Shortly after placing the superbrightleds.com order for the two 27W LED lamps I noticed something strange on the website.. that the actual power draw was only 13W? This upset me a bit for two reasons.

1. My price comparison is bunk. Maybe I didn't select the best deal?

2. I could have bought less battery for my goal of 2 hour run time.

I fired up the tech support chat and.. well the guy tried to school me on how to calculate watts. I was not amused. The mystery went unsolved until I received the order.

Using a lab supply of decent enough accuracy I determined the power draw to be closer to 18W. OK, so that doesn't actually answer anything. But I can say that it's bright enough to turn my office into daylight.

At $50ea they weren't that cheap but so far I'm glad I went this route instead of trying to put together discrete LED's. There's a built-in constant current driver which accepts a large Vin range and a nice weatherproof housing.. 

When I got the battery I ran both lights from full charge till it quit. The rating is 10Ah / 128Wh, and it lasted 3.35hr. 128Wh/3.35h=38.2W (19.1W per light). That's a little higher than my measurement but in the right ballpark. You know how those battery ratings can be. 

So, bad news is it's not quite as bright as I had planned on, good news is we have time for another 2 games.

Batt V started at 13.2V and drained to 12.7V and a fairly linear rate.

updated with more pics: