Charge cycle
One full discharge and recharge of the battery. Service life is measured in cycles: 300-700 for lead-acid, 3,000-5,000 for LFP lithium.
A charge cycle is one full discharge and recharge of the battery (going from 100% to 0% SOC and back to 100%). Partial discharges count as fractions of a cycle: two discharges to 50% DoD are roughly equivalent to one full cycle. Battery service life is expressed in charge cycles and depends above all on depth of discharge: a conventional SLI withstands ~300 cycles at 80% DoD yet tens of thousands of starting microcycles (<5% DoD); AGM tolerates ~500 deep cycles, GEL ~700 and LFP lithium between 3,000 and 5,000.
Each cycle gradually consumes active material from the plates and lowers the SOH (State of Health). To maximise available cycles: avoid routinely going below 50% discharge in cyclic applications (solar, caravan, marine), recharge promptly after every discharge (prevents sulphation) and use a smart charger with the right profile for the technology. In a Start-Stop car the battery undergoes hundreds of microcycles per day — which is why it requires EFB or AGM, designed for that cycling pattern.