I also picked up two of THESE (One for me, one for wife): http://www.ebay.com/itm/131255165693?_t ... EBIDX%3AIT
And one of these to go with the above purchase: http://www.ebay.com/itm/111394555283?_t ... EBIDX%3AIT
Panasonic rules. They really do. I LOVE the 18650 battery. I am trying to have more of them in my life! I'm going to start by upgrading all of the 12V DeWalt Max battery packs from the LAME 1500MAH 18650's to the 3400MAH 18650's. There are 3 of them in this 12V (11.1V really - Well actually 10.8V) and I could more than double the run time.
There is protected and unprotected. 90% of the time you need unprotected batteries as there are already protection circuits in place (In the case of the DeWalt system, the DIY bank and the flashlight)
So you know the breakdown:
18 = 18mm in diameter
65 = 65mm in length
0 = circular in shape
A 16340 is another great cell and is half the size of the 18650 and you can get a 1 cell 16340 flashlight as well
AA sized 3V lithium ions are 14500's - 14mm in diameter 50mm long and round.
Batteries rule this world and these is where I am starting on my next go round of battery fun!!!
Ohh and my unlocked MIFI 2 takes a single 18650.... No wonder it was a 10+ hour run time... http://www.getmifi.com/products/mifi2
P.S, almost ALL the Toughbooks have 18650's in them too and of course they are Sanyo/Panasonic cells!
