Any idea where I can buy connectors that connect r6b receiver to kk 2.1.5?

http://www.quadkopters.com/product/connectors/male-to-male-servo-lead-jr-10cm-10pcs/

[Admin Note] Unnecessary quote of just prior post removed. Please use "Reply" (or the "Quick Reply" box at the bottom) instead of using "Quote" while responding to the last post in a thread.
Thanks @ashimda, added to the cart.

Quick question, what is the connector to connect xt60(female from lipo) to lipo charger female banana plug?
OK, got xt60 male to dean female, from Satya, quadkopters

That is right connector that you have selected

@Satyagupta thanks for expediting the orders quickly.

I request for a clarification on kk2.1.5 ESC connection!
Should the power and ground pin be removed from ESC bec for M2 to M4? In other words, only M1 should have 3 pin connected, rest only signal pins?

As far as I know for KK2.0 no need to remove any wires from your ESCs. Connect them as it is with signal on the left pin and Gnd. on the right pin. But for Ail, Ele, Thr & Rud pins you can connect the 3 wires to Ail and remove the Gnd & Vcc from the other 3 pins. I mean you can only connect the signal wire to Ele, Thr & Rud pins. I guess this is same for KK2.1.5

Thanks @meet2ami, that's what I read too regarding 2.0 but not finding any documentation on 2.1.5

@jsquadman, you can follow documentation for KK2.0 on KK2.1 too

OK thanks @sooraj

The receiver and ESCs connections for 2.0 and 2.1.5 are same. Here's one link that may help you:

http://forum.flitetest.com/showthread.php?10061-Help-to-connect-wires-to-KK2-1-5

@meet2ami thanks for the link. I will take a look at it and update.

On my 3S lipo, I am seeing 11.69v (measured in lipo charger and volt meter).
Is there something to worry about? Or should I discharge it?

That is nothing to worry about. A fully charged 3S LiPo should reach 12.6V (4.2V per cell) and at nominal voltage 11.1V. You can discharge it lower than that but 11.1V is a good threshold for maximum battery life. Just check your individual cell voltages, they should be with 0.1V of each other.

Thanks @SK1701 I thought at full charge it should be 3.7*3 = 11.1v

If you have not already purchased one, get a lipo alarm and set the alarm to 3.6-3.7V.(3.7 X 3 =11.1V). When you hear the alarm, land the quad and your quad and battery are safe.

@ashimda not bought voltage alarm yet, any recommended from lhs?
Got all the parts but as I was soldering, the iron blew up on me.
Now waiting for another soldering iron to continue the build.

You can use any one of these:
http://hobbysea.com/products.php?258&cPath=10&sid=47661f2df057982556f18d1ec8a3168b
or
http://www.ebay.in/itm/LiPo-Low-Voltage-Alarm-cum-Voltage-Tester-1S-8S-/191461818742?pt=LH_DefaultDomain_203&hash=item2c94038176

I am using them, they are better as they display the voltage as well as triggers alarm when voltage below the thresold you set.

Thanks @meet2ami. Looks like eBay one looks better (from the pics)

I use the same lipo alarm. It does the job.

@jsquadman: Both are same. The one in Hobbysea is with an extra plastic case. Thats it.

Thanks @meet2ami for clarification.

Was able to fly the build, but it is always tilting to one side, need some tuning -- check it out
Maiden flight:

Second flight:

Attached some pics of almost complete quad.