Battery Technology & Energy Storage Flashcards
7 cards from real EVT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Battery Technology & Energy Storage flashcards as text
An EV battery pack is rated at 400V nominal and 75 kWh. Approximately what is the pack's capacity in amp-hours (Ah)?
Answer: 187.5 Ah
Capacity in Ah = energy (Wh) ÷ voltage (V) = 75,000 Wh ÷ 400V = 187.5 Ah.
What property of lithium iron phosphate (LFP) chemistry makes it particularly safe compared to NMC?
Answer: Thermally stable cathode that does not release oxygen during thermal runaway
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.
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?
Answer: Extended Kalman Filter combining voltage, current, and temperature models
Extended Kalman Filters combine coulomb counting, voltage measurements, and temperature-corrected models to provide the most accurate real-time SOC estimation.
What is the purpose of pre-conditioning a lithium-ion EV battery before DC fast charging in cold weather?
Answer: To raise battery temperature to the optimal range, enabling safe high-rate charging and preventing lithium plating
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.
In a series-connected battery pack, what happens to total voltage and capacity compared to individual cells?
Answer: Voltage multiplies; capacity stays the same as one cell
Series connections add individual cell voltages together while total capacity (Ah) remains equal to that of a single cell.
Which sensor input does a BMS use to implement temperature-derated charging limits?
Answer: Thermistors or thermocouples placed within the battery module
BMS systems use thermistors or thermocouples embedded in battery modules to monitor cell temperatures and apply charge/discharge derating when temperatures exceed safe limits.
What is 'power fade' in an EV battery, and how does it differ from capacity fade?
Answer: Power fade is the reduction in peak power output while capacity fade is reduction in total stored energy
Power fade is the loss of peak power (kW) due to increased internal resistance, while capacity fade is the loss of total energy storage (kWh); both occur with aging but through different mechanisms.