TK 11 on rcr123s

I run my TK11 on protected ultrafire 18650s but i noticed the other day when i put a couple of old unprotected rcr123s in that it was noticably brighter.

The ultrafire 18650s seem ok,i've just checked the voltage of one that was last charged a month ago and it reads 4.08v.

Questions are ,Is it normal for tk11 to be brighter on 2x rcr123s or 1 x 18650? should it even make a difference? are my ultrafires shot? and if I were to buy and run it on AW rcr123's how long will they last on full power ?

TIA Geoff

2 RCR 123's will be twice the voltage of one 18650 so yes it will be brighter this is normal
18650 will give you longer runtime however I am unfamilar with the TK 11 is it optimised for 18650's?
Is the TK 11 safe at 8 volts?

Mike

I am assuming that the TK 11 is regulated?

If i can run my pd30 on 2xrcr123s i am also assuming that I can run the TK on the same?