Understanding battery basics

What basic terms should I know about when understanding batteries?

Battery Basics

A fully charged battery should rest at about 12.6 - 12.8 volts. A weak battery could read in the mid 11-12 volt range. To charge the battery, the alternator must be at a higher potential than the battery. Most alternators will produce about 14.0 - 14.4 volts, which enables the battery to be charged relatively quickly. This output voltage will vary due to many factors, including ambient temperature, engine or alternator speed and the load on the alternator.

Cold Cranking Amps (CCA)

CCA specifies the number of amps that a battery, fully charged, will deliver at 0 degrees Fahrenheit at 30 seconds of discharge and maintain at least 1.2 volts per cell, which equals 7.2 volts for a standard 12 volt battery.

Reserve Capacity

The reserve capacity indicates the time in minutes that a fully charged battery will deliver 25 amps of current and maintain at least 101/2 volts for a 12 volt battery.

Amp Hour Capacity

The amp hour capacity indicates how long the battery can last under a load for a specific amount of time. The number is calculated by multiplying the current in amperes by the time in hours of discharge down to 1.7 volts per cell.

Internal Resistance

The internal resistance specification indicates how fast the battery discharges a specific amount of current and how long it requires to recharge.

Deep Cycle Capacity

The deep cycle capacity of a battery is the ability of the battery to be recharged, or cycled, after being depleted from full charge to 10 volts. Deep cycle life is rated at a five hour rate.