You don't understand. 2S = 7.4 volts, 3S = 11.1 volts, 4S = 14.8 and so on. If you run your two 2S2P 7.4 volt 8000's in series you will have a 4S 8000 pack. If you want to return what you have now there is a re stocking fee which is explained on our RMA form at the bottom of our warranty page here: http://www.maxamps.com/warranty.php . So in short there is no 11.1 volt 4S pack. It's quite clear you don't understand what your doing or attempting to do. I would suggest you do a bit more research into your conversion before you make any more purchases.

You may find some useful info here as well: http://www.nitrokillers.com/showthread.php?t=1626

Jason