Need teaching on Battery Backup voltage or amp

[Toddskins]

I used to know the answer to this question, but have since forgot.

When buying, for example, an APC battery backup rated at 1500VA, I know that the higher the number it has, the more power it supplies to equipment.

But, there is some math involved when plugging your important equipment into the battery supplied outlets, that you use to determine if you are over the limit.

Do you count the amps on the back of your electrical devices, or the voltage?

And like on the back of my synthesizers, there are several different ratings listed. Which do you use?

Example on my Novation:

90 - 260 volts
50 - 60 Hz
40 VA


So on a 1500VA battery backup, how many of these Novations could theoretically be plugged into the unit and have some protection for a few minutes?


My Kitchen-Aid blender reads 4.5 amps. How would that number be used in the equation?