what size batteries to buy ?

[Jrpla]

This is what I have

I have a Beneteau 32 with a Yanmar 2GM13.Equipment I use are:Regular navigation electronics (GPS, radio, autopilot)Norcold Ice Box conversion unit ($600 at defender, 3.3amp/hour when running)Lights, water pump.I have a Xantrex 20+ for shore power charging but this one you will not needed if you are planning to go live away from the dock.I installed a new marine 80 amp alternator on my Yanmar that cost me $90 on ebay. This will charge batteries when running, if needed. I installed a 64 Watt Unisolar NO-GLASS Marine Solar Panel Kit that i found on ebay for $350, this give me 3.5amp an hour.Go to Solar Stick school, here you will learn what system you will need: http://www.solarstik.com/html/school.php , The solar stick is great but too expensive.My batteries, all wet, maintenance free, with a port to add water if needed.1. 1 Group 27 for the motor (use only for emergency)2. 2 Group 31 as house batteries in parallel. (Truck batteries)Golf car batteries are good too buy too much maintenance and too much weight. All my batteries are not marine, and cost me $60 each. I went to a place that sells batteries for trucks and construction equipment. Marine are too expensive and are the same.

 

[Maine Sail]

Not really true...

My batteries, all wet, maintenance free, with a port to add water if needed. Golf car batteries are good too buy too much maintenance and too much weight. All my batteries are not marine, and cost me $60 each. I went to a place that sells batteries for trucks and construction equipment. Marine are too expensive and are the same."

Cutting corners on your electrical system, is not always a cost saver. The above statement is just NOT true. Even among group 31 batteries there is most definitely a difference between a group 31 starting battery and a group 31 deep cycle just look at the weight and the plate thickness. As for maintenance free wet batteries on a sail boat, it's not a good idea if you expect more than a year or two out of your batteries.

In reality any battery used for anything other than starting, that requires it to be discharged and charged regularly to 50% SOC, you really want a deep cycle or industrial deep cycle. The above author also stated that 6V are more maintenance and this also is just not true. Even a "maintenance free" car battery, when used in a boat, will require topping up with water or they can be killed. It takes me less than three minutes to top my golf cart batteries up with water and they rarely need ot more than once per year. 

The information below may help to clarify. I'm guessing by "marine" in the above author's post is referencing companies like West Marine. Personally I never buy batteries at West Marine because they are always over priced. I used to use Trojan T105's which are true 6V deep cycle batteries and great ones but their price has skyrocked out of control.

To answer the above posters question regarding weight, with real data and not just an off the cuff statement of fact, a Trojan T105 6V golf cart battery weighs 62 pounds and a true deep cycle group 31 weighs 59 pounds. Now granted you NEED two T105's to make 12 volts but you also need two group 31's to get even close to 200 amp hours. I don't know many sailors running one 12v battery for a house bank. If you are really worried about the 3 pound difference then your could leave three beers at home. The T105 or any 6V golf cart battery will almost always out perform and out last any group 31 deep cycle even one made by Trojan. Sometimes group 31's are necessary though like when you only have room for three house bank batteries not four and need the most ah's that will fit.

The cost equation is simple too. My last T105's I purchased cost me 64.25 each making 225 amp hours for 128.50 or 1.75 amp hours per dollar spent. Sadly those same batteries today are well over $150.00 each here in Maine. Even if the above posters batteries are putting out 95 ah for his 60.00 he is only getting 190 amp hours for $120.00 which equals 1.58 amp hours per dollar spent. Using a calculation like this is the only true way to determine battery cost.

I'm not even going to bother calculating the fact that at best his group 31's would almost certainly last less life cycles than T105's can. My brothers bank of four Sam's Club golf cart batteries (read $46.00 each) are now six years old and still going strong. 

These are some general (minimum - maximum) typical expectations for batteries if used in deep cycle service:

Starting: 3-12 months (which is what a group 31 "maintenance free" battery is)

Marine: 1-6 years

Golf cart: 3-6 years

AGM deep cycle (CLAIMED): 4-7 years

Gelled deep cycle: 2-5 years

Deep cycle (L-16 type etc): 4-8 yearsRolls-Surrette premium deep cycle: 7-15 years

Industrial deep cycle (Crown and Rolls 4KS series): 10-20+ years

 

[RG]

Battery life

I am not as experienced as most.....okay everyone els, when it comes to batteries, but I did learn a thing or two while in the military that keeps batteries alive longer.keep batteries clean. Grit and grime on top can cause a battery to drain due to the two posts having a connection thru the grit and grime. keep battery fluids topped off. This can kill a battery.Keep the posts and connectors clean. Occassionally take a wire brush to clean the connections. Use will cause a slight corrossion and this can hinder performance and charging.heat is one of a battery's worst enemies.The taller the battery the longer life it will have, as long as it is maintained propery. As a battery is used, it sluffs of particles from the plates. These particles fall to the bottom of the battery case. Over time the particles build up and come in contact with the plates in that cell. This causes the cell to short out or become a "dead" cell. The taller batteries have more area for the particlae to collect, thus extending the battery life.

