I have always wondered what would happen to those throw away, "maintenance free sealed lead acid" batteries if one maintained them much like a normal lead acid battery. What kind of lifespan can they have if you bought one brand-new and then maintained it like a regular lead battery?
Well I am going to
answer that question with this
thread.
I have gotten a hold of a fresh batch of brand new AGM (Absorbent Glass Mat) maintenance free sealed lead acid batteries. Due to my background as both a manufacturing tech and a systems admin, I found I have had some very esoteric experiences with these batteries and their maintenance.
For instance, I use to work for a hospital. Even the pencils seem to have a backup battery attached in a hospital environment- so I have had a LOT of
experience with both standard deep cycle, car type batteries and "maintenance free" AGM types. I further maintain a huge UPS and generator where I work now. It's got eight hours just in the batteries alone! Everything except the heat\AC is able to run on the UPS for eight hours before the batteries need charging. (Generator handles main lighting, AC\heating, the elevator, etc.) So suffice to say I have some knowledge to give away when it comes to SLA-AGM batteries and standard deep cycle types.
However, I have stated the above because if someone thinks I am an expert, they will take what I say with a grain of salt. I am NOT an electrical engineer. I am NOT affiliated with a battery company and I have NO specific training- other than from the School of Hard Knocks, with a degree in flying by the seat of one's pants. Essentially, I have a lot of hard won experience with small systems using the equivalent of a car or truck sized battery, as well as the smaller SLA-AGMs used in alarms, emergency lighting and Uninterruptible Power Supplies.
And let me say that I am a HUGE fan of what I call independent systems. Those are small systems using a small
solar cell or other charging system with a small battery. I have found that many small systems is far better than one or two big ones. The obvious reason is that if one system goes kaput, you can quickly swap to another, non-vital system as a replacement.
And it's a LOT cheaper to learn with!
So those of you looking to do
solar, wind, etc, might want to cut your teeth on small stuff like this now. Otherwise, you could make some very costly mistakes with your off grid projects. Small starts = small failures = BIG LEARNING. A 7Ah battery can be replaced for $15 bucks. A small solar charge controller for $20. Start small, learn big. And the small array can charge you electronic stuff during any emergency too.
Ok, so now that my "credentials" have been established as a first
class tinkerer and all around breaker of stuff to learn the hard way expert, I offer my obligatory "Don't kill yourself" warning.
Please DON'T kill yourself!
Batteries of even the supposed sealed type are not really sealed. They emit hydrogen, which means in rare circumstances, they can explode. Never seen it before, except as a young man using what's called a
water welder. Essentially, it is a device that uses hydrogen to develop a really hot, but nearly microscopic, flame. Somebody turned the welder on and then decided to walk away. They came back and lit the flame on the water welder... The tip shot off and did an old west style ricochet off a couple of surfaces- and that was a microscopic welder. So if you try really hard, you can cause an explosion with hydrogen from a battery or break one and spill acid all over the place and you. If you drop one on your foot, you are looking at potentially some serious medical bills and pain. So be careful. But if you simply take a normal amount of care, you won't ever get hurt in any serious way- even by maintaining a maintenance free battery.
WORD OF WARNING!!!
I am confident that if you break the seal of a maintenance free battery, you break the warranty. So be aware that your mistakes are OWNED by you.
Ok, so as to actually maintaining a "Supposedly Sealed Lead Acid" battery, I already wrote up how to do that in a post about how to get these batteries for free and then return them to use here:
https://permies.com/t/84194/Salvaging-Dead-Absorbent-Glass-Mat
Check that out for the actual procedure on how to recover them and maintenance them. The maintenance procedure is the same for new or used SLA's, so not going to repeat that here.
This thread is about making SLA's last as long as possible with some simple maintenance- is that even possible? I will post my results here and share with everybody just how long I can make them last. I have never done this with new SLA-AGM's, but I have with their brothers known as "low maintenance" batteries, car batteries, deep cycle, etc. So this
should be an interesting thread. It's going to take forever and I will post my data here for everyone to see as we go along, but this is potentially really import to off grid users and people wanting to build homebrew power systems.
