Help with balanced charging: Custom battery pack with IMAX-B6

Batteries and Chargers Rechargeable Batteries
1

I'm going to build a custom light for my bicycle, and today I finished with the battery pack, it consists in a cycling water bottle with 12x18650 inside (4S.3P).

I have installed a XLR connector like this at the end of the bottle:

The external connector is "ground" 0V, and each one of the three internal connectors have 4S batteries (+16.8v when battery full).

I have the IMAX B6, can I charge the three series at once individually? (or may be buying another charger?).

Here is the wiring of batteries, they are TrustFire Protected 18650 "Flames" (all from DX, received at same time, never used, all came with 3.830v):

If it is possible to do it, which JST-XH connector should I buy?

Thanks in advance!

2

This caculator might help.

http://scriptasylum.com/rc_speed/lipo.html

3

Many thanks Komichi!

Now I realize that I have to redo the wiring.

BTW, that page is great! it has lots of great info.