old alternator vs new gel batteries?

Ed Schenck · Feb 3, 2009

Seems that you are right on with your analysis Dean. My gels gave me no problems for eight years with a similar setup. I attribute that to 1) the batteries seldom being discharged below 70%, 2) the Link 2000 being set for Gels which protects them only from shorepower as you point out, and 3) hardly ever running the engine hard enough to actually generate 14.5 volts.

Despite all of that I switched to AGMs for my cruise and changed out the alternator for a Balmar with 3-stage external regulator. The AGMs are much less susceptible to "frying".

Stu Jackson · Feb 3, 2009

If you have a boat that big and fancy

You really ought to learn more about electrical systems than this Q&A can provide. Many of us have shared electrical system knowledge over the years, but you're asking such a generic basic question that you really ought to buy a book, like Calder's Boatowner's Manual for Mechanical and Electrical Systems.

1. Will the alternator fry the gel house batts? How would it normally get there? I ignorantly supposed the alternator was distributed through the charger/inverter. What happens when the engine is running dockside with shore power hooked up? (the charger is auto-on with power applied).

Yes, if the output is 14.5. You answered your own question. Why would you ever want to do that? The alternator charges when the engine is running, the charger when plugged in. The higher voltage will control. The 14.5 is when you're running at cruising rpms. Idling the engine will give you lower voltage.

2. Is there such a thing as an alternator that can be set to a given voltage? Or must I put it through a regulator? The three-stage regulator seems to be the ticket for gel batts.

The alternator output is determined by the regulator. Period. Again, you've answered your own question. A three stage regulator is a must for any batteries. Mainse Sail disagrees, with reason, but you need to read his material as to why he feels internal regulation works. It will ONLY if you don't over voltage your bank.

An alternative is to buy golf cart batteries in lieu of the gels. Gels are starting to go the way of the do-do bird anyway, being replaced by AGMs. That's because of the limited charging voltage of the gels.

Do some more research on your topic. You could do some searches here on alternators, regulators and charging by Mainse Sail, Bill Roosa and me for more information. Also check out BoatUS.com and Google the subject if you don't want to buy the book, but it'll be the best $50 you can spend on your mega yacht that I can recommend.

Don S/V ILLusion · Feb 3, 2009

Dean
Although you may not be looking for this type response, my reaction is to wonder what it is you are really trying to accomplish. As you said, you are never away from shore power overnight which begs the question why you are going to gels - they certainly have their advantages of a slightly higher charge acceptance rate and ability to hold a charge but neither sounds advantageous in your situation as I understand it.

Perhaps more responsive to your post, all alternators have a regulator - the one you presently have would not be easily modified to reduce the voltage to 14.1 V.

On another issue I infer from your post, leaving lead acid batteries on float charge 24/7 will reduce the useful life of the batteries by as much as 35 to 40% (according to many battery mfgs) compared to cycle charging, which by definition is to charge them only when the need recharging, then leave them alone. The continuous float charge results in accelerated positive grid corrosion, which has the effect of turning the positive plates in the battery into mush: a soft, expanded material that produces increased internal resistance and decreased deep cycle capacity. If this is your current sceanrio and you are going to invest in new batteries, you might want to consider this.

shorty · Feb 3, 2009

AGM's

I've had two Lifeline AGM's for three seasons with that exact same alternator and they're doing great (always knock on wood) . I have a 20w solar panel for trickle charge. Folks at Lifeline support seem to think its a good setup.

Stu Jackson · Feb 3, 2009

Add Don to my list of great respondents

Charge your wet cells up, and leave them off the 24/7 which will eventually kill them. Do some more homework.

Tom Metzger · Feb 4, 2009

Don S/V ILLusion said:
On another issue I infer from your post, leaving lead acid batteries on float charge 24/7 will reduce the useful life of the batteries by as much as 35 to 40% (according to many battery mfgs) compared to cycle charging, which by definition is to charge them only when the need recharging, then leave them alone. The continuous float charge results in accelerated positive grid corrosion, which has the effect of turning the positive plates in the battery into mush: a soft, expanded material that produces increased internal resistance and decreased deep cycle capacity. If this is your current sceanrio and you are going to invest in new batteries, you might want to consider this.

