Auto-Sector Interview Preparation

BEV (Battery Electric Vehicle) runs purely on battery and motor. HEV (Hybrid) combines an IC engine with an electric motor but can't be plugged in. PHEV (Plug-in Hybrid) has a larger battery chargeable externally plus an engine. FCEV (Fuel Cell EV) generates electricity onboard from hydrogen.

During deceleration or braking, the electric motor runs in reverse as a generator, converting the vehicle's kinetic energy back into electrical energy that recharges the battery, instead of wasting it as heat in friction brakes. It improves range and reduces brake wear.

A BMS monitors and controls the battery pack: cell voltages, temperature, current, and state of charge. It performs cell balancing, prevents over-charge/over-discharge, manages thermal limits, ensures safety (cutting off on faults), and maximises battery life and performance.

Li-ion NMC (Nickel-Manganese-Cobalt): high energy density, good range, costlier, more thermal-sensitive. LFP (Lithium Iron Phosphate): safer, longer cycle life, cheaper, lower energy density — popular in India for two/three-wheelers and entry EVs. Solid-state is emerging with higher density and safety.

Thermal runaway is an uncontrolled self-heating chain reaction in a cell — excess heat triggers more heat, risking fire/explosion. Prevention: robust BMS, thermal management (liquid/air cooling), cell spacing and fire barriers, quality cells, fuses, and proper enclosure design.

AC charging uses the vehicle's onboard charger to convert AC to DC for the battery — slower (suited to home/destination charging). DC fast charging delivers DC directly to the battery, bypassing the onboard charger, enabling much faster charging at public stations.

SOC is the present charge level relative to capacity (like a fuel gauge, 0–100%). SOH is the battery's current maximum capacity relative to when it was new — a measure of degradation/aging. A battery at 80% SOH holds 80% of its original capacity.

Permanent Magnet Synchronous Motor (PMSM): high efficiency and power density, common in cars. Induction motor: rugged, no magnets, used by some makers. BLDC (brushless DC): common in two/three-wheelers. Switched reluctance motors are emerging for low cost and magnet-free design.

The inverter converts the battery's DC into AC to drive the traction motor, and controls motor speed and torque by varying frequency and voltage. During regenerative braking it converts the motor's AC output back to DC to charge the battery. It's central to performance and efficiency.

For AC: Type 2 and Bharat AC-001. For DC fast charging: CCS2 (Combined Charging System, common for cars), CHAdeMO (older, less common), and Bharat DC-001 for lower-power applications. Two/three-wheelers often use lighter connectors or battery swapping.

Battery swapping replaces a depleted pack with a charged one at a station in minutes. Pros: near-instant 'refuel', lower upfront vehicle cost (battery-as-a-service), centralised charging. Cons: needs standardisation, large battery inventory, and infrastructure investment. Popular for Indian two/three-wheelers.

Cold reduces lithium-ion reaction efficiency and increases internal resistance, lowering usable capacity. Energy is also diverted to cabin heating (no waste engine heat) and battery warming. Range can drop 20–40% in severe cold.

Cells in a pack age and charge slightly differently. Balancing equalises their charge levels so no cell is over- or under-charged, which maximises usable capacity, prevents premature failure, and ensures safety. Passive balancing bleeds excess charge; active balancing redistributes it.

kWh (kilowatt-hour) is the battery's energy capacity. Range ≈ capacity ÷ consumption rate. If a vehicle consumes ~0.15 kWh/km, a 30 kWh battery gives roughly 200 km. Actual range varies with driving style, terrain, load, climate, and speed.

EV packs run hundreds of volts DC — lethal. Technicians must be HV-certified, use insulated tools and PPE (Class 0 gloves), de-energise and verify zero voltage, follow lock-out/tag-out, never work alone on live HV, and handle damaged batteries as fire hazards.

kW (kilowatt) is power — the rate of energy flow (e.g. a 50 kW charger or a 100 kW motor). kWh (kilowatt-hour) is energy — the total stored or consumed (battery capacity). Power tells you how fast; energy tells you how much.

The OBC is the EV component that converts incoming AC (from a home socket or AC charge point) into DC to charge the battery, managing voltage and current safely. Its power rating (e.g. 3.3 kW, 7.2 kW) determines AC charging speed.

An EV powertrain has far fewer moving parts: battery → inverter → electric motor → reduction gear → wheels, with instant torque and no multi-speed gearbox typically. An ICE powertrain needs an engine, multi-ratio transmission, clutch/torque converter, fuel and exhaust systems, and complex cooling.

FAME (Faster Adoption and Manufacturing of Electric Vehicles) is a government subsidy scheme promoting EV adoption and local manufacturing through demand incentives, charging infrastructure support, and localisation requirements. It has significantly driven India's electric two/three-wheeler and bus growth.

Depth of discharge (frequent deep cycling shortens life), high temperatures, frequent DC fast charging, charging to 100% or sitting at very low SOC for long periods, and high charge/discharge currents. Keeping SOC between ~20–80% and good thermal management prolongs life.