Love my T20 Q5. A 18650 won't fit, either protected or unprotected. I have both protected and unprotected AW 17670's that I got from Lighthound. Only the unprotected cells fit at the moment, I'm going to burnish the inside of the tube with some sandpaper and see if I can't slide the protected cell in. On a 17670, my experience has been that it will open up on high sometimes (but only run there for 15-20 minutes, then you have to switch to level 2), sometimes only on level 2 and stay there. The light won't switch levels, you get level 2. Level 2 is 120 lumens, about what I use at night when I walk, I rarely need high. It'll strobe on high fine. AW's 17670's last for about 1.75 hours before dimming a little. It'll start low voltage strobe after about 2 hours. My batteries are pretty new, they might not last as long after some use. Since they fit tight in the tube, you have to make sure that they fit against the positive contact, the spring isn't strong enough to push the battery up the tube. A magnet or a "button" isn't needed. Now for the good news.
Use the AW protected RCR123's from Lighthound. They work fine. When done, they actually shut the light down. No low voltage strobe, just poof. They give me about 2.25 hours on level 2, and just about an hour on high. Works for me. I've used unprotected Powerizers (white and orange) and Ultrafire 800 mah (green) cells and the light does give you a low voltage strobe when it's time to decrease levels, batteries are almost done anyway. It's your choice, I voltage match my batteries, used in pairs they have treated me well so far, but I monitor them pretty closely.
If you do choose to use protected batteries, remember that if you drop them you can damage the protection circuit and they may still work, but aren't protected. My AW's terminate charge at 4.25 volts - period, I am going to assume if they ever don't, they're bad and I will dispose of that cell.
I think you'll like the Olight, it's a fine Christmas present to yourself. :thumbsup:
