6v or 12v?

[Freep]

All else being equal, which is preferable and why?

2 220 AH 6v batteries
or
2 110 AH 12v batteries

[azrving]

F450EC1165 wrote:

rjxj wrote:
You cant compare a 12 v gp dual purpose battery to a gc2. As covered in the last go around compare a Trojan SCS225 to two T105

How about two of the Trojan T-1275 Plus at 150 AH each?

Yes and maybe that's an even better example. Point is to not compare a common group battery to a common gc2. There is NOTHING wrong with a regular dual purpose 12 v gp. I have one 10 years old. Unbelievable value.

[time2roll]

Freep wrote:
I don't how the battery is charged now when the gen is running or when I'm plugged in. I do remember seeing some device in the basement wired between the gen and something. I'll have to check that out.

Post the converter model number for best suggestions.

[SideHillSoup]

Two 6 volt batteries hand down. Have had both two 12's and two 6's in a number of different RV's over the years and hands down the 6 volt batteries last long when using them. The 6 volt batteries cost more than the 12 volt and they also have a bigger plate size which as have also said others do better on draw down and charging cycles.
If I had the room I would be installing four 6 volt batteries.
Now I am only talking about useing the 6 volt batteries in my camper with a solar panel. For my boat I have one deep cycle battery.
A lot of my buddies with older RV's for hunting will use 12 volt battlers as they are cheaper to buy and they don't have solar systems, and run generators most of the time, so storage capacity of the battery doesn't matter to them. They also use 12 volt so they can interchange the batteries into different rolling stock they have ( cheap buggers... grin)
My truck charges the batteries while it is running and it's doesn't matter what batteries are in the camper as long as they are hooked up correctly.
We do mostly boondocking and have never had an issue with dead batteries since we went to 6 volt.
People can chuck a bunch of numbers out there but I'm going form years of experience only.
Soup.

[Daryl_B]

rjxj wrote:
You cant compare a 12 v gp dual purpose battery to a gc2. As covered in the last go around compare a Trojan SCS225 to two T105

How about two of the Trojan T-1275 Plus at 150 AH each?

[pianotuna]

Hi,

Since the current for twin six volts is going to be double that of twelve volt jars in parallel, there is MORE chance of plates warping from high loads. I do push my bank hard sometimes demanding nearly 200 amps. My highest recorded demand was 278 amps.

Positive plate shedding is impossible to reverse. The deeper the cycle the greater the shedding. Double the current and double the shedding. Eventually that will short out a cell in a flooded jar.

My longest lasting 12 volt jar was a marine battery that I used as a starter. I purchased it in 2004, and replaced it in 2016, not because it had failed but because it had started to exhibit corrosion around the posts.

If you are a weekend warrior, add some solar and the battery bank life will increase dramatically (if a decent charge controller is used).

Oldfordman wrote:
Biggest advantage to a pair of 6v batteries for a 12V system vs single 12V is the plate size in the 6V. It will stand up to more charge/discharge cycles as well as supply high currents with less plate damage.

[Kayteg1]

Per my experience Golf-cart batteries offers the biggest bang for the buck.
I bought 4 of them for my conversion and at Sam's they were very cheap, while lasted 12 years.
Now needing single battery for the camper, I just use one I removed from the car.

[pianotuna]

I prefer 12 volt, but "redundancy" is not one of the reasons.

Statistically the greater number of cells, the greater chance of having a failure. So a six volt pairing in series is less likely to fail than a twelve volt pairing in parallel, simply because the cell count is 50% less.

If a cell fails in a twelve volt pair, the remaining battery may be compromised rather quickly.

Here are my reasons for preferring 12 volt cases:

lower voltage drop on high loads

space limitations. My OEM compartment would fit only 3 jars--so a 12 volt form factor gave me 1/3 more capacity

Some long time members may remember I used to have 7 12 volt house batteries. Watering them was a chore, so I went to a lower total capacity with an AGM 12 volt form factor, when it was time to change.

If LI could be reliably charged in below freezing temperatures I would have considered it. Their very best attribute is they do not need to be charged to 100% on every cycle--in fact there is some evidence they do better if NOT taken to 100%

If I had deep pockets I would use the carbon foam jars from Firefly, or the Outback version of those. These share the attributes of LI except they can be charged in freezing weather, and they weigh in at the same amount as lead acid jars. These share the ability to not require 100% recharging--though it should still be a goal.

My ideal battery bank would be 2 volt cells with a capacity of 800 amp-hours wired in series.

[Oldfordman]

Biggest advantage to a pair of 6v batteries for a 12V system vs single 12V is the plate size in the 6V. It will stand up to more charge/discharge cycles as well as supply high currents with less plate damage.

If you have the room, ability to carry the extra weight, and a durable wallet, get the biggest 6V batteries you can.

That said, eventually all Lead/acid batteries will be kicked to the curb as the new battery technology takes over.

I drive a Chevy Volt with a 17 Kwh battery that weighs only 400#.

Can be charged with a 240v charge station in only 4 hours 5,000 charge discharge cycles versus maybe 500 for Lead Acid and only if you only use half the battery's capacity.

17 Kwh from the 400 pound battery versus 1.2 Kwh from a 100# battery. Put four of them together in any configuration you want and 400# of lead acid batteries will only provide a fraction of the capacity the Li-Ion battery pack in a Chevy Volt.

Obviously, the Volt battery pack uses higher voltage (360) but it's an example of what the future holds. Higher capacities, longer service life, less weight.

