How EV chargers work has gotten complicated with all the technical specifications and charging standards flying around. As an electrician who installs these systems throughout the Pacific Northwest, I learned everything there is to know about the actual mechanics of EV charging. Today, I’ll share it all with you.
The Basic Principle
Probably should have led with this section, honestly — EV charging is fundamentally just transferring electrical energy into a battery. The charger manages voltage and current to do this safely. What makes it interesting is how this simple concept gets complicated by safety requirements, efficiency optimization, and battery protection.
AC vs. DC Charging
AC Charging (Level 1 and Level 2)
Your home receives AC (alternating current) power. Your car’s battery needs DC (direct current) power. That’s what makes Level 1 and Level 2 “chargers” technically just power delivery equipment — the actual AC-to-DC conversion happens inside the vehicle using an onboard charger.
This onboard charger limits how fast the car can accept power. Most EVs have 7-11 kW onboard chargers, though some go higher.
DC Fast Charging
DC fast chargers do the AC-to-DC conversion externally in the charging station itself, then deliver DC power directly to the battery. This bypasses the vehicle’s limited onboard charger, allowing much higher power delivery.
The trade-off: DC fast chargers are expensive, require massive electrical infrastructure, and generate substantial heat.
How Charging Sessions Work
When you plug in, the car and charger communicate. The vehicle’s battery management system tells the charger how much power to deliver based on battery temperature, current charge level, and other factors. Charging typically slows above 80% to protect battery longevity.
Smart chargers can also respond to time-of-use electricity rates, scheduling charging for off-peak hours automatically.
Safety Systems
Modern charging includes multiple safety layers — ground fault detection, overcurrent protection, and continuous communication between car and charger. If anything goes wrong, charging stops immediately.
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