Air Cooling vs Liquid Cooling for OBC
Air cooling vs liquid cooling for onboard chargers: when forced air is enough, when liquid cooling is needed, and what to check for commercial EVs. Read more.
Common Mistakes
- Assuming IP67 means the fan is protected. IP67 applies to the housing. The fan intake and bearings can still be affected by dust, mud, or water spray. Check the fan rating and location separately.
- Mounting an air-cooled unit in a sealed box. The unit will overheat and derate, or fail early. If the location is sealed, you need liquid cooling or a different location.
- Specifying liquid cooling without a loop. A liquid-cooled OBC without a vehicle coolant loop is unusable. Confirm the loop exists, or budget for it, before choosing liquid cooling.
- Checking only peak power. Check continuous power at your highest temperature, for the full charging session. A unit that delivers 6.6 kW for 10 minutes and then derates to 3.3 kW is not a 6.6 kW charger for overnight use.
Related reading: What Is a Bidirectional OBC? V2L, V2V, and V2G Explained · IP67, -40°C, and Automotive Validation Explained · What Drives OBC Development Cost: NRE, Prototypes, Tooling and Validation
FAQ
Is liquid cooling always better than air cooling?
No. Liquid cooling removes heat more effectively, but it adds complexity, cost, and leak risk. For most 1.5-6.6 kW commercial OBCs with a clean air path, forced-air cooling is sufficient and simpler.
Can I convert an air-cooled OBC to liquid cooling?
No, not by adding a cold plate or a fan. Cooling is part of the unit design. If you need liquid cooling, select a liquid-cooled model, such as the Echelon 6.6 kW Bidirectional OBC + 3 kW DC-DC.
What happens if the fan fails on an air-cooled OBC?
Confirm this with the supplier for the specific model. In many designs, the unit derates or shuts down to protect itself. It should not continue at full power with no fan.
Does liquid cooling help in cold weather?
It can help stabilise temperature, but coolant can also freeze or become viscous at -40°C. Ask how the system handles a cold start at -40°C and whether coolant heating is required.
How do I know if my mounting location has enough airflow?
Ask the vehicle thermal team for the airflow and inlet temperature at the mounting location, at the highest expected ambient temperature. If that information is not available, measure it, or use a conservative mounting location with a clear air path.
Related Echelon Products
See the full range on the products page.
Next Step
Send the engineering team your mounting location, available airflow or coolant flow, and highest expected ambient temperature, and request the derating curve for the air-cooled and liquid-cooled options that fit your power and voltage. Choose on continuous power at your temperature, not on the headline rating.
To start, share your vehicle and battery requirements through our contact page, and see how a custom programme is scoped on our OEM/ODM page. Before requesting a quotation, the OBC RFQ checklist lists the inputs that let Echelon quote accurately in one pass.
About Echelon Charger
Echelon Energy Technology specializes in onboard chargers, DC/DC converters, and integrated EV power solutions for commercial and specialty electric vehicles.
For technical discussions, product selection, or OEM/ODM cooperation:
Email: nancy@tici-energy.com
WhatsApp: +86 18114665311
