how to calculate Universal Power Supply requirements?
 

I need to supply power to a 800w unit via batteries. 800w/12v = 66amps. I need the system to be able to go 12 hours before the batteries get recharged.

66a x 12h = 800 amp hours.

What spec batteries do I get?

800 amp hours sounds enormous - are you sure its calculated right?

nope, not sure at all! I could be doing it entirely wrong.

Here's what I figured-

I know the wattage total for the computer = 800w and I think I'm supposed to divide that by the power source voltage, which is 12v batteries. that = the 66amps needed, I assume that is per hour. And I need that to run for 12 hours. so I figured 66amps an hour x 12 hours = 800 amps.

Well I just asked someone and the 800 is correct

BUT

they've now added on that the inverter will add to the consumption PLUS when the batteries drain the voltage will drop and you're going to need extra to counteract both of those things and having it all explained to me has confuzzled me even more :(

that's where I'm at! I spoke with cs of the converter/charger manufacturer and they helped add that in, which is how I derived the 800w total but the battery cs gal can't seem to help me with which batteries satisfy the requirement. she recommended an 18amp battery.

the inverter/charger is 1000w supply.