12v vs 6v House Bank

[ranger58sb]

Originally Posted by Sailmonkey

Used to be blue seas......I believe the original supplier is still making them though under for a different label.

Box Battery GolfCart - Blue Sea Systems

Interesting, thanks. I see from that link they only offered these boxes for 8Ds, 4Ds, and GCs.

Too bad; wouldn't mind having boxes like that for our banks of 31s... although maybe the original manufacturer actually has more models...

-Chris

[s/v Beth]

I was going to ask about the boxes also. BTW nice work mainsail. Got any suggestions for caps/water maintenance systems?

[pacific_voyager]

Keep in mind that whether six or 12v the number of parallel strings will degrade the life of the battery bank. Some authorities estimate it at 40% per string. My recommendation is to have no more than two parallel strings (e.g. 2 x 12v or 4 x 6v).

The battery bank that will last 8-10 years (or more) is 6 x 2v cells to make up a single large 12v bank. 2v cells can be bought in capacities up to 1000AH.

I think that it won't be long until we will all be using LiFEPO4 batteries.

Cheers

Jeff

[sailor0516]

Originally Posted by Capt RonB

It all depends on the space vs capacity vs maintenance ... one 12v 8D size battery provides about 225 amp hours of capacity in a single battery that weighs about 175lbs ... two T105 6v batteries provide about the same capacity when wired in series and weigh 65lbs each. Much easier to wrestle in and out of the usual battery space.

On some boats access for maintenance is a real problem. In those cases you should consider Gel Cells or AGMs. These batteries are sensitive to charging voltages but they do not outgas (normally) and therefore terminals corrode less and you don't need access to add water. But pay close attention to manufacturer's charging specs. I had Gels in our last boat that lasted over 10 years and were still going strong when I sold the boat.

6V Golf Cart batteries at Sam's Club here in Florida were running under $100 each last time I checked. Hard to beat that

I have checked Sam's Club online, which battery do you recommend the "ultimate" lead acid or the AGM,
Thanks in advance
sailor 0516

[MarkJ]

Originally Posted by pacific_voyager

6 x 2v cells
Jeff

But remember if you are cruiisng long range you mightt not find 2 volt batteries in Ooonagalarby. Of a golf course either.

But in every country I have been to you find they have things called truck with big 12 v batteries

[Capt RonB]

Originally Posted by sailor0516

I have checked Sam's Club online, which battery do you recommend the "ultimate" lead acid or the AGM,
Thanks in advance
sailor 0516

The choice likely comes down to maintenance issues. If your batteries are in a place that's difficult to check the water or if your boat gets intermittent use and you're not there to keep a check on things every day, then AGM would be a better choice. They do require proper charging ... but if you follow the manufacturer's recommended cycling, voltages, etc they will likely last longer than the wet cells. I got 10 years plus out of my gel cells and they were still going strong when I sold the boat.

Wet cells are quite a bit less expensive and may last quite a long time but they will require frequent water replenishment and constant terminal watchfulness. This is because they outgas or 'boil' away electrolytes and the stuff that they emit is very corrosive hence terminals tend to corrode. So you need good access to the battery tops, good ventilation of the battery compartment and lots of WD40. Distilled water is preferred for topping up wet cell batteries.

One other consideration might be charging time. If you have enough charging current (amps) the AGMs have a higher acceptance rate and will charge quicker. Wet cells seldom accept more than 25% of capacity and that only for a short time. AGMs will likely accept up to 50% of capacity initially if you can provide that much.

Also the AGMs are much more tolerant of bumping, rocking & rolling, etc. than wet cells.

If you can stand the initial purchase price, I prefer AGMs. Over the long haul, they'll likely end up the more economical choice.

OTOH, If your boat is an interim step to something bigger in five years, then I'd probably go for the cheaper alternative.

[sailor0516]

Thanks for the info.
Sailor0516

[Maine Sail]

Originally Posted by Capt RonB

The choice likely comes down to maintenance issues. If your batteries are in a place that's difficult to check the water or if your boat gets intermittent use and you're not there to keep a check on things every day, then AGM would be a better choice. They do require proper charging ... but if you follow the manufacturer's recommended cycling, voltages, etc they will likely last longer than the wet cells. I got 10 years plus out of my gel cells and they were still going strong when I sold the boat.

