EV Charging Speed & Onboard Charger Guide: 16A, 32A, 40A, 48A Explained
EV Charging Speed & Onboard Charger Guide
Many EV owners assume that a higher-amp charger always means faster charging. In reality, charging speed depends on both the EV charger and the vehicle’s onboard charger.
This guide explains how charging speed works.
What Is an Onboard Charger?
An onboard charger, often called OBC, is built into your electric vehicle. It converts AC power from your home charger into DC power for the vehicle battery.
The OBC limits how much AC power your vehicle can accept.
For example, if your EV has a 7.2 kW onboard charger, it will not charge faster than about 7.2 kW from AC Level 2 charging, even if connected to a 40A or 48A charger.
Common Level 2 Charging Power
Approximate charging power at 240V:
• 16A: up to 3.8 kW
• 32A: up to 7.7 kW
• 40A: up to 9.6 kW
• 48A: up to 11.5 kW
Actual charging speed may vary based on vehicle efficiency, battery temperature, state of charge, and the vehicle’s onboard charger.
Estimated Range Added Per Hour
Approximate range added per hour:
• 16A: around 11–15 miles per hour
• 32A: around 25–30 miles per hour
• 40A: around 29–38 miles per hour
• 48A: around 35–46 miles per hour
These numbers are estimates. Actual range added depends on the vehicle.
Why a 48A Charger May Not Always Charge Faster
A 48A charger can provide up to 11.5 kW, but your vehicle must be able to accept that power.
Some EVs have onboard chargers around 7.2 kW, while others support around 10.9 kW or 11.5 kW. If your vehicle’s OBC is lower than the charger’s output, the vehicle will only draw what it can accept.
How to Choose Based on OBC
• Plug-in hybrids often work well with 16A charging
• Many EVs with 6.6–7.7 kW OBC work well with 32A charging
• EVs with around 9.6 kW OBC can benefit from 40A charging
• EVs with around 10.9–11.5 kW OBC can benefit most from 48A charging
Final Tip
Before choosing a charger, check your EV’s maximum AC charging rate. This helps you avoid overspending on power your vehicle cannot use.