Using my Hyperion Charger..
 

How many amps should I be charging my 2s2p 6400 mah batterys at, and is there a formula for figuring this out?

I also see people mention charging at 1c. Is this a setting on the charger itself?

1c is the packs capacity, 2c would be double the capacity...so in your case you would want to charge @ 6400ma, you would need to program the charger yourself

my hyperion 610net would sets a charge amp of 6.4 amp based of your batt total capacity
so 1c would be 6.4 amps for you
if your power supply will allow it i have no idea what model hyperion you have
or power supply you may have

I have a 30 amp power supply and the hyperion duo..

So if I had a 5000 mah lipo, I would charge @ 5amps for 1c. Thanks you.