Ed from Ed I just picked up a apc bk500. I charged it most of the night
and the voltage only shows 98 volt on battery. The instructions on the
internet show some sort of cd disc for windows which I do not have with
a good battery can I just use it as it is for a usp for the computer.
no alarm led lights on and it appears to be working fine thanks Ed

I'm not aware of the inner workings of these things, Ed, nor have I put an
AC voltmeter on the output, running off the car battery, to see what actual
voltage I'm getting. The computer runs fine off of it but now you have my
curiosity going.

It might be worth re-checking the AC output voltage using a voltmeter
which reads "true RMS". Most inexpensive voltmeters actually read the
peak voltage, and display an RMS value calculated based on the
assumption that the waveform is sinusoidal.

A lot of backup power supplies use inverters that create a distinctly
non-sinusoidal waveform... it's sometimes a square wave, and sometimes
a "stepped" waveform which crudely approximates a sinusoid.

It's entirely possible that the APC BK500 creates a non-sinusoidal
waveform, whose RMS value is close to the nominal 120 VAC, but whose
peak voltage is lower than that of a true sinusoid having 120 VAC RMS.
This could cause most inexpensive voltmeters to read a value that's
too low.

--
Dave Platt AE6EO
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