Maybe the alternative will be here before I have to replace my two 12v batteries connected to a selector switch.

[DWeikert]

GordonThree wrote:

cewillis wrote:
I'd rather have (and do have) multiple 12v. If one is no good, you're still in business. And with the specs you mentioned, it's 220AH at 12v either way.

X2 for 12v

X3 for 12v

I can always bypass a bad battery and still have a 12v system. In the absolute worse case scenario, I could use a house battery to start the truck. Much more versatile than a pair of 6v's, IMHO.

[azrving]

work2much wrote:

jimh425 wrote:
People are in favor of 6V for less cost for same capacity/durability. Disadvantage is that you need both batteries to power your system.

I have no reason to switch to 6V batteries currently since either system works for my purposes.

It's true but a decent battery that is maintained with proper monitoring and charging is a pretty reliable source of power whether it's a pair of 6v or a single 12v. These are essentially the same aside being connected by cables vs encased in a piece of plastic.

Could one 6 volt battery fail completely and render a 12 volt system unusable? yes, but I don't think it is any more likely than a 12 volt battery losing individual cells.

Again, if they are comparing group batteries to a common GC2 then it's more like that the group will fail before the gc2. To make a true comparison they need to compare a true deep cycle 12 volt which might be something like an Trojan SCS225 which is an expensive battery when comparing amp hour to amp hour. If gc2 wont fit than us gp and there is nothing wrong with them.

[work2much]

jimh425 wrote:
People are in favor of 6V for less cost for same capacity/durability. Disadvantage is that you need both batteries to power your system.

I have no reason to switch to 6V batteries currently since either system works for my purposes.

It's true but a decent battery that is maintained with proper monitoring and charging is a pretty reliable source of power whether it's a pair of 6v or a single 12v. These are essentially the same aside being connected by cables vs encased in a piece of plastic.

Could one 6 volt battery fail completely and render a 12 volt system unusable? yes, but I don't think it is any more likely than a 12 volt battery losing individual cells.

[jimh406]

People are in favor of 6V for less cost for same capacity/durability. Disadvantage is that you need both batteries to power your system.

I have no reason to switch to 6V batteries currently since either system works for my purposes.

[Oyabun]

I'm using a pair of 12v AGM's because they were given to me. I've considered 6v when the time comes to replace the 12v. How would I go about charging a 6v batteries when one goes south on the road?

[work2much]

I have spent considerable time looking at batteries over the last year. We currently have a pair of t-105 6v batteries run in series to produce 12v. as well as a second bank with 2 12v trojan 100 amp hour batteries. These 4 batteries produce about 425 nom. amps but in reality they produce about 200 amps if you are willing to drain them down to 50% which we don't. We try and stay above 12.3 volts all the time which gives us about 120 Amp Hours of service. This has been ok since we don't use much now and have a 500 watt solar array to help keep them in the top 70%. Our new camper we are looking to run and use more stuff.

We are going to bite the bullet with Lithium Iron Phosphate LiFePo bank. The batteries can be almost fully discharged so a 200 Amp (2 28 pound batteries) hour bank would give us more power and battery wight would be 1/4 of the weight of what we have now. Weight is an important consideration in a TC.

The high battery cost, about 900 bucks for a 12v 100 battery is offset somewhat at time of purchase in that you need half the number of batteries and further off set in that they can typically go 3x the recharge cycles. In the long run the can definitely pay for themselves if you take care of them. LiFePo batteries also can accept higher charge rates which means you can charge them more quickly.

"Drop in" versions have a BMS (battery monitor system) so for the most part you just buy the battery and drop it in as a replacement and it will work fine. The BMS controls the charging limits to the battery to protect it although with a quality solar and shore charge controller you can refine the charging settings to maximize the battery. You also need a decent battery monitor. LiFePo batteries have a pretty flat discharge rate in volts so a voltmeter is a poor way to gauge. Victron or Bogart meter is a wise investment and are fully configurable to these batteries.

Anyway, my 2 cents. We have been happy with our 2 6v golf cart batteries and looking at your usage they should work just fine. Take them out every 3 months or so to check water lever and test with a hydrometer. That has served us very well for almost a year full timing.

[pianotuna]

Hi,

Batteries are designed around a 25 amp per cell discharge rate. When that is exceeded there may be excessive voltage drop. If the voltage falls enough, then the inverter may cut out, even though there is still lots of power to be had.

Example:

If you have a 220 amp-hour six volt jar in series with another, then you have a 220 amp-hour twelve volt battery with six cells. If a load of 50 amps is placed on it, then each cell must provide 50 amps. There may be lots of voltage drop.

If you have two 110 amp-hour twelve volt batteries wired in a balanced manner, then you have a 220 amp-hour capacity but with 12 cells. If a load of 50 amps is placed on it, then each cell only needs to provide 25 amps. There will be less voltage drop than in the six volt twins.

I often do 70 amps loads, so having 4 12 volt jars means the load per cell is 70/4 =17.5 amps per cell.

My microwave draws 156 amps. With 4 six volt jars each cell must do 78 amps, but with 4 twelve volt batteries it is 39 amps.

I hope this helps.

Freep wrote:

pianotuna wrote:
It depends.

My own preference is 12 volt. I do that because I run a medium size 3000 watt inverter.

This is interesting. How does the inverter figure into this? At some point I'd like to add an inverter too. The hope is to one day be able to run the MW for a few minutes without running the gen.