Golf Cart Batteries

[AJMike]

I finally saw an RV that came from the manufacturer with two 6 volt Golf Cart batteries wired in series rather than two 12 volt wet cell batteries wired in parallel. I did not know that any manufacturer used that design when building the RV. Of course I have some questions.

1) Is it not inherently risky to only have one series connection for a coach battery? I assume that any issue with one of the batteries connected in series will cause a loss of all power to the coach since there is only one battery in the sense that two batteries in series provide essentially one power path.

2) How do golf cart batteries differ from wet cell batteries? Not in construction - I don't much care about the internals - but rather in how they react to charge and discharge. Do they charge more quickly/less quickly/the same as other wet cells? Can they sustain higher discharge rates? Or do they discharge more slowly?

3) What is the appeal of 2 golf cart batteries connected in series rather than 2 wet cells connected in parallel? Is it just a higher AH rating? The batteries (Interstate GC-2) were rated at 210 or 225 AH, but I assume that is for both batteries)? Or is there some other reason to use that configuration?

I know I tend to post a lot of questions, but it has been a life-long issue with me. When I was an undergraduate I asked more than half the questions in my classes and kind of annoyed the faculty, but I am just very curious about things like this.

[powercat_ras]

Appeal is more power stored in the same battery compartment floor space. That said they are taller and you have to confirm that the battery compartment can safely handle the taller batteries.

Not inherently risky, there are literally millions of RVs using pairs of 6 volt golf cart batteries in series.

Golf cart batteries are wet cell batteries , 6 volt batteries have 3 cells which means there is less of the case space used for plastic spacers and such so they can be engineered with more storage in the same space.

The best indicator of how good a wet cell deep cycle battery is, golf cart or not, is weight. The more lead the more it can store and the longer it will last.

A really good balance between cost and storage for golf cart batteries are the 200 amp-hour Interstate 6 volt golf cart batteries sold by Costco. That's what I am using. 4 years old and still going strong!

[AJMike]

Originally Posted by powercat_ras

Appeal is more power stored in the same battery compartment floor space. That said they are taller and you have to confirm that the battery compartment can safely handle the taller batteries.

Not inherently risky, there are literally millions of RVs using pairs of 6 volt golf cart batteries in series.

Golf cart batteries are wet cell batteries , 6 volt batteries have 3 cells which means there is less of the case space used for plastic spacers and such so they can be engineered with more storage in the same space.

The best indicator of how good a wet cell deep cycle battery is, golf cart or not, is weight. The more lead the more it can store and the longer it will last.

A really good balance between cost and storage for golf cart batteries are the 200 amp-hour Interstate 6 volt golf cart batteries sold by Costco. That's what I am using. 4 years old and still going strong!

Do they take a charge similarly to 12 volt wet cells? Are they OK in really cold weather? And really hot weather? Are they sealed? Or do they need regular maintenance (which means adding water when there did not seem to be any room to open the tops).

[Winterbagoal]

Price is the reason many use them. They're probably a little more durable than 12V peers, due to the thicker plates, as previously mentioned. Their weight and physical dimensions are sometimes a limiting factor. Wet cells do require regular maintenence, which is also a limiting facotr for some. I think they come in a maintenence free version, but then they get pricier. Your comment about no redundancy if one fails in a pair is also valid. If you only have one pair.

[powercat_ras]

Do they take a charge similarly to 12 volt wet cells? YES

Are they OK in really cold weather? YES

And really hot weather? YES

Are they sealed? NO Only AGM and LiFe04 are maintenance free (not accurate to say they are sealed as they have saftey vents that keep them from bulging and rupturing if they are improperly used)

Or do they need regular maintenance (which means adding water when there did not seem to be any room to open the tops). YES. All wet deep cycle batteries have removable caps over the cells and need to checked and distilled water added to keep liquid level at the bottom of the cap holes.

[AJMike]

Originally Posted by powercat_ras

Are they sealed? NO Only AGM and LiFe04 are maintenance free (not accurate to say they are sealed as they have saftey vents that keep them from bulging and rupturing if they are improperly used)

Or do they need regular maintenance (which means adding water when there did not seem to be any room to open the tops). YES. All wet deep cycle batteries have removable caps over the cells and need to checked and distilled water added to keep liquid level at the bottom of the cap holes.

Thanks. I did not know. I thought I had seen regular wet cell batteries that were sealed and maintenance free, but perhaps those were really AGM batteries.

The battery compartment in our Fuse leaves next to no room to remove the caps and add water, and is not on a slide-out so you have to physically disconnect and remove the batteries to add water. Don't have that problem now with the Lithium batteries, but I guess it would be a problem with golf cart batteries.

