In my post I mean the combination of gen1.3 (SF L2 and R5 Drop-In) - sorry for my unclear post.
For full brightness of a XM-L you need about 3A. Sometimes cheap batteries do not offer 3A. Another point is the missing protection of the battery. If the batteries support 3A and the Ultrafire XM-L drop-in do not turn off by low voltage, you can damage your battery.