Can You Explain How Battery Depth of Discharge (DOD) Works?

Question:

Hi Jeff great videos on YouTube.  I've got 2 x 210 Ah AGM batteries, you said that you can discharge to 35% and up to 85% I was told you could only use 50% ie down to 50% can you explain how that works. - Mark

Answer:

Hi Mark, with battery life, it's all about compromises. Battery life is measured in number of battery cycles. The deeper the discharge (e.g. 35% of capacity, or 65 DOD) the less the # of battery cycles. Or inversely, shallow discharges (e.g. 70% of capacity or 30 DOD) the more # of battery cycles. Since AGM batteries offer more # of cycles at 50% DOD then flooded LA, you can take advantage of this better battery and go lower on the DOD and sacrifice # of battery cycles. - Jeff