DoD (Depth of Discharge)
Depth of discharge: % of capacity consumed. 50% DoD = battery has 50% capacity remaining.
DoD (Depth of Discharge) is the complement of SOC: it indicates what percentage of the nominal capacity has been extracted. A battery that has gone from 100% SOC to 30% SOC has experienced a 70% DoD cycle. The cycle life of any battery strongly depends on the average DoD: a lead-acid SLI lasts around 30,000 microcycles at 5% DoD but only around 300 cycles at 80% DoD. AGM tolerates roughly 500 cycles at 80% DoD; GEL around 700; LFP 3,000-5,000. The rule in cyclic applications (solar, marine, caravan) is to size the bank not to exceed 50% DoD habitually — that triples or quadruples service life compared to deep discharges.
In automotive starting use, DoD per cycle is less than 5% (only 1-3 seconds of high current), which is why a battery can survive hundreds of thousands of starts.