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ITGlossary · Batteries
Depth of Discharge (DoD)
The share of a battery's capacity that has been drawn in a discharge, where 100% means fully discharged.
Technical level:Intermediate
If a 100 Ah battery delivers 40 Ah and is then recharged, the depth of discharge was 40%. DoD is the mirror image of SoC: as the battery empties, one goes up and the other goes down.
Depth of discharge has a strong effect on how long a battery lasts. A lead-acid battery completes far more cycles with shallow discharges than with deep ones, while LiFePO4 batteries cope better with deep discharges. In solar systems used every day, this decides how much capacity you need to buy.
A common mistake is sizing the battery bank on 100% of its rated capacity. Design with the depth of discharge recommended by the manufacturer, often around 50% for lead-acid, so that its life is not shortened.
Questions that mention it
All frequently asked questionsWhat does depth of discharge (DOD) mean for batteries?
Depth of discharge shows how much energy has been drawn from the battery relative to its total capacity.
Related terms
- C-rateThe charge or discharge current expressed as a multiple of battery capacity, e.g. 1C for a 100 Ah battery means 100 A.
- Ampere-hour (Ah)The unit of battery capacity, showing how much current a battery can deliver and for how long, e.g. 9 Ah means 0.45 A for 20 hours.
- Cycle LifeThe number of charge and discharge cycles a battery withstands until its capacity falls, usually, to 80% of the original.
- Fast ChargingA charging method that restores battery capacity quickly without damage by controlling current, voltage and temperature.
- State of Charge (SoC)A battery's current charge level as a percentage of its capacity, from 0% (empty) to 100% (fully charged).
- Thermal RunawayAn uncontrolled temperature rise in a battery, where heat speeds up currents or reactions that produce even more heat.