Simple except for one missing piece of info. How efficent is the system ?
The Ah (amps the battery can put out for one hour). As Amps and voltage equals watts, your battery is rated for 12 times 18 or 216 watts for one hour. So you get 216 devided by 120 or 1.8 hours. Then multiply by the efficency (loss of the system) that is unknown, but 50 to 80 percent would be inthe ball park. So at 50 % you get half of the 1.8 hours or .9 hour.
All that is provided the battery can put out enough current to last that long. Often the more current the battery is required to put out, the less time it will last.
UPS batteries have to provide the magnetizing current for the big iron transformer, so battery life is disappointing at light loads. Nowhere near as good as a DC-DC converter.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.