To start, I have four brand new 7Ah batteries. They are the standard alarm and UPS batteries one sees in common systems. They are cheap to buy- compared to a $150 car battery. Retail auto part stores like O'Rielly's
sell them for $30, but you can get them for $15 on the internet or even less. It's the shipping that kills these things though. Here's a picture.
Now I realize that many know what an Amp Hour is, but many are just starting out. So here is the definition of what an Amp Hour, expressed as Ah, is. Using the 7Ah battery, we can get one hour of use at seven amps from this battery or seven hours of use at one amp. It's not perfect and you will get less than stated, especially as the battery ages, but it is at least a recognized standard for rating capacity.
IMPORTANT
Don't misunderstand that a 7Ah battery is a particular shape or size- it is a power rating only. It refers only to capacity. A 7Ah battery might be round, square or rectangular. That's important if you are replacing your UPS battery. The slots are made for only one size that matches a particular set of dimensions.
I will have these batteries in a system with a 20 Watt, 12V solar panel and a 12V solar charge controller. (Incidentally, this same setup can be used to charge anything that runs off your car battery. Many small systems built to the 12 Volt system of a car will charge in this setup. In an emergency, you can charge your phone, etc with a small mod of this system.)
I will be posting the voltage of each battery after a full charge on the same charger brand new from the factory. They will be "unsealed" and water levels checked and filled before they are charged, so I know I am starting with a good battery and not one that's dry already. (Not a good thing for AGMs or any battery.) I will let each battery sit until the voltage is stable too. (Batteries will lie to you about their voltage when they are hot off the charger.)
I will soon have four of the identical SLA-AGM batteries to test and I will record their voltage levels pre and post charge after making sure water levels are good.
Then out into the garden they go for a month on identical systems.
I will then bring them back to the bench, check them for pre water voltage, then add water if needed and charge them again with the nifty little charge I have. We will keep going like that all through Spring, Summer and Fall until the systems are brought indoors.
That means this thread will be updated every so often with findings. My theory is that I will get over two years out of these batteries and they will still be going near new.
Why?
Because when battery makers test their batteries and claim a two year lifespan, they don't actually do two years of testing. And they don't break them open to see if they need water during the test, because they are maintenance free. Further, they don't actually test them for two years. They set them in a test rig and do a bunch of charge\discharge cycles that simulate two years of real world usage.
Now before anyone thinks that a conspiracy is to be found with maintenance free batteries, let me say this. Yes there is a conspiracy and no there is not. SLA-AGMs are made to be used and then tossed. So all those emergency
lights you see with headlights on them in stores and businesses and such, get replaced by law every two years. That's a lot of batteries!!! They build them as maintenance free - and they are. So they break down at around two years of use. I suppose the "conspiracy" is in the fact that the maker does not want you to crack these open for any reason whatsoever. But they did bill these as maintenance free... And there are some really good reasons why they don't want you to try and maintain them either.
First, you might kill yourself and your widow will sue.
Second, the whole point is that maintenance people don't have to visit these batteries once every three months to add water. They are MAINTENANCE FREE.
Third, the battery companies are happy to sell you new batteries every two years. I don't think that's evil. They bill them as maintenance free and they are. But I do think it's expensive- but not wasteful. Here's why.
The recycle rate on any lead acid battery is really high, likely way above 98%! That's what "core charges" are all about when you replace your old car battery with a new one. So there is really not a conspiracy here.
But there is in my opinion a way to save a LOT of money with just a smidge of time now and then. Time spent taking the batteries out of use and filling them up with water, giving them a good charge and then back into the field. I suspect that with correct use, proper sizing and just a little bit of care, one can easy get five years out of a SLA-AGM battery. And one can repurpose them as they age for smaller and smaller things, like maybe running a night light for
chickens, lol.
So this will be a real experiment, even if it is a small one. As I mentioned, I suspect one can seriously double or even triple the life of a SLA-AGM battery with this method. Granted, it's a tiny sample. But it is as far as I know, the first experiment of its kind.
And I will add more batteries as I get them.
If you have anything you would like to add or questions about SLA-AGMs, just let me know or post to this thread.
JR
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