Battery Question on WBG View

[WNDOPDLR]

My wife and I bought our first RV, an 07 View a couple weeks ago. There are three batteries on board, one under the hood for the engine and two coach batteries. Currently we have two deep cycle 6V batteries wired in series to supply 12V to the coach. Seems to me that two 12V batteries wired in parallel would give me twice the reserve power. The only down side I see is whether the charging system will handle it. Any thoughts from the community?

[RV Vagabond]

Yes, 2 6-volts are like 1 12-volt, and will drain pretty quickly. I would replace them with 2 12-volt and if there is room then add more batteries depending on how much power you use and whether you will have plug in power or solar chargers.

[F76Marion]

Wndop,

Don't be offended, but you (and many other people) have this figured out backwards.

If you have 2ea GC2s (golf cart batteries - real deep cycle) in series, the bank will be rated at about 220 Ampere-Hours.

If you have 2ea Group 31s (real deep cycle are hard to find) in parallel you MAY have a bank rated at near 220 Ampere-Hours.

But, there are problems with lead/acid batteries in parallel. They just don't play nicely together. One will want to slack off while the other works. Yes, they can trade off at this, but you will be hard pressed to get capacity of parallel L/A batteries as X2. You may get 1.75 if you are very careful, but more often than not what I have seen is closer to 1.5. And, because they are not true deep cycle, you can't use more than 50% of the capacity or the jars are damaged.

If you put the batteries in series, there is no effect on the capacity because the same current flows through both at the same time and that has to happen. Then there is another gain for the GC2s. Because they are true deep cycle construction, you can use 60% of the capacity and not cause harm.

So, with the golf cart batteries, you not only have more usable capacity, but they are not being stressed as hard and will probably live longer.

Frank

[TQ60]

You will or rather should get what you buy.

What that means is if you buy 2 group xx batteries rated at 100 amp hours each and place them in parallel and charge them properly you will get 200 amp hours from them.

Simple.

But...

Most folks do not read the data sheet to understand how their batteries are rated or fully use their capacity.

True deep cycle batteries are designed to discharge to 1.75 VPC and a few to 1.6 VPC but doing so does induce wear on the battery.

This is considered a "cycle" and there are different opinions on how much discharge constitutes a true cycle.

Most batteries are generic rating of 1000 or so cycles.

So if you fully charge and fully discharge your battery every day then the design life would be about 3 years.

Also note that the industry fail point is 80% capacity.

So for weekend or summer use just use them and be sure to use the proper care and feeding and you will be fine.

Before buying a new one have the vendor provide the data sheet that shows rate of charge and discharge and have them explain how the battery is rated and how it will preform in your application.

There are standby batteries intended to provide stand by service such as telephone systems and cycle batteries used in UPS or golf carts.

These are designed for consistent charge discharge cycles as they are intended to be used as a primary power source.

[twinboat]

Originally Posted by RV Vagabond

Yes, 2 6-volts are like 1 12-volt, and will drain pretty quickly. I would replace them with 2 12-volt and if there is room then add more batteries depending on how much power you use and whether you will have plug in power or solar chargers.

If 2, 6 volt are like 1, 12 volt, WHY do they put 6, 6 volt batteries in electric golf cars, instead of 3 12 volts.

Because most 6 volt batteries are built for Golf Cars. ( GC2 ). They are high capacity, deep cycle batteries. They are designed to be discharged and recharged many ( 1000 ) times.

They go out, day after day, getting heavy use and then charged at night.

When a business uses hundreds of 6 volt batteries, it is due to cost and performance.

Anything other then deep cycle batteries are designed for short bursts of power to start engines.

Most 12 volt batteries are hybrid start batteries. Deep cycle batteries are only now, getting more popular.

Stick with the 6 volt pair.

[jackfish]

Originally Posted by twinboat

Stick with the 6 volt pair.

Yes this.