I assume you are aware of it but for the sake of completion, battery runtimes are sold in amp hours AT THE RATED VOLTAGE FOR THE BATTERY - so you will need to multiply the AH by the voltage of the battery to get the the watt hours - which is more useful. Most UPS manuals will have runtimes at various loads documented. I am trying to set up UPS shipping API in OpenCart but getting an error of 250003 Invalid Access License number I downloaded the UPS shipping development kit from the official site of UPS.

Understanding the Context