12 volt battery question please

wa8yxm wrote:

Gdetrailer wrote:
I have a bunch of UPS units around my house, they all came equipped with AGM instead of Gel cells, life of AGMs in "standby use" is far shorter than Gel cells. Older UPS units which came with Gelcells battery life was 5-6 yrs, the newer units equipped with AGMs I end up changing out 2-3 yrs..

I have used both AGM and GEL and I've seen others
Gel is the finikiest eater of any battery out there. You need to be very very very careful charging them.. AGM's on the other hand are gluttons. you can feed them fast enough to "Choke a horse"

(From Xantrex and Lifeline,
Regular Lead acid should be charged 0.30C or slower (C is capacity in amp hours at the 20 hour rate so a 100 amp hour battery eats no more than 30 amps)

Gel 0.25C

Agm.. over 0.2 C used to be 0.3 C but they lowered it And top charge rate easily 2x the minimum (Note with AGM we changed from MAX to MIN charge rate)

I've seen AGM's go 12 years.. I've had 'em last 5, I've never had a gel make it to 2 ANd that was in a system specifically designed to use GEL batteries.

I have three UPS units which came equipped with AGM batteries, I CAN assure you, AGMs do not ALWAYS last or are better than the older UPSs that had Gel cells.. As I mentioned, the UPS units I have with AGMs only get 2-3 yrs of service, IF I am lucky, my older UPS units which came with Gel cells typically get 5-6 yrs..

Not to mention a company I worked for had built a mobile computerized product for industrial use in 24/7/365 environment.. The engineers decided on AGMs instead of Gel cells, equipped with a charger designed exclusively for AGMs.. The onboard computer also had a battery monitor interface that allowed the computer let user know when the device needed to be plugged in to charge.

That product was a total flop due to the battery.. Our Service department sent out replacement batteries like they were Tic-Tacs.. But they were not as cheap as Tic-Tacs at $150 per battery with only 24 Ahr capacity.. Gel cell of same capacity would have only cost $50 and lasted just as long or even longer..

And by the way, I have seen bloated AGMs, you CAN feed them TOO MUCH at one time.

Nothing special about AGMs, they share very similar traits to a Gel cell as both are electrolyte starved system. Both AGM and Gel cells tend to suddenly fall off the cliff and die without any signs of failing. One day they work and the next 100% stone dead.. FLAs do not do that, they typically will give you warnings of reduced capacity.

I also worked with another industrial device which used Lithium batteries.. Yeah the stories I wished I could tell of those.. We had to stock hundreds of those batteries and I was the poor sap that had to deal with repairing/refurbing/reloading/replacing those devices..

The batteries were great up to the point that the BMS failed and cut off the battery power for no reason causing a lot of battery replacements..

Then there was those batteries with BMS failures that failed in a different way, shorting out the battery causing the device to overheat enough to give a few customers severe burns.. Needless to say, company withdrew that product and canned the entire project.

I have a huge respect for those batteries, when they work they are nice, but when they fail, the results are less than pretty.