A car battery charge cycle is a full charge and discharge cycle. Most car batteries and deep cycle batteries have a certain number of charge and discharge cycles before they begin to degrade and not hold as much of a charge. Charge cycle, as a function of battery life, pertains more to deep cycle batteries than regular starting, ignition and lighting batteries. Because these batteries don’t normally get fully discharged before being recharged. However, deep cycle batteries are customarily fully discharged before being recharged. Using a voltmeter will tell you how much charge is left in your battery.
For more info, see Car Battery Repair: When to Fix and When to Replace