6V Batteries for boondocking 2018 Micro Minnie 2108DS

KGs2108DS · 10-29-2022, 11:47 AM

I'm considering purchasing 2 6VDC "golf-cart" batteries rather than a new 12VDC 115Ah deep cycle battery. I've encounter 2 Winnebago owners that tell me basically the following (together with a bit of research I've done)...
For example I'm looking at a Traveller 6V 875A (700 cold cranking A). my understanding is that two of these batteries hooked in series would provide 230Ah, thus twice the run time for my trailer (and twice the charge Time too). However I cannot find a clear answer to whether this conversion is accurate. Apparently it depends on the BCI Battery Group (can't find this for "golf cart" batteries. Can someone shed light on this? thanks 2018 Micro Minnie 2108DS.

Ray,IN · 10-29-2022, 04:13 PM

Well, 6V batteries connected in series DO NOT add amperage together, only voltage. If one 6V battery states 100A, when 2 are connected together you still have a 100A 12V battery.

Any battery that lists cranking amperage IS NOT a true deep-cycle battery, regardless of voltage designation.

Interesting reading: https://marinehowto.com/what-is-a-deep-cycle-battery/

Marine359 · 10-29-2022, 08:39 PM

Be careful of adding two 6v GC batteries to your 2108 tongue. Hopefully you are aware they are VERY heavy. And that needs to be taken into account with balancing your 2108 weight distribution. If your tow vehicle is a 1/2ton or mid-size, the extra weight of the GCs could overload the TV Rear GAWR. Might not be an issue if you don’t carry heavy stuff in the pass-thru, or if you counterbalance by adding a rear hitch receiver with bikes or generator.

**creativepart** · 10-30-2022, 08:29 AM

Golf Cart (6v) batteries do not always have a Group size. If you buy two GC batteries that have 230Ah each connecting them in series will give you a 230Ah 12v battery bank. That’s absolutely true and 230Ah 6v batteries are quite common. So yes, your info is correct.

As pointed out, weight will be a serious consideration, as those batteries are typically quite heavy - like 75lbs each. And charging them with your stock converter will likely take days, not hours.

Lastly, CCA or cold cranking amps mean absolutely nothing when buying deep cycle “House” batteries. Don’t even look at those numbers.

**creativepart** · 10-30-2022, 08:36 AM

Quote:

Originally Posted by Ray,IN

Any battery that lists cranking amperage IS NOT a true deep-cycle battery, regardless of voltage designation.

I’ve found that nearly all battery spec listings of all kinds of batteries feature (require?) CCA ratings as a matter of course. So, manufacturers are obliged to include them.

Morich · 10-30-2022, 05:46 PM

Some basic terms that may help cut the chase?
CCA--how much power you can get out quick,so that is more related to how well it may start a big engine. More CCA for an 8-10 cylinder engine than a 4!

Battery Group- A way to describe the size/shape of a battery without going into details of height, length, width. A size 31 will replace a size 31 without having to look at how big?
Amp hours? Big thing to look at once you find what size fits the space! Like how many gallons in the bucket? If you have a specific spot to put the battery like a battery tray, go for a size that fits or can be modified, then go with the largest number of amp hours.

There are details to how we each use those batteries that can change what works best for each.
If you want to go without plugging in to recharge, lean heavy toward the best amp hours and how far they can be drained without damage. Sometimes going to some of the newer types can fit, even when they cost considerably more.
But if you are more inclined to almost always be hooked up to power, there may not be that much advantage to going expensive when they rarely get used enough to go down very far and the cheap deep cycle "hybrid" used for things like fishing trolling motors can be a better value. They are used for both the trolling "deep cycle" as well as starting the engine. But they are so much more common that we may find them much cheaper!

Prospects of how long you plan to keep the RV can also enter the process. If you only see using the RV for 3-4 years, it may not be good economics to buy $600 of batteries and a $1000 to retrofit the power to last ten years!

BobC · 11-01-2022, 06:28 AM

As Marine359 posted, tongue weight can be a critical factor. One solution is, rather that go the golf cart battery route, two 12V 100Ah AGM true deep cycle batteries (in parallel) would allow you to mount them inside your forward storage compartment. This will give you 200Ah.

