|7.2. CCA (Cold Cranking Amps)
If the battery is to used in a starting application, Cold Cranking Amps (CCA) is the second most important consideration; otherwise, for non-starting deep cycle applications, please skip this section and go to Section 7.3. Reserve Capacity (RC) or Amp Hour (AH) Capacity. The battery's CCA rating should meet or exceed, your vehicle's OEM cold cranking requirement, for your climate. BCI's definition of CCA is the discharge load measured in amps that a new, fully charged battery, operating at 0° F (-17.8° C), can deliver for 30 seconds and while maintaining the voltage above 7.2 volts. car and Marine Starting batteries are sometimes advertised by their CA (Cranking Performance Amps) measured at 32° F (0° C), MCA (Marine Cranking Amps) measured at 32° F (0° C), or HCA (Hot Cranking Amps) measured at 80° F (26.7° C). These measurements are not the same as CCA. Do not be misled by the higher CA, MCA or HCA ratings. To convert CA or MCA to CCA, multiply the CA or MCA by 0.8. To convert HCA to CCA, multiply HCA by 0.69. The British and International Electrotechnical Commision's definition of CCA are cranking for 180 seconds and down to 8.4 volts at 0° F (-17.8° C) and for 60 seconds and down to 8.4 volts at 0° F, (-17.8° C), respectively.
To start a four cylinder gasoline engine, you will need approximately 600-700 CCA; six cylinder gasoline engine, 700-800 CCA; eight cylinder gasoline engine, 750-850 CCA; three cylinder diesel engine, 600-700 CCA; four cylinder diesel engine, 700-800 CCA; and eight cylinder diesel engine, 800-1200 CCA. Bruce Bowling and Al Grippo have written a very handy Battery Cold-Cranking Amp Estimation calculator which can be found at http://www.bgsoflex.com/cca.html. To convert CCA, a SAE (Society of Automotive Engineers) standard, to an EN (now known as ETN), IEC, DIN or JIS standard, please refer to the Conversion Table at http://www.midtronics.com/manu...l.pdf from Midtronics.
In hot climates, buying car or marine starting batteries with double or triple the cold cranking amps that exceeds your starting requirement is a waste of money because the extra amps will not be used. A starter motor will only demand what it needs to operate. However, in extremely cold climates a higher CCA rating is better, due to increased power required to crank a sluggish engine and the inefficiency of a cold car battery and the demand is greater. As car batteries age, they are also less capable of producing as much CCA as when they were new. According to the BCI (Battery Council International), diesel engines require 220% to 300% more current than their gasoline counterparts and winter starting requires 140% to 170% more current than the summer. These increased requirements are accounted for in the OEM (Original Equipment Manufacturer) CCA recommendation.
7.3. Reserve Capacity (RC) or Amp Hour (AH) Capacity
For car batteries, an equally important consideration to CCA is the Reserve Capacity (RC) or Amp Hour (AH) Capacity ratings because of the effects of increased parasitic (ignition key off) loads while long term parking, power demands during short trips and emergencies. RC is the number of minutes a fully charged battery at 80° F (26.7° C) can be discharged at a constant 25 amps until the voltage falls below 10.5 volts. European and Asian starting and deep cycle batteries are usually rated in Amp Hours (AH). To convert RC to AH (or AH to RC), check the battery manufacturer's specifications. More RC is better in every case. In a hot climate, if your car has a 360 OEM cold cranking amps requirement, then a 400 CCA rated battery with 120 minutes of RC and more electrolyte for cooling would be more desirable than one with 600 CCA with 90 minutes of RC. There is also a relationship between the weight of the battery and the amount of RC (or AH). The heavier the battery, the more lead is has and potentially a longer service life.