Re: Can I run L91\'s in my SL 3AA lux?
Not my light, but I suspect the lithium L91's are NOT the problem, NiMh and NiCd's are. The lamp probably depends to some extent on the internal resistance of the battery to limit current flow. The NiMh and NiCd's have exceptionally low internal resistance, and if feed directly the LED, might be able to seriously overdrive them.
Similar story in camera's. Early Motor Driver specifically prohibited the use of NiCd's. Seems the camera depended on the internal resistance of the batteries to limit power to the drive motor. When it came to the end of the film, the limit caused the motor to stall, and that marked the end of the reel. When you used NiCd's, they had such low internal resistance that they could deliver much more power to the motor, and instead of stalling, it either ripped the film sprockets, or ripped the film right off the spool!
The 1.5 volt Lithium Iron Dispulphide battery chemisty has resistance that is only slighly lower then alkalines, but probably still well above what you get out of NiCd's...