Wet cells are quite a bit less expensive and may last quite a long time but they will require frequent water replenishment and constant terminal watchfulness. This is because they outgas or 'boil' away electrolytes and the stuff that they emit is very corrosive hence terminals tend to corrode. So you need good access to the battery tops, good ventilation of the battery compartment and lots of WD40. Distilled water is preferred for topping up wet cell batteries.

One other consideration might be charging time. If you have enough charging current (amps) the AGMs have a higher acceptance rate and will charge quicker. Wet cells seldom accept more than 25% of capacity and that only for a short time. AGMs will likely accept up to 50% of capacity initially if you can provide that much.

Also the AGMs are much more tolerant of bumping, rocking & rolling, etc. than wet cells.

If you can stand the initial purchase price, I prefer AGMs. Over the long haul, they'll likely end up the more economical choice.

OTOH, If your boat is an interim step to something bigger in five years, then I'd probably go for the cheaper alternative.

Please keep in mind that AGM batteries are not the same as GEL batteries. The life you got out of your GEL's is not atypical of well cared for properly charged GEL cells. This however would be a non-typical life for an AGM battery, in my experience.

Properly charged flooded batteries are very easy to care for and arguably more accepting/tolerant of improper use/charging etc.. where GEL and AGM are not very tollerant. If you know you may not be the best about getting the banks back to 100% regularly, or your charging voltages can't be adjusted, or you don't have the proper current to feed to them, then AGM may not be the best choice despite their many other benefits.

I service piles of banks of flooded cell batteries with zero corrosion simply because the terminals were properly treated with a good terminal grease and the battery compartment has adequate ventilation. Terminal corrosion should be a non-issue with properly charged, installed and cared for flooded batteries.

Last Friday I was on-board a boat I re-wired nearly 5 years ago. It had recently been sold and my name given to the new owner. The "issue" turned out to be a loose nut on the battery terminal. The boat yard had negated a lock washer and the nut came loose....

The flooded cell batteries looked as good as the day I installed them, zero corrosion, and they still tested at about 95% of new capacity using a Midtronics analyzer. This is not bad considering the boat only has a stock alternator and a 15W solar panel.... The entire bank cost well under $300.00.....

This spring I replaced four 6V Lifeline batteries (old ones are still sitting in my shop for core) at four and a half years old. The previous bank of 4 GC2 6V wets had lasted 9.5 years on the same boat under the same owner with the same charging system. In both cases charging parameters had been set up to manufacturers specifications.

The flooded bank cost one quarter the price of the AGM's and outlasted it by more than double the service life. He still chose to stick with AGM, because money is a non-issue to him, and he wants the acceptance rate AGM offers. He was still not happy with the life and now has finally agreed to "condition charge" his new bank of Lifeline's to hopefully help it last longer..

AGM's certainly have benefits over wets but cycle life is just not one of the benefits I have observed in the marine environment..

[MarkJ]

Originally Posted by Maine Sail

Properly charged flooded batteries are very easy to care for

Not true in many, many installations.

Many new boats finding the batteries is a half day exercise in destroying the aft cabin.

To get at mine you must remove all the bedding and both mattresses from the aft cabin - and that cabin is the 'garage' so I have to remove all the junk as well.

Batteries are only easy to care for if they are checkable without fuss. So easy they can be checked often whist cruising.

So for people thinking about it look to see how easy it is to jump in there and top up some water on a weekly basis.

[Capt RonB]

Here's a cost comparison by a seller of AGMs fwiw
Cycle Life Cost comparisons between Flooded, AGM and Gel batteries | Discover Energy

[Maine Sail]

Originally Posted by MarkJ

So for people thinking about it look to see how easy it is to jump in there and top up some water on a weekly basis.

