I work on various alarm systems that use mostly two 12.0 volt 7.0 or 8.0 AH rechargeable lead acid gel cell batteries in series. Although fifteen or so years ago you could get up to ten years out of a typical set of Japanese gel cell batteries, these days it seems that three to five is about all you can expect from the Chinese knock offs that have flooded the market. I used to keep replacements in my van but I found that if they weren't used within a certain time frame they would sulfate. So now I don't keep any of these in stock, instead I buy them as I need them. It's a little more inconvenient but I always get fresh ones this way.

Today I replaced two batteries in a fire alarm panel for a customer. He had bought a case of batteries, he said "a few months ago" and asked me to use his. I used two batteries that he had in stock. The batteries had a 5/13 date code. Although the batteries came right up and worked fine I have to wonder, how well will these two batteries, that have been sitting in a box for over a year perform as compared to two fresh ones? I guess what I'm asking, if anyone knows, how much life span is gone or lost by these batteries just sitting in a box for fourteen months? Thanks, Lenny