I have to say that I don't know why the RV manufacturers design the battery compartments in such a way as to make maintenance such a problem. It should not take much effort (or much extra money) to put the batteries on some kind of slide-out to ease adding water, but then what do I know?

I do have one additional question. If 2 of these are wired in series what is the AH rating of the connection? The same AH rating as each one? Or double? The reason I ask is that I saw a sealed AGM golf cart battery on Amazon listed as 225 AH, so does that mean that 2 wired in series are also 225AH? Or 450 AH?

[Retiree1]

Golf cart batteries are designed to be more durable, to store more amp-hours, and to handle more discharge cycles than standard wet cell batteries. I use two Trojan T-125 golf cart 6 volt batteries in place of the original NAPA supplied 12 volt batteries in my Navion. They are slightly larger and heavier, but increased the amp-hour capacity for my rig from 140 Ah to 240 Ah (usable storage from 70 Ah to 120 Ah at 50% of battery discharge). That's about a 70% increase in usable amp-hours. This gives me the most bang for the buck when using a flooded lead acid type battery. The attached graph shows the discharge losses in a Trojan T-105 golf cart at various storage temperatures. I would assume that most brands of batteries would be similar. You can see that the battery loses much more energy when stored at high temperatures versus low temperatures. In theory, you should be able to store a fully charged battery over the winter and only lose about 20% of the charge if the battery is disconnected from the vehicle. Two 12 volt 70 Ah batteries connected in parallel will provide 140 Ah of total storage capacity, while two 6 volt 240 Ah batteries connected in series will provide 240 Ah of total storage capacity.

[powercat_ras]

RV system Amp-Hours capacity is at the rated battery system voltage.
RV System DC voltage is 12 volts since that is what all the DC loads in our RVs use. That said, there are a few exceptions where certain RVs like the Winnebago Travato 59KL and 59GL that have a 48 volt LiFe04 battery pack and 48 volt to 12 volt converters to provide power to standard 12 volt loads.

To make a 12 volt battery system takes two same size and type 6 volt batteries in series.

So, to get 200 amp-hours at 12 volts takes two six volt 200 amp-hour golf cart batteries connected in series.

[AJMike]

Originally Posted by powercat_ras

So, to get 200 amp-hours at 12 volts takes two six volt 200 amp-hour golf cart batteries connected in series.

Thank you. That is what I assumed, but it is good to have confirmation.

[Old Navy]

Originally Posted by AJMike

I thought I had seen regular wet cell batteries that were sealed and maintenance free, but perhaps those were really AGM batteries.

There are generally 3 types of Sealed Lead Acid batteries.

"Maintenance Free" Flooded Lead Acid
Absorbent Glass Mat
Gel

All three are sometimes marketed as "maintenance free" and "sealed".
All three are "Sealed Lead Acid", or more accurately "valve-regulated lead-acid" as they have a valve to prevent pressure buildup and case bulging.

Marketing "Sealed Lead Acid Batteries" can be misleading, and you have to verify the technology you are actually getting. Many have purchased "maintenance free" flooded batteries assuming they are AGM.

[DavidM]

I have used GC batteries for 20+ years on cruising sailboats and trawlers. They are the goto battery for small or large battery banks on boats. LFP's are catching on but some of the advantages like light weight are not all that important on a boat.

So here are some answers based on that experience.

Originally Posted by AJMike

I finally saw an RV that came from the manufacturer with two 6 volt Golf Cart batteries wired in series rather than two 12 volt wet cell batteries wired in parallel. I did not know that any manufacturer used that design when building the RV. Of course I have some questions.

1) Is it not inherently risky to only have one series connection for a coach battery? I assume that any issue with one of the batteries connected in series will cause a loss of all power to the coach since there is only one battery in the sense that two batteries in series provide essentially one power path.

Well three cells connected to three separate cells with a wire is no more risky than 6 cells connected together in one battery with an internal buss.

2) How do golf cart batteries differ from wet cell batteries? Not in construction - I don't much care about the internals - but rather in how they react to charge and discharge. Do they charge more quickly/less quickly/the same as other wet cells? Can they sustain higher discharge rates? Or do they discharge more slowly?

Construction is important. GCs have thicker plates that prevent swiss cheesing as lead drops off of the plates and settles in the bottom as lead sulfate. Filler caps are important to check SG, water and add water. GCs have more room at the bottom for sulfate buildup because it can build up and short the plates on other FLA batteries. GCs also have more headroom for electrolyte which can prevent uncovering the plates with loss of electrolyte. One downside is GC batteries are taller.

