Capacity Calculation for a Marine Starting Battery

I was asked how to determine the battery size (capacity) for a typical engine starting battery. To that end I have come up with some information on how to do just that.

Starting Battery Ratings: Marine Cranking Amps (MCA) or Cold Cranking Amps (CCA). 1 CCA = 1.3 MCA. The ratings are calculated by the same process just at different ambient temperatures.

Minimum Size for Starting Battery: Engine Displacement (in cubic inches) X 2 (Cranking Requirements) X4 (Reserve Capacity) = Required Battery Size (CCA)

I should note that this calculation will give you the minimum size requirement for a starting battery and I sure won’t hurt to increase the size somewhat. I an also a fan of using a deep cycle rated battery as your starting / reserve.