Understanding batteries

[lovenhim]

 Hello everyone. I am new to the quality flashlight and I am curious about batteries. I know the basics AA, AAA, C, D, and CR123. Then there are these batteries with numbers only and I see where you can use XYZ battery rather than 2 CR123's, etc. I own these lights:

Fenix LD01
Fenix E01
Quark 123 standard
Preon 2
Romisen RC-N3 2
Surefire C2 Centurion

I EDC the Fenix LD01 or the Quark 123 standard or the Preon 2. The Romisen and Surefire are those lights that sit but I want them to be there when needed, too large for EDC. Thanks for the help.
Edit/Delete Message

[jzmtl]

http://www.batteryuniversity.com/

[lovenhim]

Thank you for that link.  Reading time. 

[jzmtl]

Never thought there would be a battery university now did you. 

I don't think the website covers this, but the 5 digit number for battery means the physical size. First two digit is diameter in mm, second two is length, last is shape (0 is cylindrical). All common battery has a name like that just nobody calls them by that.

[Mike, Lord of the Spammers!]

All you need to really understand (at least where AA and AAA are concerned) is the magic that is Eneloops

[nuphoria]

It's all new to me too - when I realised it pertained to size, it started to make more sense!

As a rule when using li-ons, it seems that they are safer as one instead of many... so one 18650 is safer than two RCR123s. They are a little bit prone to blowing up otherwise!

Lots to learn... so little time....  

[lovenhim]

So in a flashlight like a Surefire C2 Centurion if you use recharables in it, then you are better off with one 18650 battery over two RCR123's because it is safer?  OK, this cuts your voltage in half doing this, so what about the brightness of the light?  My model is an incandescent.  In that case would I be better to use two 3.6v RCR123's to have a brighter light? 

[nuphoria]

I think that depends on the voltage of the drop-in... I know there's lots of help on CPF for us newbies on that subject!

Most Surefires seem to have a tube which needs to be bored in order to take 18650 cells I believe, hence the popularity of clone hosts such as the Solarforce L2 etc.

[jzmtl]

So in a flashlight like a Surefire C2 Centurion if you use recharables in it, then you are better off with one 18650 battery over two RCR123's because it is safer?  OK, this cuts your voltage in half doing this, so what about the brightness of the light?  My model is an incandescent.  In that case would I be better to use two 3.6v RCR123's to have a brighter light? 

No you'll blow the bulb, incan bulb can be overdriven a little bit but they are not very tolerant of voltage change. LED voltage range depends on the circuit design, but if you exceed that you can blow the circuit too.

If you want to use rechargeable with incan, look into lumen factory, they make bulb designed for that.