wiring (3) 6V Batteries to 12 V system

I would like to upgrade my house bank to (3) 6V batteries. I would love to do (4) batteries, but 3 is all I can fit. Can I wire 2 batteries in series and add a 3rd in parallel? I this Practical?
If this is possible, I'd really appreciate any advice on how to correctly wire this setup.
Thanks!

Do two parallel (one big 6 volt) and then series that duo to the third.

Nope. Won't work. Can series two and parallel to another series pair. The third is useless.

If you parallel two then series to the third, the third will not match the charge/drain rates needed for the others. Short life results.

Use two or four. Or six. Need even number.

Yup, that third battery will be completely useless. A series parallel setup will always be limited by the single battery in series.

Ken

I agree with the above comments. But there is one way that will work with three batteries:


Hook two 6v batteries in series and then hook a 12V battery in parallel. Not the best situation due to the mixed battery/connections situation, but in practice, ok. The problem will be finding a true deep cycle 12V battery.


It will be easier with AGMs as there is little difference between an AGM starting battery and a deep cycle one. But in that case you are probably better off just hooking three 12V Group 31s in parallel.


David

Sounds like you're trying to fit 6V golf cart batteries in an 8D battery box. A battery bank should have same size batteries of similar age and condition. If you're trying to pull 12V out of 6V batteries, it needs to be done in pairs as some have stated above. Each pair provides 12V in series, then each pair is paralleled with another matching pair. Anything else will result in wasted capacity and/or early demise of the bank.

Ski in NC said:

Nope. Won't work. Can series two and parallel to another series pair. The third is useless.

If you parallel two then series to the third, the third will not match the charge/drain rates needed for the others. Short life results.

Use two or four. Or six. Need even number.

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I stand corrected (and most certainly acknowledge Ski's expertise in the matter).

FlyWright said:

Sounds like you're trying to fit 6V golf cart batteries in an 8D battery box.

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I have that exact problem starting tomorrow. I think I am going to parallel two small 12V GC batteries in there. Is there a better option? Local repair guy insists he is right by saying I should NOT put deep cycles in and plop another 8D back in there. (there are two others in there too) Since I think it is important to have a proper house bank of deep cycle batts, I feel I am right. Am I? Are there any other options that I am missing?

Not sure what size space you're working with but these 6-V US AGM 305 floor machine batteries are the same width as a T105 golf cart battery, 1.3" longer and 3" taller. They deliver 312AH per pair. I'm installing 8 of them in my house bank for a total of 1248 AH. They have non-AGM FLA models as well up to 340 AH per pair. No affiliation.

U.S. Battery | Leader in Deep Cycle Batteries | US AGM 305 - U.S. Battery | Leader in Deep Cycle Batteries

Here was my adventure in golf cart batteries:


http://www.trawlerforum.com/forums/s4/6vdc-golf-cart-battery-question-17616.html

When purchasing batts you get service life from the weight of lead.

You might find the 12v 8D (in deep cycle ) does weigh more than 2 golf carts , and would make the best choice.

Getting it down the dock, is why they make kids.

Angus99, I had great service out of a set of 4 traditional flooded US Battery L16s, a bit taller than those delivering 425AH each. Look forward to seeing how your AGMs do.

Tom B "throw in" where? House bank, starter bank? If the latter, I'd stick with an 8D; a good one will have about the same or better AH as the GCs and better cranking characteristics and fewer connections, which is likely why the mechanic recommends that route.

Mike, you might examine whether non-traditional mounting orientation is possible.


AGMs, for instance, can be mounted sideways... so maybe there's a way to stuff 4 6Vs in there if you experiment with that.


Or... if you're mostly constrained by the horizontal size of an existing battery box (for an 8D, for example)... maybe there's just slightly enough room around that box so that a new and slightly larger box could handle 4 6Vs.


And then as Angus also mentioned, there are about 3 different sizes of 6V batteries... The "standard" (like a Trojan T-105) usually gives about 220 Ah/pair, and the two larger sizes go up from there. Of the two larger sizes, one is same footprint but taller, the other (L16) is physically larger all over. (All this from memory, check the Lifeline and Trojan sites for typical specs.)


