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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #11  
Old 12-29-2008
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Joel,

The questions you pose are all good ones. Unfortunately, there are no easy -- read simplistic -- answers, at least not any correct ones.

Let me address a few of them quickly.

Q: When does sulphation of the plates begin?
A: It begins at relatively high voltage levels, and accelerates as voltage drops. A fully charged battery leaving the factory will begin to sulfate, and as the voltage drops thru self-discharge or other means the sulfation rate will increase. Even a battery left on float at, say 13.2VDC for a flooded battery at room temperature, will begin to sulfate. That's why periodic exercising (deep discharges and full recharges) and equalization (raising the voltage to 15.5V or so for a 12V battery over several hours) usually have beneficial effects in knocking PbSO4 crystals off the plates and in bubbling enough to distribute the electrolyte more evenly and thus reduce the effects of stratification (different levels of acid concentration within the "layers" of the electrolyte, leading to differential corrosion, contamination, etc.).

Q: What can I do to reduce sulfation to a minimum?
A: Keep your batteries fully charged whenever possible, exercise them occasionally, and equalize them every few months.

Q: I let my batteries go dry. Will that kill them?
A: When you let the electrolyte level drop below the top of the plates, you are very likely to incur some damage. How much depends on a number of factors. All you can do is to add enough distilled water to cover the plates, fully charge, exercise, and equalize the batteries. And pray! Most likely, you will have lost some capacity.

Q: Should I replace my batteries if I think they're damaged?
A: Yes, BUT. There's no sense replacing your batteries unless you have examined your system setup and are prepared to treat the new batteries well. This means, at a minimum, that you have a 3-stage or better smart charger, properly sized for your battery bank; that your engine alternator has a smart regulator; that your wiring is of adequate size; that your connections -- all connections -- are clean and tight. If you don't tend to these things you'll be throwing good money after bad.

Q: Should I buy flooded, AGM, or gelled batteries?
A: IMHO, this depends very much on an analysis of the type of use intended, and your ability to care for the batteries regularly. Flooded batteries are still the price point, i.e., they are more economical than VRLA batteries. However, they require attention, they cannot be installed on their side or upside down, etc., etc. AGMs have lots of advantages, but some disadvantages, chief among these is their relatively low cycle life. Gelled batteries have greater cycle life than AGMs, but not as much as flooded batteries, and they are wonderful in applications where the boat sits at the dock with the charger on most of the time, with occasional overnite jaunts. I have some 12-year old gels in my basement which spent 10 years in service on a sailboat with this type of use. They still test about 90% good.

Flooded batteries can last a very long time, especially the pricey but very well built Rolls/Surette models. These can last 10-12 or even 14 years or so in heavy service on a cruising boat.

Q: Should I wait?
A: Maybe. There are several new battery technologies just coming to testing and to market. These hold great promise, if they don't turn out to be priced too high. Of particular interest to me is the Firefly Oasis microcell technology developed by Caterpillar; their Group 31 battery is going into full production next quarter, but initial sales will be to the trucking, military and other targeted sectors (not, unfortunately, the small-by-comparison boating market).

Sorry to have carried on so long, Joel. Hope I answered some of your questions. One strategy might be to commit, in your mind, to getting new batteries in the spring, just leaving the old batteries where they are. Spend the winter reading and learning, and planning your electrical system to support the new batteries in grand style :-)

Happy New Year!

Bill
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  #12  
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Bill,

Thanks for the detailed an thoughtful answer. My questions were being asked, at least partially, out of frustration.

I have a 90A Balmar alternator and a 3 stage Balmar smart regulator feeding my two banks connected by a Blue Seas ACR relay. The wiring was all redone last year to ABYC standards and sized appropriately according to my electrician. When at a dock (exremely infrequently) or on the hard, charging is via a TrueCharge 20+ multi-stage charger. The 3 group 27 house batteries and single group 24 starter battery seem appropriate to the loads we put on them and are going into their fourth year. I think from the equipment and setup perspectives, we are OK. They have been challenged by my "benign neglect" and by the fact that for their first two years, they were fed by a single-stage regulator which, apparently, never brings them get to a fully charged state. Last spring I put almost a half-gallon of distilled water into the 3 house batteries - I'd gone the entire prior season without checking them. I have to hang like a bat under the cockpit to get to them. That probably is the reason they are showing the charge they are. And why a maintenance free battery is so appealing. Since we mostly sail, we don't often motor long enough to get to the float portion of the charge cycle. Maybe AGM batteries with solar trickle charging is the way to go. Perhaps we need more capacity with AGM (than flooded) to support our electronics addiction (reefer, radar, plotter, stereo, etc.) if, as you say, AGM doesn't stand up to cycling as well as the floodeds do.

