Right Sizing Your Car Battery

IMG_2482We never think twice about replacing batteries in our electronics, but many hesitate to replace the battery in their vehicle. Car batteries wear out just like any other battery and need to be replaced. There are two measurements of concern when looking for a new battery: cold cranking amps; and, reserve capacity.

Cold Cranking Amps

The power output needed to start a cold engine is called cold cranking amps. The cold Chicagoland weather requires more cold cranking amps than batteries in Orlando or Phoenix. The size of the engine also determines the amount of juice needed to get SUVs started compared to economy cars.

The greatest impact to starting a cold engine is the oil. The amount of power to get the cold sluggish oil moving is much greater than keeping warm oil flowing. The second issue the battery must deal with daily is the chemical reaction within the battery itself. The chemicals that produce the energy are less efficient under cold conditions.

The typical car battery can provide 100% power at 80˚ Fahrenheit, and at 80˚ the car requires 100% of its power to start. However, at freezing a car needs 155% power to compensate for the cold engine, but only has 65% of its power available. Here is a table to clarify the available power against the needed power at various temperatures.

% of Power Available

% of Power Required Temperature









25 350


To compensate for the drop off of power in cold weather when more power is required, the manufacturer provides the number of cold cranking amps provided by the battery to raise the percentage of power available under cold conditions.

The type of car also must be taken into consideration. A diesel vehicle requires more cold cranking amps to start than a gasoline engine. As for gas engines, eight-cylinder engines require more than six-cylinders, and six require more than four.

Reserve Capacity

That brings us to reserve capacity. The measurement is the number of minutes of reserve power it has based on its given load. Directly impacting this number is the parasitic drain. This is the energy drawn from the battery by systems that work when the car is off. Systems include remote start, security, and onboard computers required to maintain its memory.

Reserves are also needed for short distance driving or the short jots that don’t allow the alternator to recharge, or recover the batteries energy used to start the car that day.

Reserves are also reflected in the quality of the battery. Interstate is rated number one in Consumer Reports for car batteries. The quality is very high, lasts at least six years and comes with a 2-year free replacement warranty.

While the Everstart battery is about $10-$15 cheaper and rated for 5 years, it is of a lessor quality that lasts only 2-3 years. The add-on warranty costs about $10 and allows the replacement of the battery for 50% off the retail price. This means you pay 160% for the less expensive battery and replace it once during the 5-6 year period.

Hi-Tech Automotive Specialists only use top rated batteries. We also check the battery of every car that enters our shop to make sure it is correctly sized for the car, its systems and our Chicagoland weather. The volume of work we do on batteries allows us to educate our customers and pass additional savings on through competitive pricing.

© 2016 by Hi-Tech Automotive Specialists, Inc.



About CJ Powers

CJ is an author and speaker.
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