Introduction
The on-board charger (OBC) is the heart of your EV's AC charging system. It converts grid AC power into the DC power your battery pack needs. Choosing the right power level directly impacts your daily charging time, installation cost, and long-term convenience. In this guide, we compare the four most common OBC power ratings: 3.3kW, 6.6kW, 11kW, and 22kW.
Understanding OBC Power Levels
An OBC's power rating is determined by its input voltage (single-phase vs. three-phase) and maximum current draw. Higher power means faster charging — but also higher cost, larger size, and stricter electrical infrastructure requirements. Efficiency (η) is equally important: a high-efficiency OBC wastes less energy as heat and charges faster in real-world conditions.
Side-by-Side Comparison
| Spec | 3.3kW | 6.6kW | 11kW | 22kW |
|---|---|---|---|---|
| Typical Use Case | Light EV / DIY storage | Residential EV standard | Three-phase home / light commercial | Commercial / fleet |
| Time to charge 100kWh | ~30 hrs | ~15 hrs | ~9 hrs | ~4.5 hrs |
| Input Voltage | Single-phase 110–240V | Single-phase 110V-240V | Three-phase 400V | Three-phase 400V |
| Size & Weight | Smallest / lightest | Medium | Larger | Largest |
| Cost | Lowest | Mid-range | Higher | Highest |
| Best For | DIY builds, low-speed EV, backup storage | North American home charging | European home / light commercial | Fast AC top-up, commercial vehicles |
Deep Dive: Each Power Level
3.3kW — The Compact Entry Point
The 3.3kW OBC is ideal for low-speed electric vehicles, DIY LiFePO4 energy storage systems, and markets where single-phase 110V is the norm. Its small footprint and low cost make it popular for custom builds and retrofit projects. The trade-off is slow charging — overnight charging is typically required for larger battery packs.
Best for: Golf carts, low-speed EVs, DIY home energy storage, markets with 110V single-phase grids.
➡ Shop Deligreen 1500W OBC for Golf Cart & Low-Speed EV →
6.6kW — The North American Standard
The 6.6kW OBC is the most common choice for passenger EVs in North America. It works with standard 240V Level 2 EVSE (J1772 connector) and can fully charge a typical 60–80kWh battery pack overnight. It strikes the best balance between charging speed, cost, and infrastructure compatibility for most residential users.
Best for: Residential EV charging in North America, passenger car conversions, standard home EVSE setups.
➡ Shop Deligreen 6.6kW OBC | CAN Bus, IP67 Waterproof →
11kW — The European Three-Phase Standard
In Europe, three-phase 400V power is widely available in homes and businesses, making the 11kW OBC the go-to choice. It charges roughly twice as fast as a 6.6kW unit and is compatible with Type 2 EVSE. Installation requires a three-phase electrical connection, which may need an electrician upgrade.
Best for: European residential and light commercial charging, vehicles with three-phase AC charging support.
➡ Shop Deligreen High-Voltage OBC (540V Series) →
22kW — Maximum AC Charging Power
The 22kW OBC delivers the fastest AC charging available. It's primarily used in commercial vehicles, fleet applications, and high-end passenger EVs that support three-phase AC input. Note that not all vehicles support 22kW AC charging — always verify your vehicle's maximum AC acceptance rate before specifying this OBC.
Best for: Commercial vehicles, fleet depots, high-end EVs with 22kW AC charging support, rapid overnight top-up scenarios.
➡ Shop Deligreen Air-Cooled High-Power OBC →
How to Choose the Right OBC
Use this decision framework:
- Grid infrastructure: Single-phase only? Max out at 6.6kW. Three-phase available? Consider 11kW or 22kW.
- Battery pack size: Under 30kWh? 3.3kW is sufficient. Over 60kWh? 6.6kW minimum recommended.
- Use case: DIY/hobby → 3.3kW. Daily driver → 6.6kW or 11kW. Commercial/fleet → 22kW.
- Connector standard: Ensure compatibility with CCS2, GB/T, or Type 2 depending on your market.
- Certifications: For US/EU markets, verify CE, UL, and RoHS compliance.
Deligreen OBC Product Line
Deligreen offers a full range of high-efficiency on-board chargers designed for EV conversions, DIY energy storage, and OEM integration. All models feature wide input voltage ranges, CAN communication support, and are available with CE certification for global markets. US and EU warehouse stock available for fast delivery.
- 1500W OBC — Golf Cart & Low-Speed EV
- 6.6kW OBC — IP67, CAN Bus, Multi-Application
- 3.3kW / High-Voltage OBC (540V Series)
- Air-Cooled OBC — 312V High-Power Series
Frequently Asked Questions
What is the difference between an OBC and an EVSE (charging station)?
The EVSE (charging station or wallbox) supplies AC power and handles safety communication. The OBC, installed inside the vehicle, converts that AC power to DC to charge the battery. Both are required for AC charging.
Can I upgrade my vehicle to a higher-power OBC?
In many DIY and conversion builds, yes — provided your battery BMS, wiring, and thermal management can handle the increased power. Always consult a qualified EV engineer before upgrading.
Can a three-phase OBC work on a single-phase grid?
Most three-phase OBCs will operate on single-phase input but at reduced power (typically one-third of rated output). Check the product datasheet for single-phase derating specifications.
Conclusion
Choosing the right OBC power level comes down to your grid infrastructure, battery size, and use case. For most North American residential users, 6.6kW hits the sweet spot. European users with three-phase access should consider 11kW. Commercial and fleet applications benefit most from 22kW. And for DIY or low-speed EV builds, 3.3kW remains a cost-effective, compact solution.
Have questions about which OBC fits your project? Contact the Deligreen technical team — we're happy to help you spec the right charger for your application.
