Promotion on Dino Direct at the mo... blue Ultrafire 18650s are $8.40 for 4, look to be protected. Don't know what the quality of these is like but at $2.10 they are the cheapest 18650s I have seen.
Heres the link: http://www.dinodirect.com/lithium-rechargeable-battery-2400mah.html
If they were the same as the ones they sent with the 502b and charger than i'd say they aren't bad ...(i'm sure i'll be editing this post as i have no way of testing these and their true potential )...
i'll hedge my bet and say that spending a little more for a better battery is probably a much better idea .Buying cheap batteries is always a bad idea ..But ...if you're selling a light and are tossing in a battery it seems to be a decent battery to give away
Get better batteries period. Those ultrasomethign blue could be anything but certainly nothing to brag about. As far safety in li-ion is somehow important to you stay clear.
Good batteries are expensive we all know that. But you can get very good batteries for a few $ more like XTAR, WOW, and perhaps the forum liked trustie's flames for the least money.
You can't possibly need more than lets say 4 good batteries at one time. I use 2 but stock another 4 just in case. Well anyone can have different needs however.
Thought this might be the case... thanks for the heads up guys. Sorry, somehow I only saw the information at the top of the page (didn't see specs and pics below).