Welcome to CPF Neil,
I'm a recently "enlightened" newbie too, I've been a forum member since early February 2006. My first really good flashlight was a SureFire 6P - the aluminum version of your G2. As you can see from my signature, I've taken a full body plunge into this hobby - much to the chagrin of my wife I might add!
Like you, I developed an interest in rechargeable batteries and high output lamp assemblies soon after getting my first SureFire. There is a wealth of good information on CPF about these topics and I highly recommend that you take advantage of it and educate yourself. "Free Lumens" go a long way toward increasing the utility of your high output flashlights as well as eliminate any financial inhibitions you may have about feeding them!
Rechargeable Li-ion batteries are very different from conventional Ni-Cad and Ni-MH batteries and have unique charging and discharging requirements. The come in variety of different sizes and charge capacities. There are also "protected" and "unprotected" Li-ion's and both types have their advantages as well as their limitations. You'll need a dedicated Li-ion "Smart Charger" in order to safely charge your Li-ion batteries.
Probably the most important concept to understand before using rechargeable Li-ion's in your SureFire G2 is that the rechargeables have a higher output voltage than primary CR123 batteries. Most rechargeable Li-ions measure 3.6 V versus primary (non-rechargeable) 123's which measure 3V. In fact, many rechargeable Li-ions will measure 4.2V (or higher) fresh of the charger. This means that if you load two freshly charged RCR123a batteries into your SF G2 and press the tail switch, you will be delivering a full 8.4V (possibly more) to your P60 Lamp Assembly's Xenon bulb! At $17.00 per SF P60 (or $25 per P61), this can get expensive.
In order to run 3.6V Li-ion rechargeables in your SF G2, you'll need to upgrade your Lamp Assembly to a 9V unit. There are many high quality aftermarket SF compatible Lamp Assemblies to choose from. The most popular ones with CPF members seem to be the G&P G90, DigiLight DRB-9VHP, Wolf Eyes D26 9V and Pila GL3. There are also LED replacements such as the BugOutGearUSA 3W LED Drop-in. These components are offered by a number of very reputable Internet retailers and some of them offer discounts to CPF members (hint: see greenLED's CPF Discount Thread).
I bought my first rechargeable "kit" from LightHound. He sells a bundled package that consists of a G&P G90 9V Lamp Assembly, DSD Li-ion Smart Charger and two (2) Unprotected LIR123a 3.6V 800mAh Li-ion batteries. This is everything you need to join the "Free Lumens" movement. Now, the G&P G90 is not the brightest 9V Lamp Assembly (approx 105 lumens) but it is noticeably brighter and whiter than the P60 Lamp Assembly that came with my SF 6P (the same lamp that you now have in your SF G2).
If you must have the brightest SF compatible 9V Lamp Assembly, it's the general consensus of the Hotwires on CPF that the DigiLight DRB-9VHP at 175 lumens is the brightest. However, I now own both a G&P G90 (105 lumens) and a DigiLight DRB-9VHP (175 lumens) and in my humble subjective opinion, there's not a lot of real-world difference between these two lamps when used outside. Yes, you can see a noticeable difference on your living room ceiling - the DigiLight seems to have a whiter, slightly larger hotspot - but I find no real usable difference between the G&P and DigiLight lamps in my back yard.
Good luck in your pursuit of modifications for your SF G2 Neil. You're on your way to becoming a Hotwire yourself and catching the flashaholic bug. Have fun!
) and except your website (DigilightUSA.com) it's hard to find a G90 Hp and be sure of the HP version (on ebay or other websites)
