Deep Cycle Battery Specifications
Amp-hours (Ah); the current a battery can deliver for 20 hours at a constant discharge rate before the voltage drops to 10.5 volts. Cycle Life; Cycles represent the repeated charging and discharging of a full battery at 27°C / 80°F until the voltage drops to 10.5 volts and the battery fails to hold half its rated capacity.
This ability to cycle repeatedly is what differentiates deep cycle batteries from starting batteries or dual-purpose batteries, which can't withstand more than a few deep discharges beyond what they were designed for before their capacity begins to degrade.
Starting batteries are designed for maximum repeated discharges of 1-3% DoD. Dual-purpose and high cycle batteries are designed for maximum repeated discharges of 17.5 – 30% DoD. Deep Cycle batteries are designed to withstand repeated depths of discharge of up to 50% to 80% DoD, depending upon technology.