Lithium battery terminology, parameters, design and selection details

　　1. Energy density (Wh/L&Wh/kg) :

　　The energy released per unit volume or unit mass of the battery, if it is a unit volume, that is, the volume energy density (Wh/L), in many places directly referred to as the energy density;

　　If it is a unit mass, it is the mass energy density (Wh/kg), which is also called the specific energy in many places.

　　If a lithium battery weighs 300g, has a rated voltage of 3.7V and a capacity of 10Ah, its specific energy is 123Wh/kg.

　　2. Power density (W/L&W/kg) :

　　Divide energy by time to get power, which is measured in W or kW. In the same way, power density refers to the unit mass (some places are also directly called specific power) or the power output per unit volume of the battery, the unit is W/kg or W/L. Specific power is an important index to evaluate whether the battery meets the acceleration performance of electric vehicles.

　　3, specific energy and specific power difference:

　　An example of an image:

　　Higher than the energy of the power battery is like the tortoise in the tortoise and hare race, good endurance, can work for a long time, to ensure that the car mileage is long.

　　The power battery with higher power is like the rabbit in the tortoise and hare race, which is fast and can provide a high instantaneous current to ensure good acceleration performance of the car.

　　4, battery discharge rate (C) :

　　Discharge rate refers to the current value required to release its rated capacity (Q) within a specified time, which is numerically equal to a multiple of the rated capacity of the battery.

　　That is, charge and discharge current (A)/rated capacity (Ah), its unit is generally C(shorthand for c-rate), such as 0.5C, 1C, 5C, etc.

　　For example:

　　For the capacity of 24Ah battery: with 48A discharge, the discharge rate is 2C, on the contrary, 2C discharge, discharge current is 48A, 0.5 hours discharge is completed;

　　Charging with 12A, its charging rate is 0.5C, conversely, 0.5C charging, charging current is 12A, 2 hours charging finished; The charge and discharge ratio of the battery determines how fast we can store a certain amount of energy into the battery, or how fast we can release the energy inside the battery.

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