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#11
posted to rec.boats.cruising
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Batteries - what's best and cheapest for long term cruising thesedays
Roger Long wrote:
If you want to charge your batteries faster and harder than they should be charged, are willing to put up with crawling around on top of them sucking acid out of them with a hydrometer and putting distilled water back in to them to repair the damage you have done to them, and are willing to accept the small but quite real danger of having carrying free acid around in your boat, wet cells will give you more bang for the buck and faster charging. If you can live with charging at reasonable charging rates, you'll have a safer boat and get better performance with AGM's. Remember, the outfit that made such a strong recommendation to me about AGM's builds many unattended mission critical systems. That's a good description of how I would like my battery bank to be. There are a lot of mechanical things I like fiddling with on a boat but batteries are not one of them. You are not correctly stating the case by using the phrases 'faster and harder than they should be charged' and 'reasonable charging rates'. But it all depends on your use. If you use a main engine or a generator to charge then I think AGM or gel are out of the question. Unattended operation may require specific requirements. But these are not requirements for boat use. As you say, there are many mechanical (and other) things on a boat to fiddle with, and I don't understand the logic that batteries should not be one of them. You mention using a hydrometer, the only way to find the real state of charge for a lead-acid battery. What is the alternative procedure for AGM? There is none: there simply is no way to find the real state of charge of an AGM! I would say that simply rules them out for anything mission-cricial. Yes it may not be fun but batteries SHOULD be one of the things to 'fiddle' with, IMHO. If you read the article then you will also have read that if you are willing to use 'reasonable charging rates' (=slow charging), standard lead-acid is 'maintenance free' just like AGM and gel. But AGM and gel are much more expensive. You definitely seem to be wrong when you say that AGM will give you better performance - even when using 'reasonable' charging rates. From what I read they will NEVER do that and will most likely fare a lot worse than standard lead-acid, for ANY application. So to quote the article, AGM is good if you want to put your boat upside down for an hour or two. In all other cases, use standard lead-acid. |
#12
posted to rec.boats.cruising
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Batteries - what's best and cheapest for long term cruising these days
On Sun, 15 Jun 2008 11:22:35 -0400, "Roger Long"
wrote: If you can live with charging at reasonable charging rates, you'll have a safer boat and get better performance with AGM's. What do you consider reasonable. One guy says 15% of capacity per hour. If you run them for three hours that leaves time to charge them at the twenty hour rate. One inland lake cocktail cruise per day. Two of the biggest trolling motors made draw how much juice? Casady |
#13
posted to rec.boats.cruising
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Batteries - what's best and cheapest for long term cruising thesedays
On Jun 15, 9:46 am, Salomon Fringe wrote:
...If you use a main engine or a generator to charge then I think AGM or gel are out of the question. And you believe this because...? I and many others have gotten many years of outstanding service from AGMs used in exactly this way. I've got nothing against regular old flooded batteries. They're certainly the best in terms of capacity per monetary unit or capacity per weight for lead acid. But the article you're quoting is being wildly, even absurdly unfair in its comparison of the types of lead acid batteries. He gives AGMs a particularly bad rap by asserting that they are essentially the same thing as a "maintenance free" starting battery. His argument seems to be "well, they've got thin plates and you can't add water to them so they must outgas like mad if you charge them fast and the plates must fail quickly because they are thin." Of course, if that were true AGMs would die quickly in normal use. Yet, I and many other folks, have AGMs that have lasted for 8+ years despite being deep cycled and charged at significantly faster rates than flooded cells. How can that be? The answer is that the author of your article either doesn't know the differences between an AGM and a cheap maintence free starting battery or is being intentionally misleading. As far as I know all AGMs are "valve regulated". Certainly all the major players are. Under normal charging they recombine virtually all gas. While massive overcharging will cause them to vent, modest amounts of over voltage will not hurt them noticeably. Indeed, all of the manufactures that I've looked at recommend periodically equalizing them. Generally you can put all the amps you've go into them as long as you regulate the voltage (max between 14.0 and 14.6 depending on the temperature and the particular battery). Even so regulated their acceptance rates are higher than deep cycle flooded batteries and charge times are quicker. AGMs do have thin plates. But, those plates are packed tightly into the glass mat and physically very well supported. So, they are less prone to physical failure than the thin plates in flooded starting batteries that need to be largely self-supporting. And, at the same time, they have more surface area than flooded deep cell batteries. The net result is that AGMs have very low internal resistance compared to other deep cycle batteries and are more durable. Low resistance also reduces gassing. .... If you read the article then you will also have read that if you are willing to use 'reasonable charging rates' (=slow charging), standard lead-acid is 'maintenance free' just like AGM and gel. But AGM and gel are much more expensive. I've read the article. It is total BS. AGMs are not gels or cheap sealed starting batteries. All his conclusions follow from a false assumption and no evidence for the conclusions is provided. -- Tom. |
#14
posted to rec.boats.cruising
