Best Answer phil_m , 23 July 2013 - 05:25 AM
When you look at portable battery packs, you'll see them rated in amp-hours, or AH. That will give you an idea of long they can power a certain load. I'll use this one as an example. It has a rating of 12 AH, and its terminal voltage is 12V DC.
The HD500 power supply is rated at 2500mA at 9V, so let's assume the HD500 actually runs at 80% of that. That means the HD500 consumes 18W. At 12V, the current drawn by the HD500 would be 1.5A. So 12AH/1.5A = 8 hours. So at you could expect about 8 hours from that battery pack. But even then, that's assuming a pretty linear performance of the battery. In real batteries don't necessarily perform that way, but that's how you could get an idea of your run time. It's also ignoring the fact that there's probably some internal losses inside a battery pack like that when you transform the voltage from 12V DC to 120V AC.Go to the full post