EVT Battery Technology & Energy Storage 4

Question 1

An EV battery pack is rated at 400V nominal and 75 kWh. Approximately what is the pack's capacity in amp-hours (Ah)?

Accepted Answer

187.5 Ah

Answer

Capacity in Ah = energy (Wh) ÷ voltage (V) = 75,000 Wh ÷ 400V = 187.5 Ah.

Question 2

What property of lithium iron phosphate (LFP) chemistry makes it particularly safe compared to NMC?

Accepted Answer

Thermally stable cathode that does not release oxygen during thermal runaway

Answer

LFP's iron-phosphate cathode is highly thermally stable and does not release oxygen when heated, greatly reducing fire risk during thermal runaway compared to NMC.

Question 3

A vehicle owner reports range anxiety, but diagnostics show the battery SOC algorithm is inaccurate. Which method provides the most accurate real-time SOC estimation?

Accepted Answer

Extended Kalman Filter combining voltage, current, and temperature models

Answer

Extended Kalman Filters combine coulomb counting, voltage measurements, and temperature-corrected models to provide the most accurate real-time SOC estimation.

Question 4

What is the purpose of pre-conditioning a lithium-ion EV battery before DC fast charging in cold weather?

Accepted Answer

To raise battery temperature to the optimal range, enabling safe high-rate charging and preventing lithium plating

Answer

Pre-conditioning heats the battery to its optimal temperature window before fast charging, enabling full charge rate capability while preventing lithium plating that would occur in a cold cell.

Question 5

In a series-connected battery pack, what happens to total voltage and capacity compared to individual cells?

Accepted Answer

Voltage multiplies; capacity stays the same as one cell

Answer

Series connections add individual cell voltages together while total capacity (Ah) remains equal to that of a single cell.

(EVT) Certified Electric Vehicle Technician Practice Test

(EVT) Certified Electric Vehicle Technician Practice Test

EVT Battery Technology & Energy Storage 4