6v verses 12v batteries

[Bob S]

I know this has been discussed at length before but was curious as to opinions.
I have room for (2) 232ah 6 volt US Battery #US2200 or (2) Group 27 # 27TM 105ah 12 volts under the starboard settee.

I know if a cell dies in the 12 volt set up I loose one battery the other is still good. If I loose a cell in the 6v set up they are both useless. Has anyone had this happen? I think the cycle life is better on the 6v and the price is almost $100.00 per battery cheaper.

Bob

 

[Roger Long]

This has started long flame wars in other venues but I would never have free acid wet cells in a sailboat. I've seen the results of two battery explosions one of which was disconnected and went off just as a friend set it down on the deck after removing it. Salt water and battery acid make chlorine gas, just what you don't need after a knockdown.

It may be true that you can get better performance from wet cells if you become a battery hobbiest and are willing to crawl around on top of them with safety goggles, hydrometers, and bottles of distilled water. I don't think the slight gain is worth the hassle.

When I designed this three plus milllion dollar boat:

http://home.roadrunner.com/~rlma

the detail electrical system was by an electrical subcontractor who does both marine work and a lot of things like back up power systems for utility and telcom switching stations. I asked what kind of batteries they proposed and they said "AGM"

I said, "For the safety?"

They said, "No, for the performance. The safety is just icing on the cake."

I've had the same AGM's in my boat since I bought it in 2005. They are almost twice the price but the difference is insignificant in the cost of boat ownership. There are cases of their exploding but with no free hydrogen and plates physically separated by fiberglass mat, it is far less likely. You really have to abuse them to have a problem.

My alternator is a standard unit. These batteries can be charged just like wet cells. It was the now uncommon gel cells that needed special chargers.

 

[Mike B]

Just look at the amp hr capacity. The 6Vs will deliver more power vs the Grp27. I replaced a 4D with 2 T105 6Vs and was very pleased with them. They held up and recovered much better than the 4D.
Mike

 

[Ed Schenck]

AGMs here too.

Have to agree with Roger. Install 'em and forget 'em is my motto.

My gels did well for over seven years. They were still OK but when I planned my cruise from Erie to ? ? ? I decided it was time to replace. I already had a 900CCA AGM for the starter. Now I also have four AGMs for the house that should be good for at least eight more years.

Strap them down anywhere, no boxes required. I have one in the bilge to free up some locker space. Life(battery) is good.

 

[Stu Jackson]

Oh, NO, not again

See: http://www.c34.org/projects/projects-battery-selection.html which is one of thousands of discussions about batteries. If you use wet cells, you get a bigger bang for your buck for amp hours in 6V. Stuff DOES happen, but the cells going out is far from usual if the banks are kept properly, treated well, charged properly, you know, all that stuff. If you go to different chemistries, there are other options.

However, if you actually cruise, and have refrigeration on board, you really to start thinking about a bigger house bank of at least 400 ah (4 six volts) to cover your energy budget, you have done one, right?

What do I have? 3 Grp 31 130 ah and a separate small emergency reserve bank of 60 ah. Many of our members have 4 six volts with separate reserves. I've installed 4 six V in many of my friends C34s, and we simply do't have room in my battery compartment because of earlier electrical work and fuses that would require a lot of extra effort to move, but it could be done. Maybe next time, but 360 ah is pretty close to 400 or 440 out of 4 six Vs. I can still hang on the hook for two days without charging and run everything with about 100 ah per day draw.

 

[Maine Sail]

Yes the life cycle is better on 6V batteries and they are significantly less expensive. A basic set of the GC-2 size 6V batteries will generally have a 20 hour rating of 220-225 amp hours while the group 27's will be about 210 when combined. I am a huge fan of 6V batteries and have yet to see a wet cell explode. Almost every boat I worked on, sailed on or delivered growing up used wet cells. While I'd personally love to have a nice 450 ah capacity bank of 6V batts I can only fit three so at this point I run three 12v batts.

The big benefit, for me, with AGM's is their ability to accept a charge faster. Do I use them? No I have never seen the need and get plenty of life out of my wet cells.

The battery core exchange pallets at both Hamilton Marine and Battery World show that AGM's are clearly susceptible to failure as I witness quite a few of them and when I do I glance at date codes. Just about a month ago there were four AGM's, all different & not necessarily from the same boat, sitting on the pallet at Hamilton. The oldest AGM was four years old and the youngest was just shy of three. That only tells me that proper care and feeding of batteries is important for all types and that AGM's are susceptible to improper care just as wet cells are..

If I was to leave tomorrow, for extended cruising, I would buy AGM's due to the ability to accept a charge faster, which is important when living on the hook. For coastal cruising I will continue with either 6V or 12V wets..

P.S. If you lose a cell in a 6V bank you still have your start/emergency bank to get home on. With either situation, 12V or 6V, you should always replace the entire bank as it's never a good idea to mix a new battery with an old one even if it is the same size and brand. Batteries that will be combined into one bank should be purchased from a high volume distributor and at the same time. Low volume distributors could have one batt that has been there for over a year and the other one came in last week. When buying batteries for boats, especially 6V batteries, it's a good idea to buy them in the late spring after the golf courses & boat yards have begun their replacement regime. This helps to ensure fresh inventory..