Marine359 · 11-01-2022, 10:21 AM

A don’t believe there’s much weight difference between a 100ah 12v AGM and a 230ah 6v GC. However, as Bob C mentions, some people feel comfortable mounting AGM in their pass thru. Opinions differ on that, but I decided not to do that because manufacturers of AGM batteries all state that AGM must be mounted in a vented location. Although rare, and I’ve never even heard of it happening, glass mat batteries can off-gas if overcharged. That’s why they have a vent built right into the battery. The vent is there to allow the battery to off-gas without exploding. I felt uncomfortable with that situation considering the head of our bed is right above the pass thru. That left me with the one alternative that was the most expensive option: Put a LiFePo4 in the pass thru that would give me the amp hours equivalent to 2x 6v GC, or 2x 12v AGM. Although the cost of LiFePo4 is now about the same as AGM, there are other additional expenses that add to the total cost of LFP. That is the cost of replacing the converter/charger in your MM with a converter that is compatible with LFP charge profile. You can go without a new charger, but you can’t use the full capacity of the LFP, so why bother. My single 170ah LFP weighs 47lbs. That’s about 35% of the weight, or at least a 90lb weight advantage versus two LA batteries. I’m not pitching LFP, if I could handle the weight of two 6v GC, I might have gone that way, but I would have needed a bigger truck with higher payload to handle the added tongue weight. If you have a payload of 1600 lbs or more, you’re probably good to go with 2x LA.

BobC · 11-01-2022, 01:56 PM

I was under the impression that the OP was planning on replacing a single 12V battery with the two 6v batteries, hence my concern about the weight being doubled or more.

Bobn1957 · 11-03-2022, 12:00 AM

If you can afford it, go with a pair of lithium batteries. They are way lighter and can be discharged more than lead acid's recommended 50% (a 230 Ah lead acid is effectively a 115 Ah battery) Discharging a lead acid battery below 50% will shorten its life dramatically and maybe even kill it! If you go with lithium, you will need a specialized charger.

BobC · 11-03-2022, 08:53 AM

Quote:

Originally Posted by Bobn1957

If you can afford it, go with a pair of lithium batteries. They are way lighter and can be discharged more than lead acid's recommended 50% (a 230 Ah lead acid is effectively a 115 Ah battery) Discharging a lead acid battery below 50% will shorten its life dramatically and maybe even kill it! If you go with lithium, you will need a specialized charger.

I agree that lithium (LiFePO4) batteries are preferable for someone who uses their RV frequently and frequently camps without shore power, however:

1. There's more to installing than the batteries themselves, meaning more $ than the battery price differential. You may need a new converter/charger for shore power charging and a DC-to-DC charger for alternator charging, etc.

2. Discharging a lead acid battery below 50% is only an issue if you routinely do so. Occasionally doing so won't have a perceivable effect. Discharging below 80%, regardless of frequency, can cause actual damage. There's an interesting discussion on this in the following IRV2 thread starting at post #22:

https://www.irv2.com/forums/f56/firs...-535245-2.html

In my case, I chose to go with AGMs instead of LiFePO4s primarily for the reason that I'm not using my MH that much. I'd hate to see an investment in LiFePO4s (including the additional costs in 1. above) waste away while spending so much time in storage. Were I to be using it more frequently with a reasonably high percentage of boondocking, I'd definitely go for LiFePO4s.

Despite their advantages, switching to LiFePO4 batteries isn't a no-brainer as many maintain. Everyone's use case is different.

Marine359 · 11-03-2022, 09:31 AM

If I had a motorhome like Bob, with plenty of CCC, no way I would have switched to LFP when 4x 6v GC gets the job done. Bob has plenty of CCC, and an absorption fridge. It really is a no-brainer to switch to LFP if all of the many advantages of LFP in your particular rig would far outweigh the cost consideration. Let me get this out front: the cost of installing LFP is almost irrelevant if you need to remedy the power situation in your rv to make camping more enjoyable, or to make multiple days of boondocking possible, when Lead Acid is not an option. It costs less than the fuel you’ll use on a single rv trip.

In my case, I have a TV with limited payload, so adding enough Lead Acid to the tongue to meet my boondocking needs was a definite no-go. Plus, since I wanted an inverter anyway, buying a hybrid inverter/charger was a very small incremental cost. It allows me to charge my battery almost 4 times as fast. I can now pump in 150 amphrs in less than 2 hours into my LFP. The LFP itself was almost cost equivalent to AGM.

