Where did I go wrong with the battery choices?
Ultrafire 18650s are nothing more than cheap, unreliable, junk. More specifically, they're used laptop batteries that are pulled from old laptops and have an Ultrafire label wrapped around them. So you basically get generic batteries that sometimes work, sometimes don't, sometimes won't hold a charge, sometimes won't charge up at all, sometimes will charge up once or twice before never doing so ever again. It's the gambler's choice. Buy them, roll the dice, and pray for a 7.
"Come on. Daddy needs a new pair of shoes!"
Seriously though they're cheap, unreliable, junk. Not worth buying. But, folks see the low prices and figure they're just as good as the slightly more expensive AW brand 18650s. With flashlights (and batteries) you honestly
do get what you pay for.