 

[Paul]

Sam's Club 6 volt units

I just went to Sam's and saw the 6 volt battery's by Energizer. $62 each.Any one use the Exide Energizer brand? Not sure if they are the same from the Sam's batteries mentioned taht are many years old.

 

[BobW]

Exide <> Energizer...

so unless Sam's Club is doing some branding on their own, there's some confusion here.Exide makes good batteries... I've set up and sold hundreds of them in large telecom banks. By large I mean 2v cells holding 15 gallons of acid set up in banks of 24 cells. Fun stuff!In real terms, if you buy a $62 battery, you're getting $62 worth of battery....unless you buy it at WM, but that's another issue. ;DThe problem is that you're not going to know whether your battery is going to last for 2, 4 or 6 years until.... well, 2, 4 or 6 years. While the care you put in and the depth of the discharge cycles are important, so too is the quality of the battery itself, most particularly the construction and thickness of the plates.As RG, (who knows more about the care of batteries than he thinks ) points out, each time you use (discharge/charge) a battery, some of the plate material sloughs off. The more plate material (along with adequate settling space at the bottom of the cell), the longer the battery will last, in general terms.So, if all other factors are equal (and again leaving marketers like WM out), higher cost = more plate material = longer life. So you have to make a value decision, based on your expected usage - if you're a weekender, the extra bucks probably won't be worth it, but for a cruiser who is cycling his batteries every day, the cost/value advantage is significant.Finally, lead-acid battery costs seem to have skyrocketed in the past year.... some people are blaming China's steadily increasing consumption of lead (along with just about everything else, including oil, steel, cement, etc.).Cheers,Bobs/v X SAIL R 8

 

[BobW]

Cost of lead has doubled in the last 6 months....

and there isn't much to a battery except lead and some sulphuric acid.In fact, lead has gone from $.20/lb in 2001 to $.88/lb today. I guess we're lucky not to see a corresponding increase in battery prices, but not quite sure why.So when the store gives you a $8 trade-in on your old battery, somebody is getting over - a 60 lb battery has about $50 worth of lead in it, and while it needs to be melted down and cleaned up, it's still useable lead. Even the sulphuric acid is reusable.I guess that's why batteries don't cost too much.Cheers,Bobs/v X SAIL R 8

 

[Ross]

If only it were so easy. A careful check of

battery chemistry will show that there is very little unalloyed lead in a battery. The sulfuric acid is just a hazmat to be disposed of and the case is plastic to be recycyled. There is a quantity of wood in the battery along with sulfur compounds of lead. Should you attempt to salvage the lead from a battey it is unlikely that you will get fifteen pounds of metallic lead alloy but you will get a pile of very nasty skimmings.

 

[BobW]

97% of the lead is recycled...

according to the link below. I also found a listing that indicates that 'drained lead-acid batteries' are worth $.23/lb. That includes the case, separators (which used to be wood, but today are normally PVC) and support structure.The US EPA states:"A typical lead-acid battery contains 60 to 80 percent recycled lead and plastic."The lead is alloyed with antimony, and I'm afraid my chemistry (and/or research skills/time) aren't enough to determine whether the lead must be 'un-alloyed' from the antimony during the recycling process. My guess is that it does, but that the antimony can also be recycled.The positive plate is made of lead dioxide, PbO2, or 'spongy lead', but that shouldn't cause a problem with recycling, should it?As for the sulphuric acid, given the difficulty in disposing any toxic waste these days, I suspect that it is economically viable to recycle it. Here's a link to a detailed description of the process:http://www.greener-industry.org/pages/sulphuric_acid/8SulphuricAcidRecycling.htmObviously, all of this becomes more economically viable as the prices of the raw materials increases, as well as the cost of disposal.From what I have read, lead-acid battery recycling is a pretty successful program.Cheers,Bobs/v X SAIL R 8