Thermal Management for Off-Highway Electric Vehicles

Electrification of construction machinery poses new challenges in thermal management, but they can be solved.

As demand increases for electric and hybrid technology advancements in the North American market, off-highway vehicles are subject to many challenges. These range from vibration and shock impacts on the vehicles, to thermal stress and adverse environmental conditions such as water, ice, humidity, dust, and grime.

Like all power electronics, waste heat in mobile applications must be dissipated to avoid costly malfunctions and shutdowns. The failure to disperse this heat could result in the vehicle needing to be switched off for a period, thereby creating a disruption for the end user. For construction machinery, any amount of downtime is not good for business.

In a recent EV thermal-management partnership, Modine and Bosch Rexroth will collaborate on thermal management for off-highway vehicles. Highlighted components represent Modine EVantage (green), which is a liquid-cooled thermal-management system inside Bosch Rexroth’s eLION portfolio (blue). (Image: Bosch Rexroth AG)

The good news is state-of-the-art component technology continues to be developed to meet the constantly rising power requirements for today’s off-highway electric vehicles. The latest developments in contact cooling and other options including heatsink usage and cold plate solutions for converters can solve the thermal-management challenges.

Contact cooling is the most affordable and convenient way to install high-performing converters that manage thermal stress challenges. Choosing the right cooling system solution starts by looking at the installation. Mounting the converters to any heat-conducting surface is sufficient for standard usage, but sometimes this approach is not an option. A possible solution is if the transducer can be attached in a space with an approximate length and width of 11.75-inches (300 x 300 mm).

There are other benefits that make contact cooling attractive. In addition to an easy installation process and being very cost effective, there are the maintenance-free aspects to consider. However, there are times when this approach is not an option. That’s where using a heatsink might be a viable and helpful option. Heatsinks are especially valuable for their passive cooling and space-saving capabilities, and they also are maintenance-free.

The cold plate with liquid cooling allows for greater flexibility on the location of the transducer if an active cooling circuit is available. (Image: Deutronic)

In cases where there is insufficient surface space available on the application for contact cooling, a heatsink can be used if there is good airflow available. An example would be with a vehicle in motion where the airflow is favorable, the converter should be mounted in a place where the heatsink is cooled by the airstream.

If adding a heatsink is not enough, a cold plate solution with liquid cooling would be the next step. A cold plate offers high flexibility, can be integrated into an existing controlled cooling system, and functions in a wide range of ambient environmental conditions. It also can be applied where a cooling circuit already exists, although there are some higher costs and design efforts required with this solution.

A project Deutronic executed for an industrial street sweeper manufacturer required a relocation. The converters were initially installed on the chassis between the steering axle and first drive axle. Due to the chassis heat capacity, contact cooling was the choice as the converters were mounted directly on the chassis.

Later, after the converters were installed, the manufacturer decided to use that space for other components. The converters had to be moved and installed in a more compact volume between the cab and the body, therefore preventing contact cooling. For this reason, cooling via heatsinks was initially considered in a “floating” manner.

Heatsinks are especially valuable for their passive cooling and space-saving capabilities. (Image: Deutronic)

However, since no fan could provide the necessary air circulation in the installation space, it was ultimately decided to use a cold plate/water cooling solution. With this setup, a “floating” or stacked design could be realized. Since the vehicle already had a cooling circuit installed, the cold plates could be inserted into it.

The clear advantage with cold plates is that environmental conditions related to heat have minimal if any influence, provided that the heat limits of the cold plate are observed. The cold plate itself allows for greater flexibility on the location of the transducer if an active cooling circuit is available.

Not all DC-DC contact cooling converters are equal. It’s important to consider these key elements when searching for an integrated thermal-management solution. There are integrated converter designs available that account for ambient temperatures, ensure the best possible heat dissipation via the base plate, and provide optimal connection of the power components.

Tobias Wanzke is Head of Department at Deutronic Electronic (Spartanburg, SC). For more information visit here .