"aurgathor" wrote in news:1101846497.
+qTM7IprdMZa0wGRZUm5Zw@teranews:

BTW, how do these sealed batteries degrade? Is it sulfating,
or something else? Is there any way to reverse it to some
degree, like charging it with a slightly higher current and/or
voltage, or pulsing it? Again, if the batteries are not 100%
and I only get half of the runtime -- I don't care. But waking
up in the middle of the night because my UPS is beeping
can be highly irritating. :-(

One of the 12 cells of your batteries was overcharged - and is
destroyed. Unfortunately you can not replace this cell in a sealed lead
acid battery. Other methods of repairing it are not possible.
Batteries in UPS degrade mostly because the cells are not balanced.
All are connected in series, and over time the voltage over the cells
is getting different - because of little mechanical or chemical
differences in each cell.
You can increase the lifetime by lowering the charge voltage. Normally
this is 2.3 volts per cell (or 27.4 for 12). Lowering this to 2.27 will
reduce the available capacity a little, but the lifetime a lot.
But the problem is - how can it be changed in the UPS?

Another way would be a balancing circuit for each cell (ensure that
each cell has no more than 2.3 volts). But with the sealed batteries
you have no access to the connectors of each cell.

Sulfating is another issue, but this takes much longer at room
temperature. I have a torch with a sealed lead acid battery that I
charge once a year. It is still ok! The sulfating is also regularly
removed by the test cycle of the UPS (if there is any) or some drop
outs.

M.
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