Depth of Discharge

Depth of discharge (DoD) is the share of a battery's capacity that has been used, as a percentage. It is the opposite of state of charge: a battery at 30% charge has a 70% depth of discharge.

Depth of discharge sets usable capacity. The battery runtime calculator uses 50% for lead acid, so a 100 Ah, 12 volt battery gives 600 of its 1,200 Wh and runs a 100 watt load for 6 hours.

Shallower cycles last longer. Battery University estimates an NMC lithium cell gets about 300 cycles at 100% DoD and about 1,000 cycles at 40% DoD. See the FAQ on how long a 100Ah battery lasts.