Storage batteries have a limited life and need replacing when that life is over. There are several considerations to selecting the replacement battery.
- Physical size. The new battery must fit the mounting box and brackets of the vehicle. There may be situations where there is more than enough space. However, a replacement battery should never be too large to fit properly and should be fastened securely in place.
- Electrical size. There are two ways of measuring the electrical size of a storage battery.
Cold Power Rating or Cold Cranking Amps
This rating indicates the power for starting at low temperatures. It is the amperes of electricity that can be delivered at 0 degrees F. for 30 seconds while the battery voltage stays above 7.2 volts. A battery should be selected according to the engine size of the vehicle. A small four-cylinder engine requires fewer cold cranking amps than a large eight-cylinder engine.
Reserve Capacity
This new rating indicates the number of minutes that 25 amperes of electricity can be delivered at 80 degrees F. while the battery voltage is above 10.5 volts. Reserve capacity tells you how much time you will have to keep the engine running when the charging system has failed. The load of 25 amperes is similar to the battery drain from ignition, headlights, and normal accessory use. The more minutes of reserve capacity, the greater the margin of safety.
Selecting a replacement battery is not difficult. Carefully match the requirements of the vehicle to the features provided by the batteries considered. Usually it is a process of placing a value on the available features and making a decision.