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AC/DCdude17
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I got an old APC Smart UPS that was tossed out apparently because the
owner thought it was broken because it would only run for a few seconds.
Being as old as it is, the battery was shot. I put a new battery in
and it runs to manufacture's specified run time. Although there seems
to be a problem with the low battery indicator and software's runtime
estimate.
The unit is rated to run 650VA 400W.
The interface port is connected to a test computer and a simulated load
of 200W(computer power supply with resistive load to simulate computer
like load)applied under which condition manufacture claims to give 15min
runtime.
The low battery alarm goes off only one minute into battery operation
and tells the computer that is connected to the interface to turn off,
but the simulated load continued to run for 20 minutes, well beyond the
spec.
Other than not being able to tell when the battery is actually low, this
is not a problem when used as a dumb UPS. However, it is a major
problem when I use it with a management software, because it thinks the
battery is low and signals the computer to shut down almost immediately
after power goes out with 90% of battery capacity remaining.
I don't understand how the UPS is detecting low battery. The software
estimates 7 min of run time(which is way off). The estimate changes
with load, so it's measuring the amount of load some how.
Below are the test results of continuously monitoring battery voltage at
the circuit board:
13.95V float voltage at 25°C ambient (isn't this kind of high? I wonder
this is why the installed battery was dead as a brick only after 3 yrs)
Low voltage alarm came on about a minute into battery operation and the
battery voltage was around 12.2V, very health reading for a battery
under load.
UPS cuts off at 10.3V, seems about right.
Voltage drop at the terminal was already eliminated since readings were
taking at the board. I suspected there's something wrong with the
voltage detection, although a reasonable cut off votlage seems to imply
that internal voltage measurement is working fine.
So, I pulled the board out to see if I could somehow change the low
voltage alarm threshold. There is no adjustment trimmer of any kind.
The possible causes I can think of are: Something was programmed
incorrectly through interface, firmware is retarded, out of tolerance
passive components or failing semiconductor parts.
Anyone have any idea what might be wrong with it and how to fix it?
I got an old APC Smart UPS that was tossed out apparently because the
owner thought it was broken because it would only run for a few seconds.
Being as old as it is, the battery was shot. I put a new battery in
and it runs to manufacture's specified run time. Although there seems
to be a problem with the low battery indicator and software's runtime
estimate.
The unit is rated to run 650VA 400W.
The interface port is connected to a test computer and a simulated load
of 200W(computer power supply with resistive load to simulate computer
like load)applied under which condition manufacture claims to give 15min
runtime.
The low battery alarm goes off only one minute into battery operation
and tells the computer that is connected to the interface to turn off,
but the simulated load continued to run for 20 minutes, well beyond the
spec.
Other than not being able to tell when the battery is actually low, this
is not a problem when used as a dumb UPS. However, it is a major
problem when I use it with a management software, because it thinks the
battery is low and signals the computer to shut down almost immediately
after power goes out with 90% of battery capacity remaining.
I don't understand how the UPS is detecting low battery. The software
estimates 7 min of run time(which is way off). The estimate changes
with load, so it's measuring the amount of load some how.
Below are the test results of continuously monitoring battery voltage at
the circuit board:
13.95V float voltage at 25°C ambient (isn't this kind of high? I wonder
this is why the installed battery was dead as a brick only after 3 yrs)
Low voltage alarm came on about a minute into battery operation and the
battery voltage was around 12.2V, very health reading for a battery
under load.
UPS cuts off at 10.3V, seems about right.
Voltage drop at the terminal was already eliminated since readings were
taking at the board. I suspected there's something wrong with the
voltage detection, although a reasonable cut off votlage seems to imply
that internal voltage measurement is working fine.
So, I pulled the board out to see if I could somehow change the low
voltage alarm threshold. There is no adjustment trimmer of any kind.
The possible causes I can think of are: Something was programmed
incorrectly through interface, firmware is retarded, out of tolerance
passive components or failing semiconductor parts.
Anyone have any idea what might be wrong with it and how to fix it?