Hi Paul.
A large car battery would last several days. We use sealed gel batteries, but many use small sealed motorcycle batteries.
Our batt’s are rated at 33 amp hours and my digital voltmeter tells me this should last about 40-45 hours.
Which also says I could use smaller bat’s. Best practice is to charge them each night after use. They are not like ni-cad’s and have no memory effect.
LED’s burning 2 strips use about 1/2 to 2/3 the power of a single fluorescent bulb meant to run on 12 volts.
I’m showing about .7 amp for 2 strips.
Get a dimmer and its even less.

David, thanks for your question. I can only recommend the PRO PDR solutions
light, in good faith, since its only ones I have purchased thus far.
My good friend Jeremy just bought the Ultra LED Light and he says its better.
I trust his opinion and I will be ordering the Ultra very soon.