Deep battery discharge
The depth of discharge of the battery or Depth of Discharge refers to the percentage of discharge of the charge of a battery, which decreases the number of battery charge cycles or the life of the battery in general.
Normally, the capacity of batteries is measured by the value of amperage during one hour, and its unit is ampere per hour (Ah).
By drawing current from the battery, its charge becomes less and less. For example, if we receive a current of 5 amps from a 10 amp battery per hour, after one hour it can be roughly said that 50% of the battery charge has been discharged.
As mentioned above, when a current equivalent to 5 amps is drawn from a 10 amp per hour battery, after one hour, something like 50% of the battery charge is discharged, which is when the discharge process stops.
DOD depth of discharge is equal to 50%.
It should be noted that every battery has a number of authorized charging cycles, which increases the number of times of charging and discharging, its life is reduced, and after reaching the authorized charging cycle, the quality of its work is reduced and it is no longer possible to use its full capacity.
By increasing the number of times the battery is charged and reaching the allowed value, the quality of the current and the capacity of the battery will decrease, in which case you cannot expect high efficiency from the battery. In most cases, the battery can no longer be used and it is said that the life of the battery has ended.
Battery life and the number of allowed charge cycles are included in the battery catalog, but its value is not fixed and is highly dependent on the DOD discharge depth parameter. So that by reducing the DOD, the number of battery charge cycles and consequently its life increases. For example, in a lead-acid battery that is also used in solar power systems, if the depth of discharge is 30%, the battery life is about 3-4 years, and if the depth of discharge reaches 50 or 60%, the battery life Between 2 and 3 years. By increasing this value to 80%, the battery life reaches 6 months, which is very expensive in a solar power system.
The figure below shows the relationship between the life of a battery and its depth of discharge (DOD).
https://bit.ly/2MGJpO4
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This post is written by roza_hj