Automotive batteries will frequently have a specification known as cold cranking amps. The specification is often abbreviated to ‘CCA’. Batteries that specify cold cranking amps are generally referred to as starting batteries.
This specification is the measure of a battery’s ability to supply a lot of power for a short period of time.
The specification tells us how much current the lead acid can supply for 30 seconds, at zero degrees Fahrenheit, before the voltage dropping to below 7.2 Volts.
For example, a Battery labeled as being able to provide 300 CCA is a battery that can supply 300 Amps of current for 30 seconds, at zero degrees Fahrenheit, without dropping below 7.2 volts.
Why the Battery Voltage Drops During Starting
As discussed in How A Lead Acid Car Battery Works, a lead acid battery has three major components. They are the negative electrode, the positive electrode and the electrolyte.
The electrolyte moves electrons from one electrode to the other. When an attempt is made to start the vehicle, the electrolyte can not keep pace with the demand. As a result, the voltage drops.
This voltage drop is only temporary and given a short time to rest, the battery voltage will often rebound close to where it started.
How Many Cold Cranking Amps Do I Need?
Your vehicle manufacturer specified how many Cold Cranking Amps you needed when they built the car. For the most part you’re going to match the label or you’re going to get the help of the person at your local auto parts store.
While its acceptable to get a battery that has a little higher rating, purchasing a battery with significantly more will not buy you much.
In fact, needing a more powerful battery to start a vehicle is an indication that you may have other problems.
Among the things you should be looking at are the connections to your battery and vehicle starter. Dirty and loose connections represent a resistance to current flow. Restoring the connections will often alleviate many of your problems.
How does CCA compare to MCA?
MCA stands for Marine Cranking Amps and the specification is very similar to that for Cold Cranking Amps.
Marine Cranking Amps tell us the peak current that a battery can supply for 30 seconds at 32 degrees Fahrenheit as opposed to 0 degrees Farenheit.
This can be a useful specification as batteries tend to perform better in warmer weather.