Which is the better battery configiration

[Campinfan]

I am trying to learn more about 6 volts batteries versus 12 volts. I know the 6 volts can be drained further and recharged more (better lifetime). At least that is what I think is true. But it seems 12 volts have more amp hours (or minutes) (I think). So if I got 4 batteries, would you get 4 12 volts and put them parallel or 4 6 volts and wire them in series to get 12 volts and then in parallel to double the amp time? And why? I may be venturing into the Motorhome world and I have many questions.

Thank you.

[Campinfan]

So Pianotuna, are you basically telling me that I could get a DC to DC charger and then that would take the starting (chassis) batteries and use them to charge the house batteries? And of course the alternator would recharge the starting batteries.

[pianotuna]

Campinfan,

The only dumb questions are the ones you don't ask.

[Campinfan]

Thank you Chris! I really wont be boondocking. I am just thinking I will use it when we are driving and want the fridge to run. I have never had a MH before so I am a newbie in this arena. My current rig is a fiver with a residential fridge and that was new to me too. I have had numerous trailers with gas absorption fridges and just ran them off propane as we drove to our destination. So I may be asking some really dumb questions...lol

[wa8yxm]

Campinfan wrote:
The reason why I say four of either is because I would have room for 4. That is why I have the question of 4 12 volts which would give me 4 times the amps of one....

With 4 of either I have to ask what size
GC-2 are about the same "Footprint" as Group 24 but taller.
So a box that fits 4 Group 24 (300 ah) would fit 4 GC2 Over 400AH

A box that fits 4 Group 31's (about 500 AH) would fit six GC-2's (or nearly 700 AH)

Plus the difference in minimum state of charge levels make the GC-2s way way better

Add to that the "Economy of scale" The GC-2 being the single most produced lead acid battery is of course the lowest price per watt hour.

[opnspaces]

Campinfan wrote:
The reason why I say four of either is because I would have room for 4. That is why I have the question of 4 12 volts which would give me 4 times the amps of one....or 4 6 volts which would effectively give me 2 12 volts. I hope that clears it up. If all things were even....I would have 4 x 12 volts @100 minutes a piece (just pretending here) so that would give me 400. If each 6 volt was 100, I would only have 200 because I know in series only the volts double not the amps but then they would be partially in series so then I would have the equivalent of 2 12 volt batteries @ 100 a piece for a total of 200. So it seems the 12 volt battery is a better idea until I think about how much lower you can drain the 6 volts.

Correct to a point until you look at real life. Typically unless you want to spend $400 per 12v you will find most 12v batteries are 75 to 90 ah. A typical 6 volt is 200 to 220 ah, so...


12v @ 75ah x 4 = 300ah or 4 x 90 = 360ah

You are correct that the 6v in series doubles only the voltage so

Two 6v @ 200 ah = 200ah. Four 6v at 200ah = 400ah.

Two 6v @ 220ah = 220ah. Four 6v at 220ah = 440 ah.

[pianotuna]

Campinfan,

Often there is little or no charging from the vehicle alternator to the house battery bank.

The solution that works for me is a dc to DC charger. I now get up to 20 amps of charging to the house bank.

However 20 x 12 = 240 watts. Depending on the duty cycle of the fridge, that may not be enough.

There are dc to DC chargers with higher capacity.

Do realize that alternators have a duty cycle too. I prefer to not exceed 1/4 of the alternator output.

[Campinfan]

I typed the above before I read all the above. Some of the comments are above my knowledge level but I think what Valhalla says is what I am looking at. Why am I looking at this????Well, I have a residential fridge now that is on an inverter. No solar or genny in my fiver. So it does pretty good running my fridge on the way to Florida or so, but then on the way home, my inverter quits (and I think it is due to an overtaxed battery) for the trip home. I really think the one trip pretty much kills the battery. If I get this MH I am looking at, I do not think it has solar but it is ready for it (it is a 2019 unit). I could use the genny to power it (I guess) but I just want to make sure I do not kill my battery. I have gone through 3 -4 batteries in my fiver and then the slides do not want to work right....I am thinking the battery gets drained too fast and then I have to stop, let it reset and then moves the slides 5-10 seconds at a time.

So I am thinking I will get 4 volts for the MH when the time comes. With Lithiums, do I need to get a different charger or something for them. This is the stuff I have no clue on or how hard it is to add a different charger or whatever I need.

[Campinfan]

The reason why I say four of either is because I would have room for 4. That is why I have the question of 4 12 volts which would give me 4 times the amps of one....or 4 6 volts which would effectively give me 2 12 volts. I hope that clears it up. If all things were even....I would have 4 x 12 volts @100 minutes a piece (just pretending here) so that would give me 400. If each 6 volt was 100, I would only have 200 because I know in series only the volts double not the amps but then they would be partially in series so then I would have the equivalent of 2 12 volt batteries @ 100 a piece for a total of 200. So it seems the 12 volt battery is a better idea until I think about how much lower you can drain the 6 volts.

