EV Technology Fundamentals Flashcards

An EVSE sends a J1772 control pilot signal with a 40% duty cycle. What maximum current is it advertising?

Answer: 24 A

For duty cycles from 10% to 85%, available current = duty cycle × 0.6, so 40 × 0.6 = 24 A.

What is the main purpose of the proximity detection circuit in a J1772 connector?

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.

The North American Charging Standard (NACS) connector has been standardized by SAE as which document?

Answer: SAE J3400

SAE published the NACS connector as SAE J3400.

How does the CCS1 (Combined Charging System) connector differ from a standard J1772 connector?

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.

Which is a key advantage of lithium iron phosphate (LFP) battery chemistry compared with NMC chemistry?

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.

Why does DC fast-charging power usually drop sharply once a battery passes about 80% state of charge?

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.

What is the main benefit of an 800 V battery architecture compared with a 400 V architecture?

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.