Does anyone have experience with the longevity of AGM batteries? the particular ones i have in mind are 250 amp hr (100 hr rating) 12v batteries. My employer uses exclusively L16 style Rolls-Surerette batteries, 480 or 530 amp hr (100 hr rating) 6v and expects 7+ years out of a battery bank. these cost about $350-400 vs $800 for the AGM batteries. so simple math favors the lead acid ($800 for 500 amp hr @ 12v vs $1600 for 500 amp hr @ 12v) but are the manufactures claims of longer life on the AGM backed up? AGM has the advantage of zero maintenance, which is a nice but hardly worth double the price. another consideration is that in 10 years, perhaps lithium ion batteries will be affordable, or another battery with better characteristic will come along. the money saved today by going with the proven lead-acid batteries could be more wisely invested. i'm designing a system for some off-grid folk, very low usage. DC fridge, lights and occasional movie, two independent systems, one 12v for the fridge and pumps, one 24v for inverter. 1200 watts of panels. they are limping along on about 700 amp hrs @ 12v ("golf-cart" 6v) now and we are debating AGM vs. Lead-acid to expand the battery capacity.
tl;dr: Do AGM batteries have double the usable life-span of lead-acid?
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AMG do not have twice the life of lead acid. Their biggest advantage is the no maintanance feature, if your people are not good at taking care of things, if they forget to check the water levels regularly and take care of the lead acid they could have problems as well as a reduced life of the battery. If they will do the required regular checking and maintain the batteries the lead acid will work well and last a long time. I am guessing that you are going with the deep cycle lead acid type 27 that are used in RVs and Boats etc. I have an Electric Car and went with the wet lead acid batteries because of the cost. I looked at the AMG as well as the lithium Ion, I would have loved to go with the Lithium because of the lighter weight, more amps, and longer life, but the cost of 3 times higher was just too much difference for me to handle. You are correct that the Lithium Batteries have come down alot in price and may continue to drop in price as more Companys get into their manufactering. But today they are still pretty pricy. You can argue that the Lithium do last much longer than lead acid and that amp for amp, volt for volt they cost the same in the long run, and have more storage in the short run. Lead Acid is very forgiving, nothing happens if you happen to over charge them. Lithium is not as forgiving and can explode if not charged correctly. The chargers for Lithium are much more complicated and much more expensive. That is about as much as I can tell you, Pays your money, Takes your chances, Choose, they each have advantages, and they each have disadvantages pick what works best in your situation.
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For a home/cabin--the case to do AGM is one of two issues:
1) whether you can vent the cabinet. Some do AGM because they want the batts somewhere hard to vent properly.
and 2) whether they can/will maintain them. The price difference will more than pay for an automatic watering system for the lead acid--especially if they plan to add capacity in the future.
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I have no experience with lead-acid batteries, nor any other kind dealing with photovoltaic or other alternative electrical generation.
However, my research for our near future system has led me (pardon the inadvertent pun) to discount lead-acid batteries entirely.
They are very expensive, and they cannot last more than six years in bad cases, ten in the very best. That means that once a decade you are faced with apending $5~10,000 for replacements, and have tons of lead to deal with along with the dangerous acid. No thanks, I'll go another route.
I have recently discovered Thomas Edison's nickel-iron battery. It's not a direct, one-to-one drop in replacement for the lead-acid battery, but it comes very close. (The electronic controls are somewhat different, and the number of cells required is slightly greater.) They are even more expensive, but they last up to a century. Jay Leno and his wife each have a Detroit Electric car from the pre-WWI era, running with the same batteries installed at the factory. Others have batteries that are 50 or 60 years old and still running at the rated capacity.
I'll probably spend 15~20% more for the initial purchase, but that will be my final cost for batteries. They'll outlast me, fer shure, and probably the solar panels on the roof as well as the electronics to keep 'em going.
Neither nickel nor iron is toxic, like lead. The Potassium Hydroxide (KOH) electrolyte is far less dangerous than sulfuric acid (H2SO4). Of course, they produce hydrogen, but because the electrolyte is compatible with platinum, it can be captured and returned to the cells as water by catalytic cell caps, so there is no need to vent them, and they go a very long time without needing additional water. They operate in temperatures from -40~+60°C. They can remain uncharged for decades, even dry out, and there is no necessity for do much more than refill the electrolyte and charge them.
The Edison Battery Company was sold to Exide a few decades back, and they stopped making them. But there are three importers that I have found who can fill your needs. One's a dozen miles from our Colorado home. Another is in Montana, but I have forgotten where the third is located.
was just doing more homework on desulphating lead acids, and they point out that the cause of much failure in LA cells is stratification, that not charging high enough to bubble the acid, and stir it up, causes crystallization in the lower portions of the plates.
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I think this is an important topic, so I'm commenting even though the thread is old. My research suggests that the best choice for off grid alternative energy systems is a relatively small forklift battery - lead acid. The initial cost is less than just about everything else, and they will last 2-3 times as long as most alternatives when properly maintained. I've looked at just about every alternative, and I the forklift battery always stands out.
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