Basic EV Theory

7 Lessons

Electric vehicle architecture, battery management, charging systems, and the future of service.

Overview

Electric vehicles are not coming — they are here. This module covers EV architecture, battery chemistry and management, charging systems (Level 1, 2, and 3), thermal management, and what EV service means for technicians. The vehicles are different, but the diagnostic mindset is the same.

Key Components

  • Lithium-ion battery pack and BMS
  • Drive motor and reduction gear
  • Onboard charger and charge port
  • DC-DC converter
  • Thermal management system

How It Works

An EV uses a large battery pack to store electrical energy, which powers an electric motor through an inverter. The motor drives the wheels through a simple reduction gear (no multi-speed transmission needed). Regenerative braking recovers energy. The Battery Management System (BMS) monitors every cell for voltage, temperature, and state of charge.

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Common Problems

  • Battery degradation reducing range over time
  • Charge port or onboard charger failure
  • Thermal management coolant leaks
  • 12V accessory battery failure
  • High-voltage contactor failures

Diagnostic Tips

  • EV diagnostics are heavily scan-tool dependent
  • Battery State of Health (SOH) is the key metric
  • Check HV battery coolant level and condition
  • Many EV issues are software — check for updates first

Related Systems

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