Don - Where did this bit of info come from? To which manufacturers are you referring?

I spent many years running big banks on float chargers with a life expectancy of ten to twenty years. For better cells we expected double that. I don't expect that kind of life from the marine batteries, but obviously the plates did not turn to mush.

Trojan says:
"Trojan recommends using a 3-stage charger. Also called "automatic", "smart" or "IEI" chargers, these chargers prolong battery life with their well programmed charging profile. These chargers usually have three distinct charging stages: bulk, acceptance, and float."

I really love the internet.

Bill Roosa · Feb 5, 2009

trickle charge

Don is referring to chargers that stay on trickle charge (more than 0 amps) all the time once the batteries are fully charged. A good marine charger is going to sense the battery voltage and then cycle on and off trickle as needed. If it has a 3 stage it is almost assured to have the cycle feature. To check just note the voltage after the batteries have been charged for several days. It will cycle on and off (higher and lower voltages) at a very long period. The on period will be relatively short followed by a short period of rapid voltage drop as the battery "rests" then a long period of slowly dropping voltage till the charger reaches it set point. It will then repeat. This is highly dependant on the health of your batteries. Very healthy batteries having longer (days between cycles) periods.

Tom Metzger · Feb 5, 2009

These are only the "latest" chargers that sample voltage and there is not enough history to determine if they are any, or significantly, better than the pure float chargers. True, some pop up based on time, I think mine does after 21 days of no real load, but I doubt if this has any effect unless the time goes out for a year or so with a 6 cell battery.

I used to get cell readings every quarter with 60 cell strings, but they are much more sensitive to problems such as voltage reversal. Cell reversal is pretty much unheard of at 12 volts because the other cell voltages would have to get up to an average 2.7 Volts which is pretty much undo-able. We would generally equalize every year or so, as required.

I know the manufacturers love to sell new products, but that doesn't make them better. Take combiners, as an example. Lots of us consider them just that much more hair in the scuppers. Now there is a whole new thread or two.

Stu Jackson · Feb 5, 2009

You may be interested in this charger evaluation

http://c34.org/bbs/index.php/topic,4352.0.html

Tom Metzger · Feb 5, 2009

Stu Jackson said:
This is what having your battery “all sulfated up” means. Most flooded cells need to be completely recharged every 30 to 45 days to avoid permanent sulfation.quote]

Where I live in the east people pull their boats out of the water in the fall and leave them until the spring with no attention and no battery charging. I can assure you that we do not have to replace batteries on an annual basis. A lot of that time the temperature is not what would be described as cold.

Standby batteries do this as a matter of course, summer and winter.

The standard for new batteries is that they not remain on the shelf for more than six month without being charged. At six months they must still meet the acceptance test as a new battery.

Stu Jackson · Feb 6, 2009

Tom, that would be

under use. Sure, people leave their banks fully charged which is the concept: fully charge and let sit, don't always float. Doesn't matter if it's winbtertime or in season or somewhere where it doesn't require getting boats out of the water.

Tom Metzger · Feb 7, 2009

Stu - Are you suggesting that it is better to let a battery sit than to float it? Where is the logic in this?

In old cool hydro stations we had batteries on float for years at a time heading for a forty year life. If we did what you are suggesting the first time an outage came along we couldn't restore power because the batteries would be down. The idea was to have them fully charged when you need them, and you didn't get advance notice when an outage was going to happen.

old alternator vs new gel batteries?

deneaux

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Ed Schenck

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Stu Jackson

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Don S/V ILLusion

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shorty

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Stu Jackson

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deneaux

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Tom Metzger

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Bill Roosa

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Tom Metzger

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Stu Jackson

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Tom Metzger

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Stu Jackson

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Tom Metzger

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