16 Volt Race Car Batteries

by Wayne Scraba
photos by Wayne Scraba
9/15/03

our racecar doesn't run on petrochemicals. It runs on electricity. Ignition systems need battery power to operate. But what type of battery is required? Batteries are rated by capacity. This is the amount of electrical current or amps a battery can supply for a specific amount of time. Older battery ratings revolved around "Ampere Hour" ratings, but the newest rating system is the "CCA" or Cold Cranking Amps system. The CCA determines the battery's capability of delivering current (amps) under cold conditions. This rating will generally range from 250 to 800 amps, but keep in mind that many (if not all) CCA ratings are rather optimistic. To combat the factory rating game, compare the "RC" or Reserve Capacity ratings of the batteries in question. This rating determines how long the ignition and other electrical components can be operated by the battery alone (without the generator functioning). The RC rating is defined as the length of time (minutes) that a fully charged battery can deliver 25 amps of power at eighty degrees F (maintaining 10.5 volts). In other words, the higher the RC, the better the battery.

When you receive a battery from TurboStart, it's usually dry- charged. That means you have to add your own dry charge sulfuric acid. 4.2 quarts of battery grade sulfuric acid is required to activate the battery. Then the battery is activated, one of the red rubber vent plugs must be removed for venting purposes (more in the next photo). During "activation", remove the slotted cell plugs from each cell and fill with acid to 1/4" over the top of the plates. When all of the cells have been filled to this level, let the battery sit for at least two hours to allow the electrolyte to be absorbed by the plates and separators. Be sure to adjust the acid level to no more than 1/4" above the plates.

RC To Ampere Hours

Thanks to MSD, there is a formula which can be used to easily convert the RC rating into the "old" (you can read that as "useful") battery rating number -- ampere hours (Ah:

25 amps X Reserve Capacity (minutes) = AA 60

Using the above formula, if the battery reserve capacity is 30 minutes, the ampere hour capacity is as follows:

25 amps X 30 = 12.5 Ah 60

The above figure simply means that the battery can supply 12.5 amps of power for one hour. MSD advises that ignition operating time decreases as engine RPM increases. The smallest dedicated battery for use on a MSD 6 or 7 series ignition system is a 12 Ah package. Other ignition systems may require more.

There's no question that today's crop of race cars are becoming more electrically sophisticated. Large capacity electric fuel pumps, electric water pumps, electric fans, electric (or "electronic" solenoid) shifters, throttle stops and even small things like shift lights deplete power and Ah from the battery. Because of this, you have to first determine how many amps (Ah) each of the electrical "accessory" components continuously draw from the battery. For example one of the large billet electric fuel pumps can draw 8 Ah or more. Once you've determined each component's Ah draw, add up the total Ah figures. Using the following chart from MSD, you can then determine the total Ah draw of a typical high powered ignition system at a specific engine RPM.