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purple_stars purple_stars is offline
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First recorded activity by BoatBanter: Jul 2006
Posts: 8
Default Interesting Lead Acid Battery facts

Larry wrote:
In our ongoing watered golf cart vs. expensive maintenance-free gauze
battery discussion, there are some very revealing facts the author points
out that I'm sure the battery sales people wouldn't want you to look at
too closely...

[snip]

Good stuff. My own experience with lead-acid batteries leads me to
believe that no matter how well you take care of them they don't last
more than a 2 or 3 years. For example I had a pair of deep cycle
marine batteries in the truck to run ham radio equipment, I installed
those in about November of 2004. They aren't deeply discharged, and
the truck is driven every day for at least 20 miles and usually much
more than that, rarely is it left a whole day without moving at all
(when left at an airport only). The radio equipment is on all the time
so there is a constant load and it did happen on rare occasions
(airport) that the batteries would get drained completely, but I
consider that typical of what a cruiser does to batteries, sometimes it
just happens. The batteries have been well maintained, I check the
water in them often and replace it as necessary, and the batteries are
sitting on a wooden battery "tray" that I made for them behind the
passenger seat. I wouldn't say they are pampered, but they certainly
are not abused.

Recently these batteries have degraded to the point that they won't run
the radio equipment over an entire night (10 hours let's say) before
they go completely dead. Now of course those "completely dead"
dicharge cycles are rapidly eating the batteries and sucking out what
life they had left in them, because it's a bad thing to completely
discharge lead acid batteries. But they degrade naturally to that
point, that is to say that I didn't suddenly change my habits, they are
being subjected to the same conditions as when they were first
installed in the truck.

This is very similar to experience I have had with lead acid batteries
over my lifetime, but I always thought that they "died" because I
wasn't taken good enough care of them. I'm convinced now, however,
that it really doesn't matter much, that no matter what you do with
deep cycle lead acid batteries they are not going to last more than
about 2 or 3 years, maybe a few years more if you have a really huge
bank that is under a very light load, and maybe a few years more beyond
that if you are using something more substantial than a marine deep
cycle, something made as a UPS backup for example or for unattended
telephone stations. I have started to think that it's best to just
plan on replacing the bank after 3 or 4 years (conservatively) and buy
accordingly. In any mega-store store you can get 100aH 12vdc batteries
for 50$us/each. So for 2000aH at 12vdc that's about 1000$us, amortized
over 3 years let's say, that's about 333$us/year. Compare that with
West Marine AGM 8D batteries in a bank, 180aH per 12vdc battery for
410$us/battery, that comes out by my math to be 2000aH for
4551$us/bank, or about 4 times as expensive as the cheap lead acid
batteries. Are the expensive ones going to last 4 times as long ? Say
that again ... are the expensive AGM marine deep cycle batteries from
West Marine going to last 12 years ? Anyone have experience that says
yes ? They'd have to last that long to give the same cost/benefit.

Do they last that long ? I have my doubts. In fact, I'm starting to
think that the best way to go is to just find a supplier of the
cheapest thick plate lead acid battery you can find and buy your banks
there with the intention of replacing them all after 3 or 4 years.