What is the depth of discharge of lithium-ion batteries and how to understand it?

There are two theories about the depth of discharge of lithium batteries. One refers to how much the voltage drops after the battery has been discharged for a period of time, or how much the terminal voltage is (at which point it is generally discharged). The other refers to the battery capacity, which is how much charge has been discharged.

Lithium-ion battery depth of discharge, factors limiting the depth of discharge of lithium-ion batteries. Since the lithium-ion battery is charged, it must be discharged. Theoretically, the discharge process of lithium-ion batteries is balanced. When discharging, attention should be paid to the speed and depth of discharge. The depth of discharge is the ratio of the amount discharged to the nominal capacity, which is the ratio of the amount discharged to the total storage capacity (nominal capacity). The lower the number, the shallower the flow. The depth of discharge of a lithium-ion battery is closely related to the voltage and current, and can be expressed in terms of voltage and expressed in terms of current.

The depth of discharge for lithium-ion batteries is 80%, which means that they are discharged to the remaining 20% of their capacity.

The depth of discharge affects the battery as follows: the deeper the discharge, the simpler and shorter the life of the lithium-ion battery; another aspect is the performance on the flow curve. The deeper the discharge, the more unstable the voltage and current. At the same discharge regime, the lower the voltage value, the deeper the depth of discharge. Smaller currents discharge more completely. The lower the current, the longer the run time and the less the charge at the same voltage. In summary, any topic on the discharge of lithium-ion batteries has to consider the discharge system and, crucially, the current.

The voltage of lithium-ion batteries decreases slowly as the battery is discharged.

For example, when the battery is discharged to maintain 80% of its capacity, but the battery was originally fully charged at 4.2V, it is now measured at 4.1V (here is an example of an estimate for reference only, values will vary for batteries of different quality and performance).

When a lithium-ion battery doses power to any appliance, the internal resistance of the battery increases as the capacity decreases.

When the depth of discharge is greater, the resistance increases and the current is constant, which requires more power from the battery and wastes it in the form of heat.

The otherwise stable discharge curve of lithium-ion batteries can change dramatically when the depth of discharge is greater.

Therefore, limiting the depth of discharge to a relatively flat range will allow customers to have better control of power and a better experience in their applications.

What to look for in discharging a lithium-ion battery. Discharging a lithium-ion battery is really about identifying the factors that affect the discharge of a lithium-ion battery. The important thing is to do the relevant operations when discharging, which will also contribute to a longer lasting battery.

The deeper the lithium ion discharge, the greater the battery loss. The more fully charged a Li-Ion battery is, the greater the battery loss. Li-ion batteries should be in an intermediate state of charge, where battery life is longest.


Post time: Sep-15-2022