Deep Cycle Batteries

[High Desert Ranger]

Why would someone prefer to use 2x 6v Deep cycle batteries connected in series to make 12v as opposed to using 2x 12v deep cycle batteries connected in parallel?

 

[Ozwynn]

you got me. why would somebody do that?

 

[High Desert Ranger]

you got me. why would somebody do that?

Don't know, had someone come into my work today and ask for the 6v batteries for his RV.

 

[Ozwynn]

some of the older RVs used two 6 volt batteries for the coach. most older Diesel equipment used multiple sets of 6 volt batteries wired like that. infact ..... a long long time ago everything automotive used 6 volt batteries. I thought you were talking about a winch set up or something.

 

[High Desert Ranger]

some of the older RVs used two 6 volt batteries for the coach. most older Diesel equipment used multiple sets of 6 volt batteries wired like that. infact ..... a long long time ago everything automotive used 6 volt batteries. I thought you were talking about a winch set up or something.

Eventually I will be adding a winch to my vehicle, but before I do that I'll already have installed 2 of some sort of deep cycle battery. I had bee seriously considering using 2 group 27 Deep cycle Marine batteries but have yet to come to a final decision.

 

[arrabil]

Isn't it because the load accross each battery is less so they last longer?

My brother-in-law always wires his boat's electric motor to two batteries because he says he gets more run time that way than running one down and hooking up the second.

 

[High Desert Ranger]

Isn't it because the load accross each battery is less so they last longer?

My brother-in-law always wires his boat's electric motor to two batteries because he says he gets more run time that way than running one down and hooking up the second.

2 6v bolt batteries, or 2 12v batteries?

 

[arrabil]

Why would that make a difference?

EDIT: I see, series or parrallel. Either way the batteries share the load, no?

 

[krugford]

When batteries are hooked in series, you'll have a harder time keeping them balanced. Even due to manufacturing tolerances, if one battery has a slightly lower capacity than the other, then that battery will drain faster because it's having to source the same current as the "stronger" battery even though it's voltage may be lower. It's also be an exponential decay on the weaker battery. Torwards the end, it'll just turn into a parasitic load on the system when it gets really low. When they are hooked in parallel, they will keep themselves balanced naturally.

As for your deep cycle selection, why not go with a group 29 marine? If I recall, they are the same size and offer a higher capacity. But they also cost more. I guess it could be a future upgrade. You wouldn't have to re-do a mounting system because they are the same size...

 

[High Desert Ranger]

I might have found an answer to my question, and it's reasonable and completely nixes the idea of using 6v batteries.

Let's take 2 nearly identical batteries except for these facts that 1 battery is 6v and the other is 12 volt. And rea lets say that the 6v battery has a 240 min reserve capacity and 625 CCA and the 12v has a 180 min reserve capacity and 625 CCA. So right now the 6v has a better looking reserve capacity.

You connect 2x 6v batteries in series to make 12v and what do you have?
12v 625 CCA and still 240 min reserve capacity.

You connect 2x 12v batteries in parallel which still makes 12v and what do you have?
12v 1250 CCA and 360 min reserve capacity. (Because the load is split between the batteries and not using the full capacity of them)

So in this situation the 12v batteries look like the better deal.

The only question that I would have is the long term durability of the 6v vs. the 12v batteries.