Common terminology of Lithium-ion battery (2)

C-rate

C is the first letter of capacity, which is used to indicate the current value when the battery is charged and discharged. For example, when the rated capacity of a rechargeable battery is 1000mah, it means that the discharge time lasts for 1 hour at 1000mA (1C); the discharge time lasts for 5 hours at 200mA (0.2C). The charging can also be calculated according to this.

Cut-off discharge voltage

The cut-off discharge voltage refers to the lowest working voltage that the battery is not suitable for further discharge. Basing on different battery types and different discharge conditions, the requirements of battery capacity and life are also different, so the specified battery cut-off discharge voltage is not the same.

Open circuit voltage (OCV)

When the battery does not discharge, the potential difference between the two electrodes of the battery is called the open circuit voltage. The open circuit voltage of the battery will vary according to the materials of the positive and negative electrodes and the electrolyte of the battery. If the materials of the positive and negative electrodes are identical, the open circuit voltage of the battery will be the same no matter how large the volume of the battery is and how the geometric structure changes.

Working voltage

Working voltage refers to the voltage displayed in the discharge process after the battery is connected to the load, which is also known as discharge voltage. The battery working voltage at the beginning of discharge is called initial voltage. After switching on the load, the working voltage of the battery is lower than the open circuit voltage due to the existence of OHMIC resistance and polarization over potential.

Depth of discharge (DoD)

In the process of using the battery, the percentage of the capacity released by the battery to its rated capacity is called the discharge depth. The discharge depth has a deep relationship with the charging life of the secondary battery. The deeper the discharge depth is, the shorter the charging life is. Therefore, deep discharge should be avoided as far as possible in use.