Cool It Down: Creating a new cooling system for the all-electric E1-X powertrain.
Mercury Racing completed work on the E1-X, a prototype electric outboard for the E1 Series, a new powerboat racing series expected to debut in 2023. Mercury Racing joins the E1 Series as Official Propulsion and Propeller Partner and, as part of that partnership, will contribute to development of the propulsion architecture and propeller for the RaceBird powerboat. This is the fourth and final blog in a series on the partnership.
Electric motors and batteries have one thing in common with internal combustion engines – both create heat and need to be cooled. In the case of the E1-X powertrain, three components require cooling: the electric motor, the inverter located within the outboard motor, and the 35 kWh battery located within the 24-foot (7.3 meter) RaceBird, a foiling powerboat designed specifically for the E1 Series. This requires two separate closed (fresh water) cooling systems and sea water heat exchangers.
To accommodate the required water flow at any engine height or boat elevation over the water, Mercury Racing designed a sea water pickup port located in each strut of the hydrofoil that is attached to the E1-X motor. These pickups feed an electric water pump located in the motor space of the outboard. The system is electric, rather than run off the driveshaft as on an internal combustion outboard, because the motor, inverter and battery need to be cooled when the outboard is not running. For example, after the boat returns to the dock following a race session. Rather than create all-new parts for the cooling system, Mercury Racing engineers looked to existing Mercury components for solutions. The transmission cooler for a Mercury Verado V12 600hp outboard serves as the heat exchanger for cooling the motor and invertor.
“The pressure sensors, temperature sensors, coolant reservoir and other components for the E1-X cooling systems are from Mercury Racing QC4 sterndrive engines,” said Jeff Broman, Mercury Racing Director of Engineering. “This allowed us to develop the E1-X prototype quickly with parts that are on hand and already validated. When the final E1-X design is established and we move to regular production, some of these components may be replaced with newly designed parts optimized for size or weight.”
A second circuit sends sea water to the boat and a cooling system for the battery, with a separate heat exchanger. Rather than traditional engine coolant, the battery is cooled with a non-conducting dielectric fluid designed specifically for thermal management of electrical systems, a more-effective solution than a heat sink or fan cooling.
In testing to date the cooling system developed for the E1-X powertrain has performed well.
As the E1 Team continues to test and exhibit the RaceBird, Mercury Racing will provide updates in future blogs, social media channels and the Community Forum.