[SJ-Chris]

Campinfan wrote:
I am trying to learn more about 6 volts batteries versus 12 volts. I know the 6 volts can be drained further and recharged more (better lifetime). At least that is what I think is true. But it seems 12 volts have more amp hours (or minutes) (I think). So if I got 4 batteries, would you get 4 12 volts and put them parallel or 4 6 volts and wire them in series to get 12 volts and then in parallel to double the amp time? And why? I may be venturing into the Motorhome world and I have many questions.

Thank you.

For just about all intents and purposes, using two 6v GC lead batteries in your RV house is better than using two 12v lead batteries. As long as they fit (6v batteries are typically an inch or so taller). If you were thinking about using four 12v batteries, four 6v GC batteries will be better. The 6v GC battery is better designed for deeper and more frequent discharges.

If you are not boondocking more than 40-50 days PER YEAR, and you have a way of charging your lead batteries soon after each discharge (ie. solar, generator, etc), there is absolutely no problem discharging them 80% each time. The "don't let them discharge below 50%" mantra is incorrect and a myth for 99% of casual RVers. If the above sentences describe how you will use your batteries, you will never "use up" all of your batteries potential total lifetime number of cycles and you don't need to worry about your batteries getting down to 20%. One caveat I would mention: If you use your inverter a lot and/or have heavy draws on it, then lead batteries WILL give you a problem as their State of Charge gets lower and lower. This is one area where more expensive Lithium battery solutions excel.

Lithium batteries are better than lead batteries for many reasons...And if those reasons are important to you in practice (not just in theory), then Lithium batteries are an amazing solution. BUT many many many RV users don't need Lithium batteries to enjoy their RVs/TTs to their particular requirements (ie. most casual RV users).

One last thing....If you are asking about batteries, I assume it is because you are interested in boondocking (not just being plugged in at a campsite). If that is the case, you will definitely want to consider some solar on your RV as that does amazing things for your RV experience as it pertains to batteries. It effectively extends your battery AHs...It means less generator running/noise...It means no dead batteries while in storage...It extends your battery life by never having your batteries sit drained...(all of this of course depends on sunlight availability).

Good luck!
Chris

[pianotuna]

w8yxm,

Thanks for the real life testing.

I love LiFePo4, but they don't love my climate.

[wa8yxm]

Standard 6 volt is the GC-2 give or take a bit it's 220 amp hours and when you put two in series it's still 220 amp hours (only now it's a single 12 volt battery electrically that is) Think 4D or 8D (Those suckers are heavy)
They can be taken down to 50% being true Deep Cycle before what I call "Rapid Aging sets in and if you do an OH CR** discharge (Say to 10 percent) Fairly good chance they will recover

Now 12 volts.. Starting batteries need to be kept full or close to it. Oh they can deliver a whole lot of amps often 2-3-4 times their AH rating but only for like 30 seconds.. But the total amp horus rating is usually less

Group 24 about 75 or less
Group 27/29 about 100 give or take 5
Group 31 130
So a pair of them 150 200 230

But with Starting batteries I'd limit discharge to around 20% of that or less
And do an OH-CR**.. stick a recycle sticker on it it's toast

With MARINE/deep cycle (Same capacities) around 25% or less

I've seen them recover from an Oh CR** but one.. IT was short term (Recharged quickly) and not many times. the GC-2s did a lot better.

Some folks talk about AGM batteries... Well I've not seen much improvement in battery anythign with AGM over Flooded wet other than you can mount them other than "This Side UP"...

LiFePO4 This is fairly new technology and I have a couple small ones for testing.

One is a 12 AH battery .. Can safely use at least 11 of 'em and unlike lead acid the voltage does not slide down (Kind of drops sharply near the end and though it does decrease as it runs down... It's not much of a decrease till the very end.

My test load is a 100 Watt ham transmitter draws 20+ amps at full power and really likes the LiFePO4 I also have a 10 AH one I've not yet tested with the TS-2000 (The radio) yet I did use it to power a freezer during a power fail. Nothing thawed.

The problem however is LiFePO4 takes a different charge profile so it is not always compatable with your converter or motor home / tow vehicle isolator.

You need some electronics added to the system to deal with it.

[valhalla360]

You will find that amp-hr are higher with 6v batteries even accounting for the voltage.

The big advantage is 6v are true deep cycle batteries. You will be hard pressed to find a deep cycle 12v battery. Trolling or dual purpose batteries are just rebranded starting batteries. You still don't want to pull them below 50% often or it will shorten their life.

[Matt_Colie]

Canpin,
After you get your arithmetic correct and look at the cost/life of each, then seriously going over to FeLiPo4 and the required hardware.
While I can tell you from personal experience that pairs of golf cart batteries will far out perform a collection of 12V jars, they still leave a lot to be desired.
Matt_C

[TenOC]

Four 12 volt = 8 (not 4) six volt.