Brent,
All answers above are correct. Just putting the batteries in paralle doubles the capacity, and you see this on many heavy duty pickups with campers. As said above, putting them in series just keeps upping the voltage. Three in series would give you 36 volts and no gain in capacity. I use one battery with 750 CCA and have had it since 96.So unless you plan to run 12 or above compression, I really don't think you need all that capacity to start the motor.
Ron
