6 volt batteries

[Erniek]

Does anyone know if there is any advantage to adding a third 6 volt battery (in parallel to one of the existing 6 volt batteries)? I am trying to increase my amp/hr capacity. I have two 6 volt batteries wired in series now. The guy at the battery place told me that adding a third would increase the amp/hr capacity, but i am not convinced.

Thanks,

Erik

 

[Kirwin]

In theory yes, in practice no. You would need to add 2 more in a series parallel arrangement to double your Amp-hr capacity. Two more batteries connected just like your other two, however all the batteries need to be equal capacity for best results. Adding two new batteries to a system with two old batteries will just age the new batteries faster as they will be doing most of the work. There are schematics at RV Dreams.com if your interested. Ken Irwin

 

[Road Dog]

You would need to add 2 6V batteries and like Kirwin said, you shouldn't mix old and new batteries. To do it, wire 2 6V batteries in series to create a 12V module which would go in parallel with the existing 12V module.

 

[Erniek]

That is what I thought. Thanks for the replies.

Erik

 

[KATOOM]

I'm at a loss as to why the guy at the battery place told you that adding a third would increase the amp/hr capacity. Does this battery sales person not understand how batteries work? Yes, as already mentioned, you need two more 6 volt batteries to do what you want but really four 6 volt batteries is going to be a lot and really heavy. Have you considered setting up a little solar system which would help offset your usage while unplugged? One time I thought about configuring a large battery bank but after talking with many RV forum people, I've come to realize that this may not be what I'm after. The hard part about solar is you have to learn all the ins and outs of what to do and what to get to have something useful.

 

[Loren]

Erik,

Let’s say you currently have two 6-volt, 100 Amp-Hour batteries wired in series to get 12 volts.

If you install a third in parallel with one of them you essentially will still have two batteries in series, but one will be 100 Amp-Hours and the other will be 200 Amp-Hours. As you use power from these TWO batteries (one 100 Amp-Hour and one 200 Amp-Hour) each battery will be providing half of the power because they are in series. When the 100 Amp-Hour battery is depleted, the other (200 Amp-Hour) battery will be only half-depleted. However, with one of the two batteries dead (the 100 Amp-Hour battery), you will be getting just 6 volts from the installation – no useable power.

This is exactly the same as when one battery goes dead in a flashlight that takes two batteries. You don’t get much light out of that flashlight, even though the other battery may be brand new. Flashlight batteries are in series, just like the 6-volt batteries in your RV.

If, instead of installing just one more battery, for a total of three, you install two more batteries, for a total of four, you will indeed double the capacity of your installation. You would have a pair of 6-volt batteries in parallel wired in series to another pair of 6-volt batteries that are also in parallel. This would create the equivalent of two 200 Amp-Hour batteries in series.

The bottom line is that three batteries would be worse than the two you have now, but four batteries will double your capacity.

Good luck,
– Loren

 

[Shadrach]

I have 2 6 volts on my TT and also have an 80 watt and a 125 watt Solar panel on the roof. For weekend or short trips when there is lots of sun these work pretty good. The solar panels keep the batteries topped up while travelling and between trips. Of course I can't use my A/C but I also have a 1750 watt inverter which converts that power to 120 and will do most thing I need although the microwave is hard on power. During the off season, that is when snow covers up my solars, I remove the batteries and place them on the bench in my unheated garage. The first of each month I give them 24 hours of charge with an old fashioned battery charger. I charge them up when they are hooked together and then AFTER they are charged up I top up the water if necessary. If you top them up before you charge them up you could have them over flow as the fluid expands.

By doing this they are alway kept charged and never freeze, not even when it get real cold, like -35 below for example. I get 7 years out of a pair. Unfortunately I don't have room for 4 6 volts. It would also add another 150 lbs to the tongue weight. David

 

[bigceltic]

I swapped out my 2 12V batteries and replaced them with 4 GC batteries which has really helped when dry camping. Was able to fit this box (http://www.allbatterysalesandservice.com/browse.cfm/4,5576.html) where the old 12v battery boxes were.

George

 

[SnoKing]

Also putting a new battery in parallel with an older battery very soon makes the new battery "older" like the existing one! So not good!

 

[Bohemian]

Batteries should always be matched. Same brand, same model, same manufacture date, age, and use. If not the new will degrade to the state of the old.

There are two advantages of 6V batteries. Series hookup vs parallel, a minor advantage with good quality modern batteries. Therefor not important. Size. larger cell size leads to more energy per volume and per weight. 6V batteries have larger cells and come in larger sizes, so they have larger capacities per weight and size. If you compare a larger 12V battery to a pair of the smaller 6V batteries with the same net specs, there is no advantage to the 6V batteries and they add complexity and more components.