Originally Posted by
hamster
First link mentions 4*18650 batteries. That's 14 Wh. They are claiming 2-3 hours of 1800 lumen on 14 Wh of charge (250 to 380 lumen/watt). That's thoroughly implausible. Either the brightness or the life expectancy is lower. And it apparently weighs 275 g. $51 is more than what I paid for my Cygolite, which weighs 110(ish) g.
Real world is 1200-1300 lumens. I'm in Canada, all cygolite metro series are $60 and above here. The point is: usb isn't the de facto standard for mid range lights, 60 lumens per watt is 5 years ago, there are much better deals than buying a cygolite or niterider (or any lights offered by your lbs). I haven't bought any lights from a bike shop since they just don't pass the lumens per dollar ratio, but I do go in from time to time to see what's being offered.