I went to my local cosco to get a couple new 6 v batteries. I inquired, where are the 6 v RV batteries. We have two this one is bigger. Bigger is always better with batteries. The salesman loaded two in my cart. I get home install my new batteries. First my thing I noticed the generator didn't start. Nothing. I tried my slide out it took off twice as fast. Right then I realized I had a problem. In my hast to install the new batteries I didn't realize I had two 12 volt batteries. So I put 24 v to my coach. Is there any chance I really screwed up? I am hopping they will take the batteries back, if not I will have a couple batteries for my tractors. Should I use the batteries in parallel, or just get two 6v batteries and use them in series? Stan

It could be very ugly. Start checking fuses but it wouldn't be surprising to have toasted circuit boards etc.

It's hard to say what you may have messed up by wiring two 12V batteries in series. You may have smoked the electronic ignition module on your generator. Your slide motor is likely ok. Hopefully the board in your fridge isn't fried (should be ok if it was off). Yes, the 6V batteries should be in series, but obviously 12V should be in parallel.

Check everything. Be hopeful.“Should I use the batteries in parallel, or just get two 6v batteries and use them in series?” Nothing wrong with two 12s but many believe two 6s are better. Use them IMO.

Being that we had two sets of 12V batteries prior to the pair of 6V batteries we have now, the two 6V batteries perform much MUCH better. Unlike 12V batteries wired in parallel, the 6Vs drain in unison and charge in unison which provide more extended 12V power than two 12Vs.Our 12V batteries wired properly for power balance, one 12V battery always drained faster than the other. When charging them, one would always get over-charged while the other never gets fully charged. Eventually one battery becomes ill from it all, causing us to replace the batteries prematurely.Our 12V batteries, year #1 was always good. Year #2 was okay. Year #3 was rocky. Once we tried year #4. As Trump would say, year #4 was a disaster. With our 6V batteries, they are AGM batteries selected for their maintenance-free benefit, we finished year #3 and they performed like year #1. They do so well that I leave them wired up to the rig off season so I have interior lighting. When I power-up, my power panel display shows their voltage around 12.6V which is right where they should be. I do put them on a secondary Black & Decker charger about once every 2 to 3 months to make sure all remains well.I would definitely exchange the 12V batteries for 6V at Costco. You can get standard lead acid or AGMs there. We bought our 6V AGM Duracell brand at Costco. Tell Costco the truth, you thought the sales guy placed two 6V batteries in your shopping cart. When grabbing a pair off the rack, try your best to pick ones with the same production date code so they are better balanced.If switching from 12V to 6V batteries, make sure your battery compartment can handle their increased height. 6V batteries are a few inches taller. AGM batteries will require chargers with an AGM setting. So if switching to AGM technology, make sure your RV charger has an AGM setting. I think the AGM setting pumps out a slightly higher voltage.As far as damage is concerned, some RV appliances may have over-voltage protection built into them. Maybe your generator protected itself by not responding. Items never turned on will surely be fine. The things that don't work at all are easy to identify. It's the things that could die a slow death that are concerning like your slide-out motor. But on the bright side, you learned of the error immediately so I think if it works well, you'll be fine for the long haul.

Motors are probably fine but anything with electronics may be fried like the furnace and water heater control boards, detectors, stereo, etc.All you can do is try them.Good luck!

Did I scrwew up anything | Good Sam Community

azrving
Explorer
Dec 19, 2017
It could be very ugly. Start checking fuses but it wouldn't be surprising to have toasted circuit boards etc.
rjstractor
Nomad
Dec 19, 2017
It's hard to say what you may have messed up by wiring two 12V batteries in series. You may have smoked the electronic ignition module on your generator. Your slide motor is likely ok. Hopefully the board in your fridge isn't fried (should be ok if it was off). Yes, the 6V batteries should be in series, but obviously 12V should be in parallel.
Lwiddis
Explorer II
Dec 19, 2017
Check everything. Be hopeful.

“Should I use the batteries in parallel, or just get two 6v batteries and use them in series?” Nothing wrong with two 12s but many believe two 6s are better. Use them IMO.
ron_dittmer
Explorer II
Dec 19, 2017
Being that we had two sets of 12V batteries prior to the pair of 6V batteries we have now, the two 6V batteries perform much MUCH better. Unlike 12V batteries wired in parallel, the 6Vs drain in unison and charge in unison which provide more extended 12V power than two 12Vs.

Our 12V batteries wired properly for power balance, one 12V battery always drained faster than the other. When charging them, one would always get over-charged while the other never gets fully charged. Eventually one battery becomes ill from it all, causing us to replace the batteries prematurely.

