What Is Power and power density?
Power
Battery power refers to the energy output of a battery per unit time under a certain discharge regime, measured in W or kW.
Theoretically, battery power can be expressed as
Where t is the discharge time;
C₀ is the theoretical capacity of the battery;
I is the constant discharge current.
At this point, the actual power of the battery should be
In the formula, I^2R_w represents the power consumed by the battery's internal resistance; this power is useless to the load.
Power Density
The power output per unit mass or unit volume of a battery is called power density, also known as specific power, and is measured in W/kg or W/L. Specific power characterizes the operating current a battery can withstand; a high specific power indicates that it can withstand high-current discharge. Specific power is an important indicator for evaluating whether a battery and battery pack meet the acceleration and hill-climbing capabilities of an electric vehicle.
For electrochemical batteries, power and specific power are closely related to the depth of discharge (DOD). Therefore, when expressing battery power and specific power, the depth of discharge should also be specified.
