Montana Owners Club - Keystone Montana 5th Wheel Forum - View Single Post - Adding 2 6 Volt Batteries to existing 12 Volt

Art-n-Marge · 12-20-2011, 06:36 AM

I wish I could find the articles, but I've read several times it is not good to mix voltages and battery types for concurrent use. Electrically speaking the voltages are not the issue. The issues start with the characteristics of the batteries in that they often have different discharge and charging rates and this is where the problems start. For example, do not mix, gel with water, maintenance-free with maintenance type, dual 6 volt with 12 volt. This can cause a faster discharging water-filled battery to draw down a slower discharging gel-filled. I believe the advantage to 6V batteries is that they discharge slow and recharge quicker than most 12v, therefore having a 12v in the concurrent circuit would negatively impact the 6v batteries.

Some above have mentioned that they have both type inline but they are isolated, so this satisfies the principal of keeping them separate.

I experienced the "different attributes" battery issue first hand when I had TWO water-filled batteries and they were the same brand and model, but when one battery was failing (after 5 years of ownership) it caused the other one to seem it was failing too (I could never read higher than 13.2v even when charging). When I finally got smart enough to isolate each battery from each other, and found that the failing battery no longer recharged (remained around 11v) then the other battery perked up to over 14 volts when recharging and about 13v when operating and the single batter kept the trailer operating correctly. You can imagine how much worse it could have been even with good batteries, the one that has worse characteristics can cause the better battery(ies) to have degraded performance.

I wouldn't connect dual 6v with 12v because I think this would be the biggest difference between 12v systems when it comes to different characteristics. But to answer your question having two switchable separate systems like what was mentioned above would work, but then one system is dead weight while the other is doing its job. But maybe when the one starts to discharge too much and you switch to the other provides redundancy.

Let us know what you do. Many owners have some very creative setups.

12-20-2011, 06:36 AM	#7
Art-n-Marge Montana Master Join Date: Apr 2009 Location: Murrieta Posts: 5,816 M.O.C. #9257	I wish I could find the articles, but I've read several times it is not good to mix voltages and battery types for concurrent use. Electrically speaking the voltages are not the issue. The issues start with the characteristics of the batteries in that they often have different discharge and charging rates and this is where the problems start. For example, do not mix, gel with water, maintenance-free with maintenance type, dual 6 volt with 12 volt. This can cause a faster discharging water-filled battery to draw down a slower discharging gel-filled. I believe the advantage to 6V batteries is that they discharge slow and recharge quicker than most 12v, therefore having a 12v in the concurrent circuit would negatively impact the 6v batteries. Some above have mentioned that they have both type inline but they are isolated, so this satisfies the principal of keeping them separate. I experienced the "different attributes" battery issue first hand when I had TWO water-filled batteries and they were the same brand and model, but when one battery was failing (after 5 years of ownership) it caused the other one to seem it was failing too (I could never read higher than 13.2v even when charging). When I finally got smart enough to isolate each battery from each other, and found that the failing battery no longer recharged (remained around 11v) then the other battery perked up to over 14 volts when recharging and about 13v when operating and the single batter kept the trailer operating correctly. You can imagine how much worse it could have been even with good batteries, the one that has worse characteristics can cause the better battery(ies) to have degraded performance. I wouldn't connect dual 6v with 12v because I think this would be the biggest difference between 12v systems when it comes to different characteristics. But to answer your question having two switchable separate systems like what was mentioned above would work, but then one system is dead weight while the other is doing its job. But maybe when the one starts to discharge too much and you switch to the other provides redundancy. Let us know what you do. Many owners have some very creative setups.