batteries"

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