Back to your question though: No real difference in charge and discharge rates except that starting batteries can supply hundreds of amps for a few seconds to start the engine whereas GC batteries (at least one pair) cannot


3) What is the appeal of 2 golf cart batteries connected in series rather than 2 wet cells connected in parallel? Is it just a higher AH rating? The batteries (Interstate GC-2) were rated at 210 or 225 AH, but I assume that is for both batteries) The 210 Ah rating is for each, but it takes two to make 12V and provide 210 Ahs at 12V. Or is there some other reason to use that configuration?

There is no benefit to two 6V series connected batteries vs two 12V batteries connected in parallel.

I know I tend to post a lot of questions, but it has been a life-long issue with me. When I was an undergraduate I asked more than half the questions in my classes and kind of annoyed the faculty, but I am just very curious about things like this.

Golf cart batteries supply the most amp hours for the buck for any type of battery including LFPs. They are made by the millions to support the millions of golf carts. Any manufacturer supplying an inferior product will quickly be run out of that business. GCs have evolved over time to serve the slow discharge deep cycle profile that a golf cart needs which is exactly what we need in an RV house battery.

David

[AJMike]

Originally Posted by Old Navy

There are generally 3 types of Sealed Lead Acid batteries.

"Maintenance Free" Flooded Lead Acid
Absorbent Glass Mat
Gel

Ah. So my original opinion, that there are maintenance free regular wet cell batteries, was correct.

I looked on Amazon and all of the maintenance free batteries were AGM or Gel so I thought that my first opinion was wrong.

[AJMike]

Originally Posted by DavidM

Well three cells connected to three separate cells with a wire is no more risky than 6 cells connected together in one battery with an internal buss.[/B]

Yes, but I was asking about 3 cells in 2 batteries connected in series as compared to 6 cells in 2 batteries connected in parallel. It just seems inherently more likely to fail since a failure in any cell in a series connection will cause complete failure while a failure in any cell in a parallel connection will still leave the system working. One battery short, but still working.

[DavidM]

Originally Posted by AJMike

Yes, but I was asking about 3 cells in 2 batteries connected in series as compared to 6 cells in 2 batteries connected in parallel. It just seems inherently more likely to fail since a failure in any cell in a series connection will cause complete failure while a failure in any cell in a parallel connection will still leave the system working. One battery short, but still working.

OK I see what you are saying now. But if one of the two 12V batteries fails, particularly with shorted plates, it will quickly bring down the other. So the result is similar.

I don't know why the golf cart industry settled on 6V batteries as their base. But what would you prefer: two industry standard, known true deep cycle batteries wired in series or two starting batteries wired in parallel with thin plates, not much room below or above the plates for electrolyte, etc?

Like I said the boating industry settled that question a long time ago.

David

[Old Navy]

Originally Posted by AJMike

Ah. So my original opinion, that there are maintenance free regular wet cell batteries, was correct.

I looked on Amazon and all of the maintenance free batteries were AGM or Gel so I thought that my first opinion was wrong.

Yes, you were correct. Here's the crappy Maintenance Free FLA battery the dealer provided with my trailer:

https://www.centennialbatteries.com/...intenance-free

As for reliability, the better 6V CG batteries are built like tanks. All of the internal components are bigger and beefier. If anything, I would expect fewer failures with 6V batts. But there are exceptions, and some battery manufacturers make very large, heavy 12V batteries that are constructed like tanks also.

[DavidM]

Originally Posted by Old Navy

But there are exceptions, and some battery manufacturers make very large, heavy 12V batteries that are constructed like tanks also.

Who?? Maybe Lifeline at 2-3 times the price of a run of the mill GC battery.

David

[Old Navy]

Originally Posted by DavidM

Who?? Maybe Lifeline at 2-3 times the price of a run of the mill GC battery.

David

Yes, they are definitely rare exceptions. Lifeline, Trojan, Rolls Royce. There might be others,not sure. And they are big and heavy beasts. To make a 12V battery that is equivalent to 2 GC2 6Vs, it has to be as big and heavy as 2 GC2's.

[BobC]

One of these will take care of filling in tight spaces:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

You'll also need this:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[AJMike]

Originally Posted by BobC

One of these will take care of filling in tight spaces:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

You'll also need this:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

And, I would think, some hand-held dentist type mirror so you can see the water level and know when it is full. I don't think you want to fill it until it overflows.

[BobC]

Originally Posted by AJMike

And, I would think, some hand-held dentist type mirror so you can see the water level and know when it is full. I don't think you want to fill it until it overflows.

No need, everything is sealed, the bulb pump just gets hard once it's full. If you've ever pumped the hand bulb on the gas line to an outboard motor, it's the same principle.