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Old 04-01-2010, 11:48   #46
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AGMs are in certain respects 'better' than flooded--especially if you fly an airplane upside down. But we like to keep our boat right-side up, so this particular features doesn't do much for us.

Although they are WAY more expensive, AGMs do not last any longer than flooded batteries--a chart I saw recently indicated that AGMs & flooded batteries have the same service life.

A friend of ours bought a brand-spanking new Nordhavn just after we bought our Trojan batteries; he had to replace them (not the Nordavn) in November. Our batteries are fine. No doubt his electrical system is far more tricked out than our own, but that apparently didn't amount to much.

Unlike AGMs, flooded batteries need to be watered and they need to be equalized every few months. No big deal.

The fact that they give off a little gas when charging is irrelevant--the stuff is lighter than air and if you're boiling the hell out of them you've got other problems (problems, by the way, which would kill your AGMs but which your flooded batteries might very well survive).

As he bought his new AGMs, the same friend noted above resorted to that tired cliche: "Owning a boat is like ripping up $100 bills in the shower-just quicker." He's wrong, though. The problem isn't boats; it is the urge to have to the best even though the conventional is good enough or, in many respects, better.

I wonder how many cruisers who use AGM batteries also use gold-plated audio cable for their sound systems. Admittedly, we still use plain copper--not even tinned (God forbid)!!
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Old 04-01-2010, 13:40   #47
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I currently have 1 starter battery and 2 -12 v house batteries separated by a combiner all in good shape. I'd like to add 2 - 6 volt batteries to the house. Is there a way to tie the house batteries together to keep them from discharging from each other? the 2 house batteries are good and I don't want to just throw them away and buy 4 - 6v batteries now. My plan is to eventually have 4 - 6 v house batteries. My alternator charges the house batteries first then connects to the combiner then to the starter batt. Starter battery is connected straight to the starter.
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Old 04-01-2010, 15:13   #48
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It is not a good idea to combine different types of batteries or to combine new batteries with old batteries. If you add the two 6 volt batteries to your housebank (which doesn't seem like a good idea), when you add the next two 6 volt batteries, you'll be combining old batteries with new, which isn't a good idea either.

Why not wait until you're done with the 12 volt batteries and start off with a fresh set of batteries?
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Old 04-01-2010, 16:01   #49
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Quote:
Originally Posted by gettinthere View Post
My reading over the years has always shown wet cells last longer than agm's. Almost twice as long. I've never, before this thread, read of agms lasting 10 years.
The trick to making AGM's last for a long time is to never over-discharge them and never over-charge them. Their charge and discharge cycles must be carefully controlled.

Since the AGM's are sealed, you can't add water if you overcharge them. They vent, and that's it. they're done.

If you over-discharge them, they shed active material from their matrices and they're done. The spiral-wound matrix is a little more fragile than a conventional plate, wet-cell battery.

As for checking the electrolyte in wet-cell batteries, if you buy a modern, Schumaker battery charger or battery tender, they will shut off when the battery is fully charged, or go into "standby", preventing an over-charge that boils off the electrolyte. This greatly reduces the need to check the levels, and almost entirely eliminates the need to add water because it hardly ever boils away.

You AGM lovers make it sound like it has to be checked every other day or something. In a sailboat application, the only advantage to an AGM battery is no mess in a casualty like extreme heeling or capsizing.

AGM's have other excellent properties like being able to discharge high amounts of current very quickly, which is great for racing electric vehicles, or heavy starting applications, but that doesn't often apply to sailboats.
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Old 04-01-2010, 18:26   #50
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Thanks, Momo.

will do just that.
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Old 05-01-2010, 08:16   #51
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I have found that combining a large solar array, with an MPPT controller, combined with wet cells, is a great combination. Most of your charging is at a lower rate, so acceptance is irrelevant. The MPPT controller gets the cells charged up to their maximum without any fear of over charging. MPPT controllers pulse the power to the cells, and it seems that they gas less because of it, so watering is done less often (and less gassing).

We have a 240 watt array, and two 1275 wet cells as the house bank, for 300ah. When on the hard, if needed, we have a Iota 45amp charger, which also pulses the batteries. So far, so good, and not overly expensive either.


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Old 25-01-2010, 15:51   #52
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Trojan T-105

Southwest Florida

Just bought (4) T-105s for $86 ea. plus $1.50 environmental fee & $16 core. I compared to the Costco GC batteries which are $76 ea. I figured the $10 was worth it going with Trojan, the good comments here and the fact the Golf Cart dealer I purchased from understood my concerns about freshness, shelf life, etc. The batteries I bought were manufactured Jan 10 and stamped Feb 10! (I'm using them before their birth!)

Replaced (2) 8D flooded (I'm glad those things are gone!)

I was concerned about starting an engine with the Trojans. Trojan put my fears to rest, and they are right! Starting the engine is no problem! From Trojan's FAQ:

"Deep cycle batteries can be used for engine starting but starting batteries should not be used for deep cycle applications. A deep cycle battery may have less cranking amps per pound than a starting battery, but in most cases a deep cycle battery is still more than adequate for the purpose of starting an engine."
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Old 27-01-2010, 00:28   #53
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We have one battery bank -- eight six volt Trojans. Six years old now. No fancy electronic do-this and do-thats on the charging system. No problems with venting; check the fluid levels every eight weeks or so; add water less often. No hydrometer (I can tell if there's a problem without one). Never spilled any acid 'cause we don't sail upside down. Only time we couldn't start the motor was when the starter broke, which had nothing to do with the batteries. As long as simple + cheap = seaworthy, we're happy. All too often the equation runs: complicated + expensive = frigging nightmare.
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