EVITP EV Technology Fundamentals 4 — Questions and Answers
Question 1: An EVSE sends a J1772 control pilot signal with a 40% duty cycle. What maximum current is it advertising?
- 16 A
- 24 A (Correct answer)
- 32 A
- 40 A
Correct answer: 24 A
For duty cycles from 10% to 85%, available current = duty cycle × 0.6, so 40 × 0.6 = 24 A.
Question 2: What is the main purpose of the proximity detection circuit in a J1772 connector?
- To measure battery temperature
- To detect that the connector is inserted and help prevent driving away while plugged in (Correct answer)
- To communicate the maximum available current
- To provide the equipment grounding path
Correct answer: To detect that the connector is inserted and help prevent driving away while plugged in
The proximity pin tells the vehicle a connector is present and lets it detect the latch release, which inhibits drive-away.
Question 3: The North American Charging Standard (NACS) connector has been standardized by SAE as which document?
- SAE J1772
- SAE J2954
- SAE J3400 (Correct answer)
- SAE J3068
Correct answer: SAE J3400
SAE published the NACS connector as SAE J3400.
Question 4: How does the CCS1 (Combined Charging System) connector differ from a standard J1772 connector?
- It replaces the pilot pin with a data cable
- It adds two large DC pins below the J1772 layout (Correct answer)
- It uses a completely separate round connector
- It only supports AC charging at higher voltages
Correct answer: It adds two large DC pins below the J1772 layout
CCS1 keeps the J1772 AC inlet and adds two DC power pins below it for fast charging.
Question 5: Which is a key advantage of lithium iron phosphate (LFP) battery chemistry compared with NMC chemistry?
- Higher energy density
- Better thermal stability and longer cycle life (Correct answer)
- Lighter pack weight for the same range
- Better performance in extreme cold
Correct answer: Better thermal stability and longer cycle life
LFP is more thermally stable and lasts more cycles, though it stores less energy per kilogram than NMC.
Question 6: Why does DC fast-charging power usually drop sharply once a battery passes about 80% state of charge?
- The EVSE runs out of available grid capacity
- The BMS reduces current to protect cells as their voltage nears the maximum (Correct answer)
- The connector overheats at high SOC
- Utility demand charges trigger automatic throttling
Correct answer: The BMS reduces current to protect cells as their voltage nears the maximum
The BMS tapers current at high SOC to avoid overvoltage and lithium plating in the cells.
Question 7: What is the main benefit of an 800 V battery architecture compared with a 400 V architecture?
- It removes the need for a BMS
- It delivers the same power at lower current, which allows faster charging with less heat (Correct answer)
- It allows Level 1 charging at higher speeds
- It makes the vehicle compatible only with AC charging
Correct answer: It delivers the same power at lower current, which allows faster charging with less heat
Because P = V × I, doubling voltage halves the current needed for the same power, which reduces resistive losses and cable heating.
