EV Powertrain & Battery Management Systems (BMS)

• Lithium iron phosphate (LFP) vs Nickel Manganese Cobalt (NMC) trade-offs
• Series-parallel cell sizing, busbar design, and packaging constraints
• Thermal runaway mechanics, propagation prevention, and liquid cooling plates

• Passive vs Active cell voltage balancing topologies
• State of Charge (SoC) and State of Health (SoH) calculation using Extended Kalman Filters
• Over-voltage, under-voltage, over-current, and isolation resistance fault protection

• Silicon Carbide (SiC) vs IGBT traction inverter thermodynamics and Space Vector PWM
• Field-Oriented Control (FOC) of Permanent Magnet Synchronous Motors (PMSM)
• CCS2 / Type-2 charging communication protocols, PLC controllers, and ISO 15118 standards

Q1: What is the fundamental difference between Passive and Active Cell Balancing in a BMS?

Passive balancing burns off excess energy from higher-voltage cells as heat through bleed resistors until all cells match the lowest cell. Active balancing uses capacitive or inductive charge-shuttling circuits to transfer energy from higher-voltage cells to lower-voltage cells, conserving pack energy, generating less thermal heat, and maximizing total vehicle range.

Q2: Why is LFP chemistry preferred for electric two-wheelers and buses in Indian tropical climates?

LFP (Lithium Iron Phosphate) has superior thermal stability with a thermal runaway threshold around ~270°C (compared to ~210°C for NMC), exceptional cycle life (3,000+ cycles vs 1,500 for NMC), and uses non-toxic iron and phosphate without volatile cobalt, making it much safer in high ambient Indian temperatures (45°C+).