Weekly basis???? Something is drastically wrong if any flooded batteries on a boat need water on a weekly basis.. I have a customer who just recently completed the Great Loop, on a power boat, and his 6V bank needed water all of three times in thousands of hours of solar and alternator charging.. Also if the batteries are that hidden hydro caps can be had for very short money...

[MarkJ]

Originally Posted by Maine Sail

Weekly basis???? Something is drastically wrong if any flooded batteries on a boat need water on a weekly basis.. .

How often do you recommend they be checked?


Mark

[Maine Sail]

Originally Posted by Capt RonB

Here's a cost comparison by a seller of AGMs fwiw
Cycle Life Cost comparisons between Flooded, AGM and Gel batteries | Discover Energy

What a load of, well you know... $450.00+/- in service & materials for flooded batteries over 3 years?

I can tell you what my actual costs were over 7 years with flooded batteries.

$1.29 for a single gallon of distilled water. In seven years my bank of three group 31's took less than 1 gallon.

Perhaps 30 minutes total each year for checking water levels & refractometer testing.

About 15¢ for terminal grease which was only applied twice in 7 years..

I recently installed a 450Ah bank of four 6V GC2's that cost $348.00

The Lifeline bank of four 6V GPL-4CT's (440Ah) ran $1500.00

That lifeline bank will require equalization charges just like the flooded batteries and they will very likely not last as long.

You can check water levels quite a bit before you make up that price difference..


All batteries should be checked on a regular basis, loose terminals, bulging, etc. etc...

On boats with impossible access AGM's can certainly be beneficial but it will cost more not less. In the piles of vessels I work on I have yet to recall any situation where AGM's beat flooded batteries in a $$/Ah/cycles in a real life/real world cycle equation. The only time I have ever seen AGM's beat flooded batteries on a $$/Ah/Cycles equation is on the internet..

I think most of us can remember when the AGM makers used similar numbers to lie to us and tell us these batteries were good for 80% DOD.. They now suggest 50% DOD just like flooded batteries..

Lifeline:

"For maximum battery life in cycling applications, do not discharge the battery bank below 50%. Discharging the bank repeatedly to 100% will shorten the battery life."

Trojan:

"For optimum life and performance, we generally recommend a discharge of 20 to 50% of the battery’s rated capacity even though the battery is capable of being cycled to 80%."

Deka/East Penn:

"Using a 50% depth of discharge (versus 80% or 100%) will dramatically extend the life of any battery. Therefore, when helping to specify a battery for a system, choose a battery with at least twice the capacity required for best performance."

Rolls Battery:

"Do not completely discharge a deep cycle battery if it can be avoided. The deeper the discharge the less life you will obtain from the battery. The ideal method of operation in to charge and discharge the batteries through the middle range of their capacity (50% - 85%)."




I have LiFePO4 so no real dog in this fight I just do not believe, nor have I seen, AGM's be the panacea many make them out to be. If I was to ever go back to an LA battery it would be GEL or flooded for a house bank.

[sailorboy1]

I abused my bank of 4-6V golf cart Dekkas for 2 years (do a CF search). Those batteries are still on the boat working just fine and acturally seem (are) better than when new as far as maintaining a voltage. All it took was a solar panel to get and keep them charged.

Far as water goes I checked mine the other weekend after a month of pretty high temps and they were maybe 1/8" low after 3 months of use and I didn't add any. I think I've used maybe 2 cups of water in 2.5 years. It did seem to make a big difference when I changed the solar absorption time from 60 minutes to 30 minutes.

So I don't think I'm going to check my water more often than every 2 months from now (mine are pretty easy to get to). I think that each boat needs to determine how offen to check the water based on history as I bet the the way the batteries are used etc. determines the watering requirements.

When I chose to use the 6V a couple of years ago it was based on cost and weight.

I ain't no expert but everything I read over the years indicated to me than the 6V batteries were just a better way to go and the only small disadvantage was a couple of extra cables needed.

[sailor0516]

6volt vs 12v house bank. I read 2 6volt is better than 1 12v. but would (2) 6 volt be better than 2 12v in a house bank. Cost, size, weight not withstanding. It would seem 12 v would be better if amps are same?
sailor0516
(battery novice)