What is DOD (Depth of Discharge)?

The Depth of Discharge (DOD) is the amount of energy discharged from a battery before it is charged to 100% again. A common way to measure battery cycle life is at 50% DOD. At 50% DOD, the battery has discharged 50% of its energy capacity before it begins charging again.

DOD is the degree of depletion of a battery. If the battery is drained fully, the depth of discharge is 100%. Conversely, if the battery is fully charged, the DOD is 0%. The DOD depends on how much battery power you use every day, which causes your battery to be drained on a daily basis. 

The difference between DOD and SOC

The Depth of Discharge (DOD) and State of Charge (SOC) are both terms of measurement in batteries. SOC is the level of charge of an electric battery relative to its capacity, with units of percentage points (0% = empty; 100% = full). DOD is the inverse of SOC (100% = empty; 0% = full). When DOD is at 100%, SOC is at 0%; when DOD is at 40%, SOC is at 60%. 

SOC is normally used when discussing the current state of a battery in use, while DOD is most often seen when discussing the lifetime of the battery after repeated use.

SOC can be measured using current integration to determine the change in battery capacity over time.

DOD can be calculated as the percentage of battery capacity that has been discharged expressed as a percentage of maximum capacity. A discharge to at least 80% DOD is referred to as a deep discharge.

How Often Should Lithium Batteries Be Discharged?

Unlike other types of batteries that need to be recharged throughout their storage time, lithium batteries do better at 40%-50% DOD (depth of discharge).