Cabbie you take the total mah this for you would be 20000mah and as said before divide by 1000 therefore for a 1C charge you can use 20amps
That's when you use a para board voltage stays the same and capacity is added together,
Just remember the batteries have to be within 2% of each other's voltage at the start and all have to be the same pack size ie 3s or 6s you can't mix pack sizes