EVT Thermal Management & Cooling Systems Flashcards
6 cards from real EVT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 EVT Thermal Management & Cooling Systems flashcards as text
What is 'thermal runaway' in a lithium-ion battery cell?
Answer: Self-sustaining exothermic reaction where rising temperature accelerates further heat generation, potentially leading to fire
Thermal runaway is a positive feedback loop where heat causes more reactions that produce more heat, often resulting in cell venting, fire, or explosion if not contained.
Which refrigerant is most commonly used in modern EV heat pump and battery cooling systems in the US?
Answer: R-1234yf
R-1234yf (HFO) has a global warming potential (GWP) of <1 compared to R-134a's GWP of 1,430, making it the current industry standard for automotive A/C and heat pump systems.
A heat pump system in an EV can provide cabin heating more efficiently than a resistive heater. What is the typical Coefficient of Performance (COP) advantage?
Answer: Heat pump COP ≈ 2–3 vs. resistive heater COP = 1.0
A heat pump moves heat from outside air or waste sources into the cabin with a COP of 2–3, meaning 2–3 kWh of heat per 1 kWh of electrical input, while a resistive heater is always COP=1.
When inspecting an EV battery cooling plate, a technician finds a greenish-white deposit near a fitting. What does this likely indicate?
Answer: Coolant leak causing corrosion at the fitting
Greenish-white deposits at coolant fittings are a classic sign of glycol coolant leaks reacting with aluminum, indicating a seal or fitting failure requiring immediate repair.
What is the function of the coolant expansion tank (reservoir) in an EV battery thermal management system?
Answer: Stores reserve coolant and accommodates volume changes due to thermal expansion
The expansion tank acts as a buffer to accommodate coolant volume changes as temperature varies, and as a reservoir to maintain system fill level.
A BMS flags a 'cell temperature delta high' fault with a 12 °C spread across the pack. What is the MOST likely root cause?
Answer: Blocked or restricted coolant flow causing uneven cooling of the pack
A large temperature delta across cells typically indicates uneven coolant flow, often from a partial blockage, air pocket, or failing pump causing poor thermal uniformity.