6volt or 12volt battery bank?

[Xinterface]

Morning folks!

First time poster but been watching over these forums for about a week now. They're is a tremendous amount of info here and I'm soaking it all in! I'm going to be starting my 7x16 v nose ct project when it warms up a bit so I'm throwing my plans together now. This will be a full-time living quarters so I must sure i do this properly. I am extremely excited to get started on this project!

My first question, of many, is the battery bank. I've watched tons of YouTube videos on venting, the proper amps that should be used for what you're going to be using it for. But I still have a lingering question. I see a lot of people use 6 V batteries over 12 V batteries in the battery bank. Are the deep cycle 6 V batteries capable of more amps when wired in series, making them 12 v. I know it all depends on 6 V battery you buy of course. Are they using them cause there cheaper? I'd love to hear your guys/gals insight.

Thanks,
Joe

[lrrowe]

I will leave the technical aspects to our more knowledgeable members who will respond, but from all my studies and research, as long as I am going to get a Lead Cell battery, I will be adding four 6V batteries to my 6 x 14 project.

[Bill n Robi]

Bookmarked this as I am interested also.
I have two brand new Interstate Deepcycle series 24 in my TD - I figure in two to three years I will be replacing and made the toolbox large enough to support 4 6V or maybe a Lithium bank. I am interest in the physical size and any issues charging them. Are there issues if one goes bad and you only replace one of a four battery set?

Any special considerations for a solar set up with 6 volt banks?

Thanks

Bill

[abqlloyd]

In theory there is no difference. Golf cart batteries are often used because they are designed for repeated charging and discharging and their lead plates are often thicker than the 12v counterpart. They are often less sensitive to voltage drop when out in series. Four 6v in series provides 450ah total, or 250ah at 50%. But the power is spread across multiple cells and multiple batteries. A large amp draw on a single battery can result in a quick voltage drop which can fool inverters into shutting down.
There are other advantages: if one cell dies, you replace one battery.
They are pretty robust if kept at a decent temp and watered when needed.
They are cheaper because they are mass produced.
No difference when charging with solar. Standard charge profile.

[abqlloyd]

Take a look at the weight of a single 6v battery. Multiply times 2. Now compare to the weight of 12v batteries in parallel to provide the same amp hours. The six volt batteries will be about 25% heavier than the 12v for the same amps. More lead = better battery life and performance.

[Xinterface]

Thank you guys. Appreciate the comments!

[bdosborn]

Four 6v in series provides 450ah total, or 250ah at 50%.

Not quite.

Batteries in series - The same AH no matter how many batteries are in the string but the voltage goes up by the battery voltage *N (N= # of batteries). 4 GC batteries in series would have a typical AH rating of around 225 and would be at 24V.

Batteries in parallel - The AH goes up by the battery AH*N but the voltage remains the same no matter how batteries are in the string. 4 GC batteries in parallel would have a typical ah rating of 900 and would be at 6V.

Two GC batteries in series and then paralleled with two GC batteries in series would have a typical AH rating or 450 and would be at 12V.

A GC battey weighs around 65# so that's why you don't see a lot of them in tears. Most people don't need that much capacity and don't want to add 260# to their teardrops. I used a single 12V battery in the teardrop and it worked fine. The second trailer has a 12V fridge and satellite TV so I needed the additional capacity of two GC batteries. It's all about how much capacity you want and GC batteries are usually cheaper then 12V deep cycle batteries if you need more capacity than a single battery.

Bruce

[bdosborn]

Any special considerations for a solar set up with 6 volt banks?

Nope, it's just looks like a big 12V battery to a solar controller.

Bruce

[abqlloyd]

You're correct and I misspoke. I have 4. Two pairs in series and then the pair in parallel for 12v. Good catch.

[bdosborn]

How many days can you go without shore power on 4 batteries? I think I can go about 3 days on 2 batteries with the 12V fridge on and watching movies at night.

Bruce

[abqlloyd]

With 300 watts of solar in NM I'm pretty sure I could go forever running the dorm fridge and lights and other electronics. I have another panel which I'm going to pull off as I simply don't need 600 watts on the roof.

[abqlloyd]

The advantage of four batteries was the ability to run the 2000w sine wave inverter without any overload. I've played with batteries and inverters for years. A single 12v can't hack the initial surge and the voltage drops below cutoff. Two 12v AGM 31's worked well but at twice the cost.

Get some big wire to the inverter and keep it short as possible.

If I could make one change it would be a 24v sine wave inverter to keep amps down.

[bdosborn]

I'm like you, I can go as long as the sun shines with the PV panels.



Bruce

[MtnDon]

6 volt golf cart batteries are more robust than virtually any 12 volt battery. Most of us run 12vdc systems so we need a minimum of 2. For the money they are a pretty good deal. You need to do some estimating of the needed battery capacity if you plan on much power use w/o being plugged in to the grid or running a generator a lot. If power needs require more than 2 golf cart batteries I suggest a look at LFP batteries. Many advantages such as light weight.... but a heavy weight when it comes to price. Do some research. They are not everyone's cup o' tea.

[dustboy]

My understanding was that using 6V batteries allowed you to run a pair in series. Correct me if I'm wrong, 2 12V batteries in parallel will always have one weaker battery, and the weaker one will draw current from the stronger, resulting in premature failure. Same issue as leaving your trailer battery connected to the tow vehicle battery when the alternator is not charging.