I couldn't resist that $12 deal as I really like the C3 (I did some testing on a previous purchase but gave that unit away).
I measured 4.4A on a 25R, ~1600 lumens plus a proving ground comparison showed me it's between 1500-2000 lumens. The output is consistent on the two units I have/had. As for the overcharging, the indicator light turns green at 4V and I may just have to charge any batteries for it with a separate charger when I can't keep an eye on it.