# Calculate the UPS Capacity in amp-hours [closed]

I am trying to find out the UPS capacity in amp-hours for my HP UPS system. I've already done some calculations based on the UPS information from the HP Power Manager software.

Bellow are my calculations but somehow I doubt them and I think I am making a mistake somewhere:

Output Power: 1160W
Output Voltage: 235V
Run time remaining: 12min - Converted to hours that is 0.2h

First I am converting the W to A:
1160W / 235V = 4.936A

Now to find the amp-hours for 12min that are specified in the run time remaining:

4.936A * 0.2h = 0.987Ah

Can someone more experienced in batteries, current and UPS Systems tell me if my calculations are correct?

I am not sure that I have taken the correct values into consideration since my calculations are based upon the output values from the UPS.
Also as a side note I must tell you that I am not very fond of current and all that stuff and I have only basic knowledge about amps, volts and watts from college.

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## closed as too localized by Qmechanic♦, David Z♦Oct 21 '12 at 9:47

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You have a typo that the Amperes output is 4.936, but that is corrected later on. You also slipped a decimal when you did 4.936 * 0.2, which should give 0.9872. The battery is at 130V, so the current out of the battery is $\frac {235}{130}\cdot 4.936=8.922$ and it is really a little higher for the losses in the conversion. Let's say it is 9A out of the battery. Then you would have 1.8 A-hr in the battery to run for 12 minutes. I don't see where it says you can in fact run for an hour, so it looks to me like about 1.8 A-hr. If you can run for an hour, it would be 9 A-hr.