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Batteries - what's best and cheapest for long term cruising thesedays
Richard Casady wrote:
On Sun, 15 Jun 2008 11:22:35 -0400, "Roger Long" wrote: If you can live with charging at reasonable charging rates, you'll have a safer boat and get better performance with AGM's. What do you consider reasonable. One guy says 15% of capacity per hour. If you run them for three hours that leaves time to charge them at the twenty hour rate. One inland lake cocktail cruise per day. Two of the biggest trolling motors made draw how much juice? Casady There's really A LOT to say about batteries and charging, especially because everybody has a different charging and usage situation. One excellent document that has just about all info is this one: http://www.victronenergy.com/upload/...yUnlimited.pdf |
#15
posted to rec.boats.cruising
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Batteries - what's best and cheapest for long term cruising thesedays
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#16
posted to rec.boats.cruising
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Batteries - what's best and cheapest for long term cruising thesedays
On Jun 15, 12:32 pm, Salomon Fringe wrote:
.... That's interesting. Do you have the actual manufacturers discharge graphs that the author says they -for some reason- don't seem to supply? Just go look them up. There's no secret. I don't know why the author seems to think there is. Indeed, the article you posted in reply to Roger down the thread has some good info on this. Did you read it? In any case, the author of your first link doesn't provide a single test or citation to support his views, so why should we believe him? ... If the AGM manufacturers have nothing to hide then that info will be advertised on their websites. It is. --Tom. |
#17
posted to rec.boats.cruising
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Batteries - what's best and cheapest for long term cruising thesedays
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#18
posted to rec.boats.cruising
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Batteries - what's best and cheapest for long term cruising thesedays
On Jun 15, 1:23 pm, Salomon Fringe wrote:
.... Yes I actually have the printed version of that doc, but I don't think there is even a hint of being able to use a AGM for 8+ years while deep-cycling... ? Well, I don't think I said that. What I was trying to say is that the author doesn't seem to have had any trouble coming up with published data. For instance he notes that deep cycle flooded cells ("semi- traction") get 350 cycles at 60% DOD (which is deep cycling) while AGMs get 650-800 depending on construction and chemistry. Service life depends on how you use them but the AGMs look much better than the semi-traction batteries for deep cycle use. His service life numbers suggest that some AGMs will be expected to last 10 years. AGMs have only been popular in marine use for less than a decade so it may be hard to get real numbers. My experience has been fantastic. YMMV... I think some of the very negative responses in the "Dutch magazine" (if they exist, got a citation?) might have been for gel cels. AGMs are not gel cells and linking them is bogus (or maybe even dishonest). AGMs have really good cycling numbers and they are published and you've even posted a link to them. So the Sterling guy's conclusion that you should avoid AGMs because they have "poor cycling numbers" is hard to figure. The rest of his arguments seem to be based on straw men and thin air, too. Who is this guy? Although it's a little off topic http://www.proboat-digital.com/proboat/20080203/ is interesting and has some insight into usage issues. .... Err, I was hoping you would have the links handy... ;-) I was hoping you'd do your own. If you can't google I'll do it for you, but last time I looked both Full River and Lifeline (Concord) had graphs and spec sheets on-line for their AGMs. You may have to plot data from your favorite flooded deep cycle battery for comparison but if the flooded guys have nothing to hide their data will be on-line, too... ;-) I'm not trying to sell AGMs. There are good reasons that they don't use them in golf carts, for instance. But the guy at Sterling seems to have decided that he hates AGMs and then gone off to figure out why. --Tom. |
#19
posted to rec.boats.cruising
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Batteries - what's best and cheapest for long term cruising these days
On Sun, 15 Jun 2008 15:20:55 -0700 (PDT), "
wrote: His service life numbers suggest that some AGMs will be expected to last 10 years. AGMs have only been popular in marine use for less than a decade so it may be hard to get real numbers. My experience has been fantastic. I have heard the same from others whom I respect. I will probably convert one of my house banks to AGMs in the future. |
#20
posted to rec.boats.cruising
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Batteries - what's best and cheapest for long term cruising these days
"Wayne.B" wrote in message ... On Sun, 15 Jun 2008 15:20:55 -0700 (PDT), " wrote: His service life numbers suggest that some AGMs will be expected to last 10 years. AGMs have only been popular in marine use for less than a decade so it may be hard to get real numbers. My experience has been fantastic. I have heard the same from others whom I respect. I will probably convert one of my house banks to AGMs in the future. While I cannot comment on AGM batteries, my experience with gel batteries may be of interest. In 2005 I imported a boat from Florida to Norway. The survey was carried out in mid March and the batteries were Ok and powered up all auxiliaries properly. Three months later she arrived in Norway and the batteries were flat because, as recommended by the makers, the refrigerator was connected directly to the batteries rather than going through the panel and nobody had thought to disconnect it. I tried to charge the batteries with a powerful charger and it could get no current at all to pass through the batteries-they blocked the current completely.. I found that very surprising although I had half expected them to accept, but not retain, a charge. |
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