Chapter 14

Batteries

Batteries on the market today often advertise what their Cold Cranking Amperage (CCA) rating is. CCA is the maximum amperes that can be continuously removed from a battery for 30 seconds at zero degrees fahrenheit before its voltage drops too low to use. A 750 CCA battery can delivery 750 amperes for 30 seconds at zero degrees fahrenheit. This rating is only useful when rating a battery's ability to start your vehicle. These batteries are generally called Starting Batteries. Most vehicles come equipped with Starting Batteries because Starting Batteries are inexpensive to build.

Another rating for a battery is its Reserve Capacity. Reserve Capacity is the number of minutes a battery can maintain a useful voltage under a 25 ampere discharge rate. The higher reserve rating, the better equipped the battery is to run accessories while the vehicle is off. Reserve Capacity is important in marine applications. Reserve capacity may also be important if you need to run accessories, such as cell phones, radios, power inverters, etc. while the vehicle's engine is shut off. This may be important if you take the vehicle camping and it is your only electric power source. Reserve Capacity is more costly to engineer into a battery so these batteries generally cost more.

Another term to be familiar with is Cycle Life. A cycle is a discharge from full charge to the maximum discharged state and then to fully charged once again. The number of cycles a battery can withstand before it fails is called Cycle Life. Starting Batteries have short cycle lives and it is generally best not to allow them to discharge more than 5%. If you want a battery with a long Cycle Life you must purchase a Deep Cycle battery, which can generally be discharged as much as 80%. Now keep in mind that Starting Batteries can be discharged and then charged again to full capacity, but a true Deep Cycle battery can not only withstand a greater discharge but also can withstand the discharge and recharge procedure many, many more times. It is common to see Deep Cycle batteries in marine applications.

For most drivers, a Starting Battery will do just fine because the battery is being used primarily to start the vehicle. You should consult your vehicle's owner's manual for the correct size battery when purchasing a battery. Most battery retailers can assist you with selecting the correct size Starting Battery, but the sales people are generally less informed when it comes to explaining things like Reserve Capacity or Cycle Life.