D Yuniskis wrote:
Hi,

I don't have anything other than "gut feel" to resort to
as evidence but it sure *seems* like most UPS designs
EAT batteries!

My empirical experience is that there are three issues he

1. UPS quality. I mostly use APC units, and the cheap desktop BackUPS
units do seem to destroy batteries faster than the more expensive
SmartUPS units meant for servers.

2. Temperature. If it's hot in the server rack the batteries will die
an early death.

3. Charge/discharge cycles. More and/or deeper cycles will kill the
batteries faster.

I've worked at two sites that had APC SmartUPS 3000 XL units. These are
3 kVA rack-mount UPSs that take eight 12V gel cells in series-parallel
to make a 48V pack.

At the first site, the server room was pretty hot and the power was
really unreliable. We'd fully discharge the pack every couple of months
on average. Typical battery pack temperatures were around 100 F. We
were putting in new batteries every two to three years.

At the second site, we practically never had outages and the server room
was relatively cool. We got five years out of those batteries before
the voltage started to drop precipitously during the weekly self tests.

BTW, some of the early SmartUPS 3000 units don't use a battery tray and
have all the batteries slide into the front of the UPS single-file.
It's a hell of a job to change them out when a battery fails and swells
up, wedging itself in place! Later ones have a removable
tray/cartridge, much easier.