Two 6v AND two 12v

[FireMech]

Has anyone done this? I currently have two 6 volt wired in series but came across two brand new interstate deep cycle 12 volt batteries for practically nothing. I know the system should be balanced but the price is right....

[PerryB]

Yes, you could do that with no problem as long as you wire it properly. The perfect set-up would be two BIG 6v AGM's but that is BIG $$$. I've never done exactly what you're talking about, but I've had three trailers with parallel battery systems and never a problem (when you put your two existing 6v's in series you basically just created one 12v battery, which will now be put parallel to the new 12's). Its not theoretically ideal, but at the low load rate they'll be working at you'll have no issues-unless you plan on running a large inverter and really working the batteries. Then you need to be balanced. You'll certainly have lots of amps for the camp.

[FireMech]

Sounds good, I wasn't sure if others have tried this. I don't plan on running a large inverter, just want to have more capacity.

[Bob Landry]

Functionally, it will work, but unless batteries connected together are of similar types, capacities and condition, you will probably run into charging issues and end up with both batteries charged less than full. Also the lesser charged battery will draw from the higher charged one thus shortening the time between charges. In marine applications we never mix and match in the 12V systems. YMMV

[SAABDOCTOR]

LOOK UNDER THE HOOD OF YOUR DIESEL TRUCK. two 12volts wired parralell. as long as they are the same amp ratting and in good condition they will work sorry did not mean to yellforgot the caps lock.

[ktmracer]

Originally Posted by FireMech

Has anyone done this? I currently have two 6 volt wired in series but came across two brand new interstate deep cycle 12 volt batteries for practically nothing. I know the system should be balanced but the price is right....

with a combo like this the best thing to do is:

1) wire the 12V in parallel as one bank and leave the 6V wire together in series as one bank
2) Get a perko or similar battery disconnect switch with an battery 1, battery 2 and off switch
3) Connect the 6V to either battery 1 or battery 2
4) connect the 12V bank to the other battery position
run off one of the battery positions till they are discharged enough that you want to switch, the switch over. do the same thing to charge.

Really won't cost much extra and won't take much extra wiring and will yield much much better results and battery life.

While you could wire it together as one big bank, combining individual banks with noticeably different types and capacities especially 12V and 6V really doesn't work well. they will try to discharge or charge at different rates, but can't because of the other batteries in the bank.

[FireMech]

Thanks for the replies, I like the idea of two different switched banks. I'll give it a try but will eventually buy two more 6 volts for a total of four.

[ktmracer]

Originally Posted by FireMech

Thanks for the replies, I like the idea of two different switched banks. I'll give it a try but will eventually buy two more 6 volts for a total of four.

Once you go to all 6V of the same AH, then wire them into 1 big parallel bank. Reason is that you will get more AH than as seperate banks since AH is dependent on current draw. The lower the draw the higher the total AH available. for example, the common T-125 varies from about 185A at a 75A draw up to 266AH at a 2.6A draw. Two banks cuts the current per bank in half moving you up the AH curve.

But again, don't try this with different AH or different type batteries.