The automotive industry has increasingly focused its attention on making eMobility architectures safe, efficient, and convenient. Since there are considerable pressures to make electric vehicles (EVs) more attractive to consumers, the industry has focused on three particular aspects that would make EVs as convenient as internal combustion engine (ICE) vehicles: range, battery life, and charging speed. Very few EVs on the market are capable of the range of a typical gasoline or diesel vehicle, and while an ICE vehicle can be fully refueled in just a few minutes, it can take considerably longer to charge an EV. A direct current fast charger can take 20–60 minutes to provide only 80% charge. And an EV’s battery pack has a limited lifespan because a lithium-ion battery loses a little of its capacity each time it is charged and discharged.
Since these factors are foremost on consumer’s minds, OEMs seem to have geared their thermal management efforts to help overcome these challenges. One of the keys to getting the best performance out of batteries and charging systems is to keep them at their optimal operating temperatures. Since the current produced by these systems results in a great deal of heat, keeping them cool is the primary consideration. However, effective thermal management involves much more than just keeping batteries and charging systems cool. There are a host of ancillary systems that must be kept at proper operating temperatures such as power inverters, electric motors, and electronic modules. Heating and cooling of the passenger cabin adds even more complexity to an EV’s thermal management needs. While these systems generally require less cooling than the battery, attention still needs to be paid.
Despite the evolving complexity of an EV’s thermal management needs, OEMs have often designed what might be called “static” thermal management systems with off-the-shelf components. These static systems are in many ways not too different from what might be found on a typical ICE vehicle—a pump circulates coolant through the entire system in a simple loop, using a small number of valves.
While existing systems have been used with a certain level of success, they are not without problems. For instance, these static systems have some limitations as to how effective they are at keeping batteries within their optimal operating temperature range. 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 providing less-than-optimal battery performance.