People keep saying a LFP conversion is too expensive. Those are the people who know very little about the actual costs, because they never priced it all out like I did. Or, they are not DIYers, and have been quoted big numbers by repair shops. All told, including hybrid inverter/charger, battery, cables, etc., my install cost about $1,000 more than it would have cost upgrading to AGM (including inverter, transfer switch, and new charger). I HAD to upgrade because my rig came equipped with a 12v compressor fridge. So, yes, it was a no-brainer for me, but wouldn’t be for everybody. If you don’t believe $1,000 (incremental) is outrageously expensive to get near total freedom from DOD concerns and maintenance, and you want to be able to charge up in a hurry, maybe LFP should be in your future.

If you have ever quit smoking, you know how much better you feel, and how much healthier you feel, not to mention how much longer you’ll live. Same is true for LFP. Feels better, lives longer.

BobC · 11-03-2022, 10:04 AM

Jim and I are in agreement. I often forget that the world of Micro Minnies is drastically different than with motorhomes.

Even when I had TTs, they weren't ultralites and the incremental weight of two golf cart batteries on the tongue vs. a single "Marine/RV battery wasn't an issue.

Bobn1957 · 11-03-2022, 11:28 AM

Quote:

Originally Posted by BobC

I agree that lithium (LiFePO4) batteries are preferable for someone who uses their RV frequently and frequently camps without shore power, however:

1. There's more to installing than the batteries themselves, meaning more $ than the battery price differential. You may need a new converter/charger for shore power charging and a DC-to-DC charger for alternator charging, etc.

2. Discharging a lead acid battery below 50% is only an issue if you routinely do so. Occasionally doing so won't have a perceivable effect. Discharging below 80%, regardless of frequency, can cause actual damage. There's an interesting discussion on this in the following IRV2 thread starting at post #22:

https://www.irv2.com/forums/f56/firs...-535245-2.html

In my case, I chose to go with AGMs instead of LiFePO4s primarily for the reason that I'm not using my MH that much. I'd hate to see an investment in LiFePO4s (including the additional costs in 1. above) waste away while spending so much time in storage. Were I to be using it more frequently with a reasonably high percentage of boondocking, I'd definitely go for LiFePO4s.

Despite their advantages, switching to LiFePO4 batteries isn't a no-brainer as many maintain. Everyone's use case is different.

I did mention the need for a specialized charger, but the main reason I recommended the lithium option was the weight on the hitch and the fact you can draw the batteries down below 50% without hurting your batteries.

Marine359 · 11-03-2022, 02:43 PM

Thanks Bob,
We’ve owned several motorhome before the advent of LFP. As I think back on it, I wouldn’t felt a need to switch to LiFePo4 on any of them. The main reason is because LA were cheap, and when I was a working stiff, I was a battery abuser. 2x 100ah LA along with an absorption fridge was plenty of power for my family for a few days in NPs and SPs. Too busy to worry about a lot of maintenance other than the occasional hydrometer check. So, when they went south, I just bought new ones. That’s really the same case today. Even if you abuse your LA, it’s probably cheaper to keep replacing them every couple of years than to switch to LFP, especially if you don’t use your rv that often. Of course, if you’re a stickler for maintenance, you can stretch the life of those LAs to four or five years. A pretty good bargain.

Bobn1957 · 11-03-2022, 03:57 PM

A set of lithium batteries cost about the same as two sets of lead acid and last twice as long, lithium also tolerates long periods of storage.

Ray,IN · 11-05-2022, 06:46 AM

Quote:

Originally Posted by creativepart

I’ve found that nearly all battery spec listings of all kinds of batteries feature (require?) CCA ratings as a matter of course. So, manufacturers are obliged to include them.

Actually that is not true.. For instance, this is a true deep-cycle 12V battery, please show me where it even mentions CCA.
https://www.amazon.com/gp/product/B0...KIKX0DER&psc=1

**creativepart** · 11-05-2022, 08:43 AM

Ray, I said that “ I’ve found that nearly all battery spec listings of all kinds of batteries feature (require?) CCA ratings as a matter of course.“

Which is true, that’s what “I” have noticed. “Nearly” not all, not every, not every battery on Amazon. Not every battery in the world.

What “I’ve Found” is what I’ve found. A great many online data sheets for all manner of batteries provide a listing for CCA and other typical starting battery terminology. I, personally, do not think you can make a blanket statement that any battery that lists a CCA in its specs cannot be a true deep cycle. That’s what I meant, and in my experience I, personally, believe that is true.

You, on the other hand, are free to agree with that or not. As you are with every other opinion on this website. That’s how a forum works.