sorry for bumping 
I would like to buy this driver but need to know its’ efficiency first.
Richie086, according to your info on the other post
quote: “With the XM-L2, tail cap measurements were 2.24a on high mode.”
I just tried to calculate the efficiency @ xm-l2, correct me if I wrong.
Output to led: 5A
LED nominal vf: 3.24v (accord. to datasheet ?)
Power to LED= 5A*3.24V = 16.2W
Output to driver: 4.19V*2 = 8.38V @ 2.24A
Power to driver = 18.77W
~Efficiency = 16.2/18.77=~86%
Is that right 
?