You could use that as a backup power supply in case of electrical failure but I doubt it would work as a ballast. On a HPS your not only dealing with the basic ballast but also a capacitor(which is more less an electical accumulator) and a starter. I really don't think it'll fly, if it does work, PLEASE post it! I work at a hospital and them things are a dime a dozen.
Psycho4Bud Reviewed by Psycho4Bud on . UPS vs. Ballast question As I have quite the background in computer technical work, I wonder if I may use my APC UPS Backup Pro 280 in lieau of a ballast for now for a few seedlings I have? The UPS is rated for 480 joules, (Output- Output power capacity 280 VA Output power capacity 180 watts Max Configurable Power 280 VA Max Configurable Power 180 watts Nominal output voltage 120V and input- Nominal input voltage 120V Input frequency 50/60 Hz +/- 3 Hz (auto sensing) Input Connection Type Rating: 5