[secant0give]

The C number is the discharge rate. multiply this by the capacity (mAh) and you have the maximum amps you can draw from the pack.

With the motor/prop combination your going to use, You will probably pull about 80-85A at full throttle so if you have a 3000 30C pack that will provide 90A (3000 X 30 / 1000) but you won't be flying it full peg all the time so a 20-30 C pack will do the job nicely it will give you 60A continuous and 90A for a burst of about 10 seconds. believe me that will be heaps !! Remember the higher the C rating the heavier the packs will be and the dearer they will be as well

These are the ones I use in my edge 540 and that flies very nicely on them, with authority. I only use full peg to go vertical. It will hover on about 1/2 throttle.
http://www.hobbyking.com/hobbyking/store...S_Wh_.html

If you wanted to go 5S then you could use these (below) they would be a little lighter would provide the same current but a little less voltage. Slightly less Watts but still plenty of power to fly that machine !!

http://www.hobbyking.com/hobbyking/store..._Pack.html

If you go 2450 mAh then you want to go for a 30-40C

http://www.hobbyking.com/hobbyking/store...ouse_.html

Or if you want to go even lighter then 2200 mah but you will need 30-40C
http://www.hobbyking.com/hobbyking/store...ouse_.html

The compromise is weight verses flight time.
light weight means better 3D performance ie better acceleration nicer stall and easier/faster recovery when bad shit happens............... and it will

Longer flight time means heavier packs but if you need that weight to make it balance correctly then you may as well have it in battery than in ballast.