Meaning
Systematic reduction of the maximum allowable power or current of a battery based on its current thermal state. Implementing temperature derating protects the cell from reaching temperatures that would cause permanent chemical damage or trigger a safety event. The limits are defined by the manufacturer to ensure operation remains within the safe window.
Thermal Boundary
Heat generation increases as the square of the current, making rapid cooling difficult at high discharge rates. If the internal temperature approaches a critical threshold, temperature derating scales back the power demand to allow the system to cool. This mechanism is common in electric vehicles during sustained high-speed driving or rapid charging.
Safety Control
Aggressive cutbacks prevent the onset of thermal runaway.
System Longevity
Software in the battery controller uses pre-defined lookup tables to determine the appropriate power level for any given temperature. While temperature derating might temporarily reduce performance, it greatly increases the overall safety and longevity of the battery pack. Slower acceleration or longer charging times are typical experiences when the environment is extremely hot or cold.
Engineers must balance these performance tradeoffs to meet the warranty requirements and the expectations of the customer. The derating curve is a fundamental part of the system integration process for any high-power battery application.
