UPS Battery Float Voltage Low

[Krankshaft]

So I decided to check my APC XS 900 today to see what it's float voltage was.

The charger is outputting 26.32 volts since there are two 12 volt batteries in series divide that by two and you get 13.16 volts per battery. Or 2.19 volts per cell (6 cells in a 12 volt battery).

Now the standby (not cyclic) float voltage recommended for an AGM SLA is about 13.5-13.8 volts. They vary slightly but as a rule of thumb those values are pretty close.

How critical is this voltage exactly?

Is .34 volts really going to have a noticeable affect on battery life?

I know too low a charging voltage can cause premature sulfation. But that is just over 1/4 of a volt of deviation.

[kc8adu]

Re: UPS Battery Float Voltage Low

batteries with high leakage overloading the charger?
measure the charging current.
had an optima red top do that on a ups.
it was used when i got it from a car we bought for parts.
it started a 460 ford with no problem so i used it on the ups.
i thought i had a charger issue in my apc 650 but i noticed the regulator was real hot.
put the red top on my automatic charger to top it off but when it hit about 13.3 it stopped climbing,current draw increased,and it got hot.
once an agm gets abused they do this.a guy from mk battery explained it as microscopic dendrite growth through the seperator.