 

[Roger Long]

Speaking of proper battery care and feeding:

This is a matter of philosophy and circumstance so I wouldn't fault anyone who does it differently but I run my 2 battery bank as one battery instead of having a start and house battery. The primary determinant of battery life is the depth of the discharge cycles so dividing the larger hotel loads among the two batteries will extend the life of the pricey AGM's.

I do sacrifice redundancy, especially as I have removed the hand start from my engine (actually hand starting it the way it was installed was such a remote possibility that I didn’t even want to be tempted in an emergency). It’s a very easy starting engine, people have even started them with a handful of flashlight batteries collected from all the flashlights on board. Before my next long cruise, I plan to buy one of those portable emergency car start batteries to keep on board.

My hotel loads are pretty modest, no refrigeration or other loads that could be forgotten and run the batteries down. I have LED anchor and nav lights and am gradually converting the interior lighting to LED. I’m mindful of the electric usage and have never come close to drawing a battery down.

An electrical fault could kill both batteries. Currently, the drill for that is to sail to a harbor, anchor, and bring to cheap car batteries back in the dinghy.

Other than keeping them charged up. There isn’t any care and feeding that you can really give AGM’s. I have an on-board 3-stage charger for when I’m on shore power. I’ve returned from overnight-in-the-harbor cruises when the lights were on all evening, plugged the charger in, and seen it go to third (maintenance) stage in less than a minute. That little bit of engine running, even with just a 35 amp alternator, was all it took to recover from a night of typical usage.

 

[John Nantz]

How Long do Golf Carts last?

Let's see, I'm on my second set of four right now. The first set I installed in 1994 and this set in 2001. Not because I had to, it was because we were going on a trip to Alaska for several months. It is now the end of 2008 and the second set is still working good.

Do the math: that's 14 years for two sets with and average of 7 years per set and counting.

Cost: buy them in a set of 4 and from some places you get a better price.

Weight: It's a lot easier to move one golf cart than a single 12v of the same AH capacity.

Maintenance: keep the tops clean with a light solution of baking soda and water.

I attribute part of the lifespan to charging. They like a good brisk charge to keep the plates from getting sulfated. My Heart Freedom 10 charges at 50 amps and the Balmar alternator runs in the 70 to 100 amp range (it's rated at 70 hot but will do more for a bit when it's cold).

Use 2/0 cables and heavy cables to the alternator and grounds.

If you ever get the spreaders in the water you've got other problems.

Bottom line: they work for me.

 

[Bob S]

Thanks everyone. What I have learned is the biggest problem we all face are space limitations. Without a major modification to the starboard settee I can only fit 2 batteries. I have all winter to figure it out. I need to do something because the current set up doesn't work for us. Last year I found myself launching late June because I got caught up in projects. I don't want this to happen again if you know what I mean. I like the 6v's too. Stu's link was very helpful, pros and cons to each group.

 

[jfssail]

Go with the US Battery 2200 batteries. I just finished my fifth sailing season with four of the same batteries. I rarely take them under 40% charge, cruise for 5-8 weeks in the North Channel each summer, and the batteries are still like new. Equalize them once a season and keep them on the charger while at the dock. Expect to obtain another 3 years with them. Maybe the price for lead will drop by then. What are these batteries going for these days? I paid $250 for 4, five years back.
Boat has been on the hard since October and checked on the batteries yesterday, both at 12.6, 12.5 volts after sitting for one month.

Jack F Stewart
1993 C36 #1233 "Windancer"
Port Clinton, OH

 

[Bob S]

There running $96.00 each. I will get them from an industrial battery supplier. They supply batteries for electric fork truck, pallet jacks, etc and have a good turnover of inventory. I've used them for my electric scissors jack and have had good luck. I will follow Maine Sail's advise and buy mid spring to late spring after his inventories begin to move again.

 

[Fairwind]

Few 12V batteries are true "deep cycle construction" The 6v "Golf Cart" batteries are indeed deep cycle and give you the most battery for your money. If you lose a cell with a 12V, you must dispose of 5 good cells and buy 6 more cells. With a 6V (which fail less often) you only have to replace 3 cells not 6...The fewer cells you have in a system, the better off you are..

6V golf cart size AGM batteries are available and do indeed offer advantages in marine applications but the cost/benefit equation can be difficult.

www.fullriverdcbattery.com might offer some insights..

 

[sailingdog]

The converse to this is that if you only have TWO SIX VOLT batteries and one loses a cell, you've got NO HOUSE BANK at all. I'm a big fan of SIX VOLT golf cart batteries, but only in setups that have FOUR BATTERIES minimum.

Few 12V batteries are true "deep cycle construction" The 6v "Golf Cart" batteries are indeed deep cycle and give you the most battery for your money. If you lose a cell with a 12V, you must dispose of 5 good cells and buy 6 more cells. With a 6V (which fail less often) you only have to replace 3 cells not 6...The fewer cells you have in a system, the better off you are..

6V golf cart size AGM batteries are available and do indeed offer advantages in marine applications but the cost/benefit equation can be difficult.

www.fullriverdcbattery.com might offer some insights..