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Discussion Starter #1
Went to visit the boat last weekend and found that the house bank (3 3-year-old group 27s) was at 11.4v. The starting battery is at 12.4v. This degree of difference doesn't sound right to me. The only thing connected to the house bank is the HeartLink monitor. I did listen to a bit of radio the last time I was aboard winterizing, but that shouldnt draw much from as large a bank as that, should it?

In prior years, I would visit once/month and connect a 100' extension cord to my onboard charger. When I would visit next, I'd find it unplugged, but clearly only after the bank had come up to charge. This year, I'm more than twice as far from power. I'd have to use at least two cords, and I'm fairly certain one would "walk" if left unattended (the one not attached to the boat). At what point of discharge do I have to start to worry that it might freeze, thus prompt a recharge visit?

TIA
 

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Joel,

Freezing is just one of the things to worry about. I'd be more worried about long-term damage to the batteries.

Any lead acid battery left in a less-than-fully-charged state will deteriorate through sulfation (formation of PbSO4 crystals on the plates) and stratification of the electrolyte, inter alia. This includes brand new batteries on the dealer's shelf.

Exercising and equalization can sometimes help somewhat, but if the lead sulfate crystals are deeply imbedded you may not be able to reverse the damage.

If getting shorepower to the boat is not possible, could you maybe rig a solar panel or two? These could help extend the life of your batteries, though you say they're 3 years old now and with the treatment you describe they probably don't have a lot of capacity left.

If solar panels are impractical, I'd remove the batteries for storage over winter where they can be left on near constant charge with a smart charger. Group 27's aren't all that big -- not like removing 8-D's :)

Bill
 

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Discussion Starter #3
I forgot to mention that these are flooded batteries. Is it the case that sulfation occurs only when the state of charge is below a certain point? At what point does this become a concern? If 12.6v is fully charged, is 12.4v a problem, or is it less than that at which point it becomes critical to charge? Does temperature affect the rate of sulfation? I guess I can hope that it is slower at lower temperatures.

In previous years, I don't believe that the state of charge ever got very low, but the combination of the distance to power and the distance from home to the yard are making this more of a challenge this year.
 

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A few questions for you. Do you turn the battery switch off when you leave the boat? There has to be a draw on the low battery somewhere. First year I owned my boat I left the battery switch on because I had a solar panel hooked to one battery and was using the switch to charge both batteries. Every time I would go to the boat the batteries voltage would be down more. I stared cussing the solar panel. I found 2 draws 1) memory on the radio and 2) the little LED lights on my breaker panel. Once I disconnected the breaker panel no more draw and the batteries came right back up. The solar panel was a little maintenance one, by the way.
 

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Discussion Starter #5
Thanks. One of the reasons for my OP was my concern over the two differing states of charge between the two banks.

I leave the main switch (Blue Seas Dual Circuit) set to "OFF". I have a few items wired to the hot side (house bank) of the main switch, though. One is the bilge pump. Since I have a garboard drain plug (removed for winter storage), the pump is set to "Manual". Two is the stereo memory. I have a switch in that line which I switch off for the winter. The third is the HeartLink 10 battery monitor, which is not switched. The HeartLink is the only known draw. There are no connections to the hot side of the main switch for starter bank.

Based on btrayfors posts above, I've started to think about a small (20w) panel for the house bank and maybe a 10w for the starter. One of the sites I looked at said that one needs a charge controller to prevent overcharging "if the solar panel to battery ratio is greater than .10 W / Ah". My house bank is about 225 AH, so I shouldn't need the controller for a 20w panel. The starter battery might be closer to a problem with a 10w panel, though. I would plan to hard wire the charger to the battery banks for the winter.

What do you mean by, "The solar panel was a little maintenance one, by the way"? Is there a high maintenance kind I should be aware of?

TIA
 

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How is the water level in the batteries?? If you haven't checked it recently, you probably should.

If the water level is low, the batteries could be low due to the electrolyte levels not covering the plates fully... in which case, the batteries are likely toast.

I just added a 25 watt solar panel to the boat to keep the batteries topped off on my boat today. :) It goes through a charge controller and should be able to keep up with the parasitic loads as well as the self-discharge rate of the wet cells.
 

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Wet cell batteries can self discharge faster than a small panel can put back depending on the size of the bank (it's a percentage thing).
 

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Yup... true that... but in near freezing weather, the self-discharge rate of wet cells drops a good bit... :) and I've done a rough estimate of the parasitic loads and self-discharge, and the 25 watt panel should be more than sufficient. Especially since it is going through an MPPT type charge controller. :)
Wet cell batteries can self discharge faster than a small panel can put back depending on the size of the bank (it's a percentage thing).
 

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Discussion Starter #10
I did a search on battery discharge rates and got a brain ache!

I'll check water level this weekend. If it is low, do I assume they are dead, or is there a test? Do I refill and then use a hydrometer to test the state of the electrolyte? Or will that tell me nothing about sulfation or whatever the amage is called that occurs when the electrolyte level is left to get too low?

Should I just trash them all and get new AGM batteries? Or golf cart batteries?
 

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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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Discussion Starter #12
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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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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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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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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Discussion Starter #20
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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