Proportional Valves May be the Key to Improving EV Battery Pack Thermal Management

July 10, 2024

There are considerable pressures to make EVs more attractive to consumers. Consequently, the industry is working hard to improve those aspects of EVs that might help to make them as convenient as internal combustion engine (ICE) vehicles, such as range, battery longevity, and charging speed. Effective battery pack thermal management is crucial to achieving these improvements. While EVs employ sophisticated battery management systems (BMS) that, among other things, keep the battery pack within the proper operating temperature band, there is still one Achilles’ heel.

TLX Coolant Flow Comparison

Most EV thermal management systems simply circulate coolant through the battery pack in fundamentally the same manner that coolant is circulated through the engine block in an ICE vehicle. Cold coolant enters the engine block at one point, absorbs excess heat as it circulates, exits the engine block, and passes through the radiator, where the heat is dissipated. This is perfectly effective for a gasoline or diesel engine, but it is not necessarily ideal for an EV battery pack. Here’s why.

As coolant enters the battery pack and begins circulating, the coolant itself is very cool and able to draw excess heat effectively. But as that coolant makes its way to the downstream portions of the battery pack, it is often too hot to provide effective cooling to the remaining battery cells. The cells that receive less effective cooling tend to degrade more rapidly, shortening the life of the battery pack and hindering battery performance.

The issue of coolant being too hot by the time it reaches the downstream portion of the battery pack may be mirrored in colder temperatures. If hot coolant is used to keep the battery warm, the hot coolant entering the battery pack at one end may lose some heat as it flows through the pack, resulting in uneven heating of the cells with the same detrimental results.

OEMs may wish to consider a more highly engineered approach to routing coolant through the battery pack. A multiport proportional valve that directs targeted coolant flow to different sectors of the battery pack as needed might be the best solution. This could more effectively keep the battery pack within its optimal temperature band across all its cells, improving longevity and performance.

Proportional valves that take advantage of latching technology will also be important for keeping thermal management systems as energy efficient as possible. Latching actuators do not require constant power to maintain a commanded position and need only a short pulse of power to change state. This yields a significant energy savings over valves that need constant power to hold position. Valves using this technology can also be equipped with a fail-safe circuit that returns the valve to a designated safe position in the event that the power supplying these valves is lost.

Improving the thermal management of the battery pack is an ongoing challenge for OEMs. Taking a more targeted approach to circulating coolant through the battery pack may improve its longevity and performance by helping to ensure that all of the cells receive the most effective cooling or heating.

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