I have a WFCO Converter (110 to 12) and a power panel (12V and 110v) with my travel trailer. One side is fed 110 v and the 12V panel is fed from the single 12V battery on the trailer tonque. I am installing a 2 battery (6V X2) battery bank under the sette with access to the outside that is getting charged from a solar panel and charge controller. I thought of rerouting the feed from the 12V tongue battery (supply to the power panel) through a DPDT switch. 6V battery bank or tongue battery to the power panel. I have already a isolation switch from the charge controller to the 6V bank. Any suggestions where to get a dpdt switch or could I use two battery selector switches (off/on 1 or on 2). Thanks

I use these BLUE SEA multi-position sealed high current battery switches. There are many marine qualified similar units out there but this is the one I have used over the years...Mine is a four position high current selector switch. (OFF-BAT1-BOTH-BAT2)The big reason i selected this switch is being sealed and also has MAKE BEFORE BREAK switch contacts inside to prevent internal switch arcing under load.I don't use these for any solar application but here is my general setup on using three of these switches with four GP24 batteries. Gives me two banks of two each batteries where i can switch to one or all four depending on what I want to do at the moment. These are a couple of drawing using two or four 6VDC batteries in series using these switches...Might give you some ideas on your application... I have never looked for 2P2T such high current switches before from BLUE SEA products...Roy ken

Use the battery switch on the positive. No reason for DPDT to switch the negative side.

In the first gentleman's reply he had a diagram showing the 6V battery banks were grounded. In my case the 12V tongue battery (both + and - ve) wires go to the connectors on the 12V power panel. I was going to cut the wires and add two wires from the 6V battery bank all terminating at the switch. Seemed to be the most easy thing to do. My trailer does not use a ground -ve except I believe for the brakeaway switch as the terminals exit from the battery box. The switch is right there on the tongue. Thanks again. Thought using two off/on battery switches from blue seas would work.

I would wager that you have a ground (-ve) to trailer frame from your 12V DC system. It is usual for the Mfg. to connect to frame ground for 12v devices rather than run a separate (-) back to a distribution point. The Blue Sea switches are top notch and using them to isolate banks is a great idea. You may wish to control converter charge to the banks, the output of the solar controller to banks, and inverter draw from banks. This makes controlling everything very flexible but there is some cost. I did just this thing, installing the switches at one distribution location. Schematic and pictures are here.

DPDT Switch for Battery Bank | Good Sam Community

23 Replies

wa8yxm
Explorer III
May 30, 2013
I would use the type of switch the first responder linked to.

By the way you do not need DPDT, SPDT is good enough That one actually has 4 throws.

It can connect A, B A+B or OFF. and it is a very good switch.
Dave_H_M
Explorer II
May 30, 2013
seems to me also that the spdt switch would work, however just saunter into Napa and get what you want. Or maybe ORilley's?
HiTech
Explorer
May 30, 2013
cdnmacgiver wrote:
So the -ve side of both battery banks (2X6V) and (12V) should be trailer grounded? ???? losses this way. Then switch only the +ve to the 12V power panel. Doesn't matter about the 110 to 12 converter from shore power when boondocking! Already have the off/1/2 switch. Should any protection be put in the grounded lines? Thanks again.

Yes grounded to the trailer frame as a floating ground system like a car. This does not mean you have to use the frame as the primary wiring for the - side. Just that the - of each battery should be bonded to ground on the trailer at some point.

Remember that when you are plugged in, the frame connects to earth ground via the 120 v system, and often the water in the plumbing also connects the frame to earth ground. So use the frame also as the ground reference in a sometimes floating 12v install.

Jim
BFL13
Explorer II
May 30, 2013
I just meant that at least you should be able to charge those 6s from the converter when solar can't.

Are the 6s under the settee in a closed battery box vented to the outside even if they are AGMs? Some have open air AGMs inside, but it is a risk they have decided to accept.
cdnmacgiver
Explorer
May 30, 2013
ON an afterthought I had already (last year) changed out the WFCO supplied converter (had already fried one tongue battery) with a progressive dynamics conversion kit from best converter. Seems to work well.
cdnmacgiver
Explorer
May 30, 2013
No I do not want to charge both banks from the solar panel. The bank switch is for supplying 12V to the 12V fused distribution panel. I either charge bank 1 (tongue battery) from shore and the converter or bank 2 (2 -6vs) from solar panel. The solar charge controller has an auxillary circuit to charge a second battery of lesser amperage. I decided to keep the two systems for charging completely separate at this time. I just wandered, with the two different battery banks having been -ve grounded at different battery banks, about any issues that I may not have taken into account.
BFL13
Explorer II
May 30, 2013
I got lost, but you want to be able to charge the tongue batt from the solar as well as the 6s. The converter should be able to charge the 6s too.

While camping off grid for max AH you should be able to parallel ("both" on the switch) the 6s and the 12 to get Peukert working for you. You can separate the 6s and the 12v for charging to full as desired where they will have different charging requirements going from say 90 to 100%. (You can charge them all at once going from 50-90% while camping though)
cdnmacgiver
Explorer
May 30, 2013
Now that I have the bank 1/off/bank 2 switch installed I have a question about compatability. I have the mains AC on from shore power with the converter on to supply 12V to the 12V panel and charge?? back to the 12V tongue battery (bank #1). The bank selection switch is on #1. At this time bank #2 is isolated and being charged by the solar panel and charge controller. both banks share a common -ve ground. Tongue battery 12V grounded on one side of trailer at brakaway switch. 2 (6V) batteries grounded on frame on opposite side of trailer. As long as I make sure the convertor and ac main switch is off when the 12V panel gets supplied from the Bank #2 everything should keep working. Just means bank #1 will sit by itself and not get charged. The electronic circuit for the dometec fridge (on propane) and the LP Gas monitor only draw 0.4 a. When the 12V fantastic fan kicks in then it jumps to 1.6 A. Have 220 Ahr capacity versus 60 to 80 on the tonguje battery. Thanks
mena661
Explorer
May 28, 2013
You only need to replace the inline circuit breaker if you expect to running larger loads than the fuse rating. BUT make sure that wire is rated to handle the higher loads first.
cdnmacgiver
Explorer
May 28, 2013
Thanks everyone. I just installed the 1/off/2 battery bank switch. I ran 4/0 wire for #1 to the 2-6V battery bank, and 4/0 for #2 to the original tongue battery (12V). Same for the common to the original tongue batter connection at a inline circuit breaker underneath the trailer. Seems a little small for the connectors. Original wire looks like only #8 to the distribution panel. Took reading off the battery remote metering. Loads are a lot less then the fusing in the 12V distribution panel. So I am now set up to run 110V shore power with converter to supply 12v and charge tongue battery or 12V from tongue or 6V bank (converter and mains off). Should I replace the inline circuit breaker with a larger one. Can't make out the size. All in all the amsolar supplied equipment works well. Just wish there was a less complicated information guide for the remote. Thanks again.