I really don't remember. I don't think I ever tested it. I was using it at the same time as the Knog Blinder 4V and I always take all my lights off at once when charging any of them, because I can't keep straight "OK, I charged the Cygolite on Tuesday, it lasts 6 days, the Knog on Monday, it lasts 3, so I should charge this on October 43rd, carry the 6...."

The Knog has the worst battery life of any light I've owned, I have to charge it twice a week, so everything got charged twice a week.

Anyway, this is from their web page. It doesn't sound wrong to me. Probably the Serfas wouldn't last that much longer than the Knog, I usually ran it on bright flashing.

Run Times: (60 lumens = 2.4 hours; 35 lumens =5 hours; 60 lumens flashing = 4.5 hours; 35 lumens flashing = 14 hours)