-Chris

Tom.B said:

I have that exact problem starting tomorrow. I think I am going to parallel two small 12V GC batteries in there. Is there a better option?

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Two 6v in series is preferable to two 12v in parallel.
Benefit is in ability to charge fully \ consistently.
Should be lots of articles out there w a Google search

djmarchand said:

Hook two 6v batteries in series and then hook a 12V battery in parallel. Not the best situation due to the mixed battery/connections situation, but in practice, ok.

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That will work.

Make sure you get real deep cycle 8D battery's, it seems only two company's make real ones, the rest are just labeled as such but are not.

What Is A "Deep Cycle" Battery? Photo Gallery by Compass Marine How To at pbase.com

FF said:

When purchasing batts you get service life from the weight of lead.

You might find the 12v 8D (in deep cycle ) does weigh more than 2 golf carts , and would make the best choice.

Getting it down the dock, is why they make kids.

Click to expand...

"Not sure what size space you're working with but these 6-V US AGM 305 floor machine batteries are the same width as a T105 golf cart battery, 1.3" longer and 3" taller. They deliver 312AH per pair. I'm installing 8 of them in my house bank for a total of 1248 AH. They have non-AGM FLA models as well up to 340 AH per pair. No affiliation."

Angus

Good addition for those wanting AGMs.

When not at the dock how will the new AGM batteries get recharged - size and model of alternators or genset via inverter or both or ??

Also where in your ER will these be mounted?

Of the two larger sizes, one is same footprint but taller, the other (L16) is physically larger all over.

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The largest Trojan L16 is an 1 1/4" longer than their GC2, 1/8" narrower and almost 6" taller. The 305 are the same footprint as an L16, but shorter. Since height wasn't an issue for my inverter bank, I really liked the L16 format. I got a nice purpose built box that holds 4 from Dyno Battery in Seattle, via Fishery Supply.

I bought my "wet" (lead acid) 6Vdc deep cycle batteries at Costco. They are just as good as the Trojans but for less cost. I paid $83 each and I have 8. AGMs are much more $$$ and really don't last any longer than the lead acid batteries, so long as you maintain them on a regular basis.

Alaskan Sea-Duction said:

I bought my "wet" (lead acid) 6Vdc deep cycle batteries at Costco. They are just as good as the Trojans but for less cost. I paid $83 each and I have 8. AGMs are much more $$$ and really don't last any longer than the lead acid batteries, so long as you maintain them on a regular basis.

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In my experience, the Costco GC2 batteries are nowhere near as robust as the Trojans. The Trojans will take abuse that has the Costco (which I believe are Johnson Control) batteries crying uncle. Just look at the weight difference. Lead is everything.

That being said, I replaced the Trojans that came on my sailboat with Costco batteries this time. While the Trojans are undeniably better, the difference (in my probably deficient math) doesn't justify the price premium.

Where the difference really manifests is out on the hook, where it isn't (wasn't) practical to fully recharge. Most cruisers were running between 50%-85% SOC on a daily cycle. Now, however, solar panels have come down in price and up in efficiency enough that most modern cruising sailboats are able to fully charge daily. That's significantly less wear and tear on the batteries, so it isn't as vital to have the thickest plates available.

I could buy the Costco batteries and more solar for the same dollars as the Trojans, and use less charging fuel. Seemed like a pretty easy decision.

I don't know about Costco as we don't have one here, but Sam's has GC-2 branded Energizer and they are made by East Penn in this part of the country, they are very close to Trojan's quality wise by all reports I have seen.

What I learned is some places have a flat rate core charge (Sam's, Walmart) of $15 but the CG batt's will yield $25 at several battery shops (more lead then car battery) so I pay the core one place and return them to another and make a bit of profit.

I think you will find the Sam's Club Energizers to also be a Johnson Controls product. They are a great product, popular in these parts.

Lead-Acid Battery Manufacturers and Brand Names List 2015

For some rason, I thought the Costco batteries were Interstate. Are those also Johnson Controls in heritage?

FlyWright said:

For some rason, I thought the Costco batteries were Interstate. Are those also Johnson Controls in heritage?

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They are. Interstate is a marketing brand that doesn't manufacture themselves but resells JCI. They (JCI) are the largest battery manufacturer in America, and their stuff is sold under lots of different marks.