This is the start of the research. Thanks again.
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Old 12-29-2008
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Battery Drain Mystery

HI Joel - I had the same unattended battery drain problem last year. The problem, I discovered, was caused by the small but 24 hour a day continuous current drain by my Link 20 battery monitor. Now, I disconnect my battery leads at the batteries for winter storage and only see minimal, and expected, voltage loss. Hope this helps.
Steve
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Old 12-29-2008
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I run 3 Optima group 27's AGM types as my house bank with a capacity of 210 ah, have a Xantrex XBM to monitor it and a 80w solar panel fed thru a charge controller (ACR etc to split with starter, with is the same as the house regarding type).

When I'm in the water over the winter I have no power at the pier. I put the boat up in November at 99%, check occasionally during the winter, and come back in april at 99%, with propane detectors, fans, monitors and the occasional winter project that needs music and lights.
For what it's worth, I don't plug into the pier in the summer either, and I've never arrived at the boat (at least weekly, more often several days a week) with the XBM showing less than 99%.

Benign neglect is my middle name. Fortunately my system tolerates my style of battery management. I recommend the same for all my friends. Who wants to break out a meter and a calculator before they turn on the MP3 player?
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Pull the batteries and take them home and hook them up to a battery minder or a good 3 stage charger with an equalization feature.
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Old 12-29-2008
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Joel, wet cells will take permanent damage from irrreversal sulfation after sitting for as little as 30 days without charging. They don't need a lot of power to prevent self-discharging and sulfation, but 11.4 volts is considered a totally dead battery and even deep cycle batteries have a limited number of "total discharges" available before they go belly up for good. I wouldn't replace them yet--I'd see if they take and hold a charge.

If they went flat because there was a drain on them, AGMs will do no better. If they went flat simply from neglect and self-discharge...AGMs can avoid that.

With small solar panels you have to shop carefully, most of them are NOT waterproof, not weatherproof, and will be destroyed by one winter season on deck. You don't need a lot of wattage to keep batteries from self-discharging, but you will need more if there's some type of drain, and you have to bear in mind that in the NYC area your panels will provide their rated output for the equivalent of four hours per day--and only a fraction of that when it is not full sun. They'll also provide zilch if they get covered by snow, so you'll still need to visit them from time to time.

But it is either solar, or take them home, because yard power just isn't reliable, especially in the winter.
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Joel,

Flooded batts should really be removed from the boat during winter storage and put on a maintanence charger. If you want to avoid hanging like a bat in the locker, do consider a valve regulated battery, either AGM or Gel.

My preference is AGM and I have (2) 6V AGM wired in series for 300AH at 12V. I replaced a 4D that had gone bad because it was neglected by a PO by consistent undercharging and water levels not topped off.

You have already invested in the charging techology (3 stage regulation) to support an AGM or Gel type. Why not take better advantage? The AGMs will take all the amps your Balmar and Tru-Charge will put out.

Another advantage as some have pointed out, is that you can simply leave them installed over the winter and expect very little self discharge.

Jason
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Joel...You'v gotten some great advice above. Based on YOUR comments on how you use your batteries and boat, I'd suggest that your house bank is probably close to toast from neglect and improper charging routine.
I further suggest that you stick with reasonably cheap flooded batteries because AGM's NEED to get to 100% charge regularly (like every couple of weeks) and you will be unable to do that...thus you will kill them faster than you would flooded cells and they are 3x more expensive to begin with.

You have a good active charging system when you can run your engine...but putting back in the last 10% of charge can take hours and hours and you won't be able to do that off the engine.
Since you can't charge from the dock very often, I am going to suggest that you bring the dock to the boat...by buying a portable generator Honda2000 or similar and hooking it up to your 3 stage charger for quick and complete charging along with occasional Equalizing.
Seems to me this will let you do the job most economically while also providing versatility for other on board AC needs.
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Honda 2000i at 1000 bucks plus toting gas, 80W panel and charge controller for 800 bucks and never touch it again, you choose.
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Old 12-30-2008
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Well, this year I think I can borrow a generator. How long should I need to let it run to top off the banks? I know this is a hard question - what is the state of discharge, how big is the bank, generator output, etc. I'm just wondering if this is a let it run while I go eat lunch or a let it run overnight kind of thing.

TIA
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