Rechargeable batteries for ultrafire flashlights

I put a rechargeable battery 17670 to my two led flashlights : ultrafire C3 and B1. They both shone as bright as ever but when I put back the original normal AA batteries in them they just didn't shine as bright as before (with AA battery).
Has anyone got the same experience and what had happeded to the led bulbs?

Hmm, a UltraFire C3 should be rated up to 4.2V.

So this sounds weird

Questions:
- How much volt does your 17670 give off ?
- You used a -single- 17670 right ?
- How long did you run it on the 17670, have you had it on for very long, minutes, 10s of minutes, a hour?
- Has it gotten very warm ?

I've got a DealExtreme ultrafire C3, and have it powered up to 3.6Volts, and I can say that:
A. It doesn't shine any brighter at 3.6 volt compared to 1.2 volt.
B. It seems fine after the 3.6 volt when it's back on 1.2 volt single AA.

Mayby if you can answer the questions we can give a better answer to yours

I am interested, cause I'd like to prevent similar problems with mine

Corrections. It was a 14500 3.6V/900mAH (I was using 17670 for my P3D only)

# 3.6V
# single 14500
# only turned on for 2 minutes
# it was a little bit warm

My C3 was newly bought and that was the first time I charged it with rechargeable batteries.
(It seems better now. The difference is not so big as the first time.
I think this could be the problem with the new bulb.)

Thanks.