Our 12V batteries, year #1 was always good. Year #2 was okay. Year #3 was rocky. Once we tried year #4. As Trump would say, year #4 was a disaster. With our 6V batteries, they are AGM batteries selected for their maintenance-free benefit, we finished year #3 and they performed like year #1. They do so well that I leave them wired up to the rig off season so I have interior lighting. When I power-up, my power panel display shows their voltage around 12.6V which is right where they should be. I do put them on a secondary Black & Decker charger about once every 2 to 3 months to make sure all remains well.

I would definitely exchange the 12V batteries for 6V at Costco. You can get standard lead acid or AGMs there. We bought our 6V AGM Duracell brand at Costco. Tell Costco the truth, you thought the sales guy placed two 6V batteries in your shopping cart. When grabbing a pair off the rack, try your best to pick ones with the same production date code so they are better balanced.

If switching from 12V to 6V batteries, make sure your battery compartment can handle their increased height. 6V batteries are a few inches taller. AGM batteries will require chargers with an AGM setting. So if switching to AGM technology, make sure your RV charger has an AGM setting. I think the AGM setting pumps out a slightly higher voltage.

As far as damage is concerned, some RV appliances may have over-voltage protection built into them. Maybe your generator protected itself by not responding. Items never turned on will surely be fine. The things that don't work at all are easy to identify. It's the things that could die a slow death that are concerning like your slide-out motor. But on the bright side, you learned of the error immediately so I think if it works well, you'll be fine for the long haul.
ScottG
Nomad
Dec 19, 2017
Motors are probably fine but anything with electronics may be fried like the furnace and water heater control boards, detectors, stereo, etc.
All you can do is try them.

Good luck!
ksg5000
Explorer
Dec 19, 2017
Wire up your new batteries correctly and see what works/doesn't - and report back.
Dusty_R
Explorer
Dec 19, 2017
I prefer 2 12 volt batteries. Two sixes may put out a little more, but if you are out in the boonies and one battery quits and it is a 6 volt you are up the creek. But if it's 2-12s you can disconnect it and get by on one.
Our last mh we replaced the 12's once in 13 years, and they were still good when we traded it.

Dusty
azrving
Explorer
Dec 19, 2017
Dusty R wrote:
I prefer 2 12 volt batteries. Two sixes may put out a little more, but if you are out in the boonies and one battery quits and it is a 6 volt you are up the creek. But if it's 2-12s you can disconnect it and get by on one.
Our last mh we replaced the 12's once in 13 years, and they were still good when we traded it.

Dusty

I'm not following you. So you are saying that true deep cycle sixes are prone to fail sooner than a dual purpose? Running two 12's is preferred in case of failure yet they lasted 13 plus years? Doesn't seem like building around potential failure is worthwhile. Getting the advantage of true deep cycles seems worthwhile. Am I looking at it wrong? I can get 630 ah of sixes into a space that that I can only get 400 ah of 12's.
stansgreyhawk
Explorer
Dec 19, 2017
As hard as I try to ruin things I don't think I did any damage by hooking up 24 volts to my system. I only ran my slide then I realized I had a problem. Had I tried to run lights, pump, ref control I may have done some damage. Even putting 24 v to my Ford would have been a real mess.after worrying about it most of the evening. I installed a 12 volt battery every things seams to be ok. I found diesel engine will run on a 50 50 mix of gasoline, and diesel. Another time I tried to ruin my John Deere tractor motor. Got lucky there also. Thanks for the information. I will install two 6 V batteries, like I had in the first place. Stan
Photomike
Explorer III
Dec 19, 2017
azrving wrote:
Dusty R wrote:
I prefer 2 12 volt batteries. Two sixes may put out a little more, but if you are out in the boonies and one battery quits and it is a 6 volt you are up the creek. But if it's 2-12s you can disconnect it and get by on one.
Our last mh we replaced the 12's once in 13 years, and they were still good when we traded it.

Dusty

I'm not following you. So you are saying that true deep cycle sixes are prone to fail sooner than a dual purpose? Running two 12's is preferred in case of failure yet they lasted 13 plus years? Doesn't seem like building around potential failure is worthwhile. Getting the advantage of true deep cycles seems worthwhile. Am I looking at it wrong? I can get 630 ah of sixes into a space that that I can only get 400 ah of 12's.

What he is saying is that if you have a 12V battery you can run your RV. If you have two 12V and one fails you can run your RV off the remaining one. If you have two 6V and one fails you are up the creek without enough power :-) A lot of people that run 6V run 4 so you can always disconnect two batteries and still run the RV.