I got my junked uninterruptible power supply 4 years ago. It was rolled out because of the bad batteries. Fortunately I had 2 working batteries for alarm system which fitted well in the UPS later. Those batteries now at the age of 5 or 6. I’m still grateful they lasted until now. The recommended battery renewing is in every 2 years. So I’m happy. I haven’t done the renewing since I don’t have redundant UPS system. Once I pull out the plug all computers will stop until I’m done with the battery exchange. I’m running the “farm” without UPS now. It’s quite risky for the raid system I have. But hope we won’t have a blackout until I come back from holiday. Anyway, this will cost me another 50 bucks for the 2 new batteries. Your guess was right, I will buy them again in an alarm workshop. Hail to the brave batteries. Rest in peace guys.