It's been a couple of years since I bought mine, and given that Costco is basically a consignment store, I hit up Google to see if anything had changed. Apparently some stores have gone from Kirkland badged batteries to Interstate badged. It's still the same battery made in the same factory.

While it may not be the highest quality battery around, it's still a very good one and the best bang for the buck. I'd go Costco again (although hopefully I won't have to any time soon.)

caltexflanc said:

I think you will find the Sam's Club Energizers to also be a Johnson Controls product. They are a great product, popular in these parts.

Lead-Acid Battery Manufacturers and Brand Names List 2015

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I was wrong the batteries I have are Duracell if that makes a difference.

Two years ago the batteries Sam's sold were made by East Penn, I verified this by calling them and was told this to be the case. I bought 8 of them at this time and they are performing well. I do understand that this is an "up for bid" item and as you showed they may be now made by JCI and have the Duracell label stuck on them.

I don't believe there is much difference in then and as you stated they are a respected name in batteries. I would have no problem purchasing JCI.

Thanks for the information.

caltexflanc said:

Angus99, I had great service out of a set of 4 traditional flooded US Battery L16s, a bit taller than those delivering 425AH each. Look forward to seeing how your AGMs do.

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Me, too, George. We're out of the water until Spring getting the steering rebuilt and a number of other things. Another guy I know used L16s on a similarly laid out ER to mine with great success. I wanted to maximize space above for other stuff.

sunchaser said:

Angus

Good addition for those wanting AGMs.

When not at the dock how will the new AGM batteries get recharged - size and model of alternators or genset via inverter or both or ??

Also where in your ER will these be mounted?

Click to expand...

Sunchaser, we have a Westerbeke 12.5 KW genset, which we're going to supplement with solar. I'm also upgrading the alternators to 100-amp units and adding new Balmar smart regulators, Centerfielder and Digital Duo. I've also installed a Magnum 2812 inverter charger. The system should be pretty flexible when we get through.

The original battery banks used to be outboard of the main engines (tiny white blocks in the drawing), and they were the only thing I did not like about the ER layout. They blocked access to one side of each engine and you had to be a gorilla reaching over an engine to remove the two 8Ds that were on each side.

The new house bank will be on the platform behind the port engine. These platforms are very robust--the starboard one holds the 720-lb Westerbeke and I consulted with the Defever builder, Wilson Lin, before deciding to put the 840-lb house bank on the opposite side. The new location is also closer to the centerline.



I reinforced the platform still further and the wall beside it. Then built a grid of oak 1 X 1s to keep the batteries in place. (The water heater is in a temporary location.)






The reinforced lid will press down on the top of the battery housings (NOT the terminals) with the downforce coming from turnbuckles. The lid will also be affixed to the wall. I know a guy who did his house bank this way and it works well.



This is as far as I've gotten so far with 4 of the 8 305s in place. The water heater is now lower and wall-mounted to accomodate the Magnum.

Angus

Good work and thanks. Our ER layout is similar with your original. Except we have 4 T105s per side resulting in 2/3 or so the house bank capacity compared to your new setup. I can only imagine the gorilla work with yarding the 8Ds around.

We haven't seen the need for solar panels but can see the gain if spending lots of time at anchor. Our journey's tend to be more engine op hours per day maybe and seldom stay at anchor more than one night. To whit, our main engines have 3 times the hours of the genset's.

That's interesting, a friend of ours with that same Defever hull did virtually the same exact thing in that very same location. Same inverter too! He used Full River AGM L16s. He also installed a large solar panel set up, and has been very happy overall with the results, having cruised the boat extensively.

Nice job Angus.......

Thanks, guys.

George, I'm pretty sure your friend (SG?) is one of my mentors. His Defever 44+5 has a very similar layout and he's done some really innovative work with his systems. His house bank and solar install are things of beauty from the pictures he shared. Great guy who's been really helpful to a neophyte--as so many on the TF and Defever forums have been.

My next challenge will be hooking up all these new components. I plan to work with the electrician at Worton Creek to plan the install and have him double check my work. I'd like to do all of the work I can with a goal of making it safe, functional and as close to ABYC standards as possible--the latter for any future insurance surveys.