Okay, I've tried to browse for this, but I can't find enough information to get a definitive answer. The Cree R5 is rated at 3.6-18v working voltage, but the the seller also says 3.6-8.4v Working current is 450-600mah Now is the max cr123 in series to add up to < 8.4 or
What is your question? Your post is filled with terms and figures that don't make much sense.
"Cree R5" is a meaningless term if you think you are referring to an LED or a SureFire drop-in . R5 is a flux bin rating. Cree is a company. It's like saying "Ford 302", thinking you are talking about a Mustang.
Presumably, you are referring to a Cree XP-G or similar generation LED. Those had roughly a forward voltage of around 3.3V when driven at the rated max forward current of 1A.
Your term "working voltage" has little to do with the LED. No doubt, that is the input voltage rating of the driver that powers the LED. The working voltage can be just about anything. It simply depends on what driver is being used. Thus, a seller claiming 3.6V to 8.4V "working voltage" could be entirely correct. His product probably uses a different driver than the product that is rated at 3.6V to 18V.
Similarly, "working current" depends on the driver. It could very well be in the 450mA to 600mA range. Or it could be 1000mA. Or something else.
If you are wondering how many 123A Li primary cells you can use before reaching the driver's max input voltage, it depends on what driver is being used. If someone claims that their product has a voltage input range of 3.6V to 8.4V, then absent any other knowledge about the product, that is the input voltage range that you have to go with. How can someone possibly know anything more about a driver without seeing it, knowing what brand of SureFire drop-in it is, seeing test results, datasheets, etc? Someone is selling a laptop computer. He claims it uses an Intel Razz-Ma-Tazz CPU rated at 3 GHz clock speed. Is this correct? How can anyone possibly know the answer to that without seeing the computer first or knowing the brand and model of the computer?