EVT EVT Thermal Management & Cooling Systems

Question 1

What is the primary purpose of the Battery Thermal Management System (BTMS) in an electric vehicle?

Accepted Answer

Maintain battery pack temperature within an optimal operating range to maximize life and performance

Answer

The BTMS keeps the battery cells within their optimal temperature window—typically 15–35 °C—to preserve capacity, cycle life, and safe operation.

Question 2

A liquid-cooled battery pack uses ethylene glycol–water (EGW) coolant. What is the MAIN advantage of liquid cooling over air cooling for high-capacity packs?

Accepted Answer

Higher heat transfer coefficient enabling tighter temperature uniformity across cells

Answer

Liquid coolants have far higher thermal conductivity than air, allowing more efficient heat removal and tighter cell-to-cell temperature variation (typically <5 °C delta).

Question 3

Which component in an EV thermal system transfers heat between the refrigerant circuit and the battery coolant loop without mixing the fluids?

Accepted Answer

Chiller (refrigerant-to-coolant heat exchanger)

Answer

The chiller is a refrigerant-to-coolant heat exchanger that cools the glycol-water battery coolant loop by evaporating refrigerant on the other side.

Question 4

During a hot summer day, a technician notes the EV's available charge rate drops significantly. What is the most likely cause?

Accepted Answer

Battery thermal management system limiting charge rate to prevent overheating

Answer

High ambient temperatures cause the BTMS to throttle charge current to keep cell temperatures within safe limits, resulting in reduced charge acceptance.

Question 5

What does a negative temperature coefficient (NTC) thermistor do as its temperature increases?

Accepted Answer

Its resistance decreases

Answer

An NTC thermistor decreases in resistance as temperature rises, and this predictable change is used by the BMS to calculate battery pack temperature.

(EVT) Certified Electric Vehicle Technician Practice Test

(EVT) Certified Electric Vehicle Technician Practice Test

EVT EVT Thermal Management & Cooling Systems