where can I get Nitecore flashlight? Last time still hv ppl selling, seems that this brand is not so popular. Why huh?

Dear all,

I wanted to buy Fenix PD31 R5 for my dad. My prob is the battery, I will prefer rechargeable, I tried to read about batteries but really confuse. So can someone point out to me:
1. it's best to use rechargeable 2xCR123 or 1x18650?
2. i read if mishandling of such battery will cause burn/explosion?
3. what's the thing i need to take in consideration when charging battery, ie after full charge must off switch immediately or can leave it there for few hours extra?

I come across battery in ebay such as this
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...T#ht_3026wt_905
is it save to use?

Thanks in advance!

means, if don't have knowledge on batteries better don't mess with it right?