Wow--the light landscape has changed since I was last active here in 2003.
Hello rlhess,
The answer to your question about the KX2C is yes, it will work with a 17670; but no, it will not work
well. I have an E2DL, which utilizes the KX2C head. I bought it assuming that I would be able to use the same Pila 168s I had been using with my Surefire L4 for years. Turns out that the two lights have different types of regulation circuitry inside, and while the 3.7 volts working voltage of the Pila 168 is enough to keep the L4 running in full regulation, it only allows the KX2C to run at about 70 lumens or so of output. It looks much dimmer than when run on 2 CR123 primary batteries.
I, much like you, had not kept up with CPF since sometime late in 2004. I had come looking for information about the feasibility of running an L4 on rechargeable batteries. I researched the info I was looking for, bought an L4 and some Pila 168s and a charger, and largely quit visiting the forum except for on occasion. After coming back to CPF this January to research rechargeable options for my newly purchased E2DL, I now can't seem to quit.
My opinion on the KX2C head is spend the $109.00 on it. I looked at your web page; you seem to enjoy quality lights. I purchased my E2DL because after looking at some beamshots and a couple of youtube videos, I could tell that the thing had more throw than any other Surefire LED light to date. I was hoping to be able to use it in place of my MagCharger, and as it turns out, I mostly do. It is definitely a "wow" light. It will blow away your L6 for throw.
About the new 17670 cells you are ordering; things have indeed changed a lot in the last 5 years. The Pila 168Ss, and the newer, slightly changed and renamed Pila 600Ss, are neither available anymore. The highest quality substitute readily available now is the AW brand 17670 with PCB protection. However, don't expect to get 5 years of use out of them like you have with your Pilas if you are using a Pila BC-2 charger, as I suspect you are. These were replaced by Pila with the newer Pila IBC charger model about two and a half years ago (at the same time Pila replaced the 168S with the 600S). The older BC-2 charger does not terminate charging when the cell reaches the proper voltage. It continues to supply voltage indefinitely and forces the PCB protection circuit of the battery to prevent any more voltage from getting thru. According to one of the battery experts around here who goes by the username "Silverfox", this worked fine with the hearty PCB of the 168Ss but was somewhat taxing on the newer less robust PCB of the 600Ss. This prompted Pila to come out with the IBC charger, which terminates charging on its own at the appropriate voltage. It's reasonable to assume that the BC-2 charger would also be rather taxing on the PCB of the AW brand cells as well, leading to PCB failure in a shorter than normal time. The rule of thumb seems to be that the chemistry in LiIon cells lasts about 4 years, although I have gotten 4 1/2 years out of mine and you have gotten 5 from yours. The Pila IBC charger costs about $50.00, but there are $20.00 chargers out there which also terminate charging at proper voltage, maybe just not as accurately.
But alas, if I've convinced you to go with the KX2C head, you don't need the 17670s anyhow. What you do need are 2 AW brand 3.7v RCR123s. These are what I have been running in my E2DL since Christmas (about 25 discharge cycles so far). These also should not be charged on the Pila BC-2 due to its putting out too much current while charging, as well as the PCB issues, but can be charged with the Pila IBC and spacers, or with a $13.00 Ultrafire model #138 charger. The KX2C head will run for 62 minutes at full brightness with these batteries, until their PCB kicks in due to low voltage and the light goes dark. Some people here have raised concerns that the 3.7v RCR123s supply too much voltage to the KX2C; thought neither my brother nor I have had any trouble with either of our lights, nor have the many other people on the forum who are using this same set-up. However, if you wish to play it ultra safe, then you can use 2 AW brand 3.0v LiFePO4 123s for about 36 minutes of runtime at full brightness. These cells can be charged with the above mentioned Ultrafire charger set at its 3.0 volt setting, but not with the Pila IBC.
some links for clarification:
enter coupon code CPF for 2% discount at Lighthound:
http://www.lighthound.com/AW-17670-Protected-Rechargeable-Lithium-Battery_p_101.html
http://www.flashlightz.com/product.php?product=171829
http://www.lighthound.com/AW-RCR123a-Protected-750-mAh-Battery_p_114.html
http://www.lighthound.com/AW-LiFePO4-3-Volt-Lithium-Rechargeable-Battery_p_112.html
http://www.lighthound.com/Ultrafire-36-volt-or-3-volt-RCR123-Lithium-Battery-Charger_p_2270.html