EVT Battery Technology & Energy Storage 3

Question 1

A technician measures the insulation resistance of an EV high-voltage battery pack and gets a reading of 200 kΩ. What does this indicate?

Accepted Answer

The insulation is degraded and the vehicle should not be energized

Answer

EV high-voltage systems typically require insulation resistance above 100 Ω/V (often 500 kΩ or more for 400V systems); 200 kΩ on a 400V pack falls below safe thresholds.

Question 2

What is the primary purpose of cell balancing in a multi-cell battery pack?

Accepted Answer

To ensure all cells reach the same state of charge to maximize usable capacity

Answer

Cell balancing ensures every cell in the pack operates at the same SOC, preventing weak cells from limiting overall pack capacity and extending pack life.

Question 3

Which battery chemistry offers the highest energy density by weight, making it preferred for long-range BEVs?

Accepted Answer

Nickel manganese cobalt (NMC)

Answer

NMC chemistry achieves higher gravimetric energy density than LFP or NiMH, enabling greater range for a given battery weight in long-range BEV applications.

Question 4

During thermal runaway, in what order do the following events typically occur?

Accepted Answer

Heat buildup → venting → cell rupture → fire

Answer

Thermal runaway follows the sequence of heat buildup triggering electrolyte decomposition, followed by gas venting, then mechanical rupture, and finally ignition.

Question 5

What is 'capacity fade' in the context of EV battery aging?

Accepted Answer

A gradual reduction in the total energy a battery can store over its lifetime

Answer

Capacity fade refers to the irreversible reduction in maximum storable energy that accumulates with cycling and calendar aging due to active material loss and electrolyte degradation.

(EVT) Certified Electric Vehicle Technician Practice Test

(EVT) Certified Electric Vehicle Technician Practice Test

EVT Battery Technology & Energy Storage 3