D Yuniskis wrote:
Sylvia Else wrote:
Both my old and my new SOLA UPS use a float voltage of 13.5 volts
(near enough), which is at the low end of the battery
manufacturer's recommendation (13.5 to 13.8). I get about three
years out of batteries in the old UPS. Too soon to say about the
new one.
That takes care of one of the killer parameters - float voltage. But
at what rate do they recharge after a serious discharge?
I haven't checked that. My AVO meter apparently has a significant
voltage drop on its current range which messes up the result 
I obtained an ammeter. On both UPSs the initial charge current is less
than one amp. The battery manufacturer's recommended maximum charge
current is more than two amps.
This is not that surprising. Providing a large charging current would
involve more expensive components, and provide limited real benefit.
I had argued that UPS manufacturers would err in favor of
faster charge times just to reduce the user's perceived
"exposure" *after* an outage. I.e., the available up-time
from the UPS shortly after an outage is obviously MUCH less
than the up-time available at the start of that immediately
previous outage (because the battery now has less reserves).
If a second outage followed the first before the battery
was able to recover substantial capacity, the user would
be disappointed in how "crappy" the UPS's performance was
Unless outages are that frequent, I wouldn't have thought that enough
users would experience this problem often enough for it to impact on the
manufacturer's reputation, particularly as anyone hearing the complaint
would tend to express the "what did you expect" response.
The extra cost of the components required to obviate this to some extent
would weight heavily on the manufacturer's mind.
Sure, the user would expect the UPS to be unable to maintain
the load for the full duration *shortly* after an outage...
but, how long does the user's acceptance of this reduced
capacity extend *after* such an outage? Surely, the next
*day* the user would expect the UPS to behave AS IF there
had never been a previous outage! But, how would they
feel about it 12 hours after the first outage? 6 hours? etc.
So the net result is that neither of my UPSs is using an excessive
float charge voltage, nor an excessive charge current, but I still
only see three years life out of the batteries.
grin I don't have much "sympathy" for you there! That's
sort of like complaining that you only had *two* dates for
the high school PROM... :-/
I think I've been lucky to get *perhaps* two years out of
batteries. Of course, that's reflecting the batteries that
I have discarded because the UPS "told me" they were bad
(idiot light) *plus* those that I was able to LEARN were
bad based on empirical evidence: they didn't hold up the load
when there *was* an outage!
My "three" years is based on throwing them out when the UPS says they're
no good. As I've indicated, they're far from being dead at that point.
I should note that I don't usually run them down far during outages. My
philosophy is that if the power isn't back within a couple of minutes,
it's probably something that'll take longer to fix than the UPS can
handle, and the UPS is directed to turn off. This gives me time to save
work, etc, if I'm actually doing something at the time.
I don't think there's been an outage where the UPS got turned off, but
the power returned within the time that the UPS could have run.
I will be curious to see how life expectancy is affected by
NOT leaving the UPS's running unless their loads were also
"on"...
It's far from clear that that's a good idea. Instead of a float charge,
you're exposing the batteries to self-discharge for a period, followed
by a higher chargin current for a while.
Sylvia.