If you have computers or electronics that you don’t want to be killed by power fluctuations, it’s a good idea to have a UPS (Uninterruptible Power Supply). The battery in the UPS keeps your equipment running through blackouts our brownouts (reduced power).
Dead Battery
The main problem with a UPS is that its battery might only last a couple of years. A dead battery is often announced by a UPS through regular beeping. Because a UPS is expensive, consider just replacing the battery instead of the whole UPS when the battery dies.
You can buy a replacement from the UPS company or for significantly less money from a third party such as Battery Mart. Just be sure to get a battery that is designed for your specific UPS. I have had good luck with with Battery Mart, but there are some third party batteries which are of poor quality, possibly having a short life, acid leakage, or even causing a fire.
I replaced the battery for the APC Back-UPS 500 ES for $26.39 from Battery Mart instead of $48.99 from APC (prices include shipping).
APC batteries cost more because they (normally) come with better warranties, guaranteed compatible specifications and they will recycle your old battery for free. Plus they have technical support.
I’m not saying that these features make them worthwhile but that’s what i have come up with as the reason.
note: I am not affiliated with APC in any way