Q&A with Hyperdrive Innovation: review of powertrain cooling
Hyperdrive Innovation Ltd is an R&D business which designs and develops electric and hybrid vehicle drivetrain systems, range extenders and key powertrain components. In this interview, Matthew Beecham talked with Chris Baylis, technical director, Hyperdrive Innovation about cooling challenges for alternative powertrains.
In what ways has the scope of thermal management changed over the past decade?
More accurate and closer control of thermal management is an essential part of maximising the performance of systems as they all have an optimum performance temperature.
As we understand it, there has been a shift in emphasis from the previously predominant direct charge air cooling to indirect charge air cooling assisted by the coolant. What has driven this change and what are the benefits?
The charge air temperature has a huge effect on the output power of an engine. When you compress air in a turbo or supercharger, the air temperature increases significantly so the air density goes down and so does the specific power output. Again, by using coolant systems a more stable result can be achieved across a wide range of ambient conditions. Simply put: the colder the charge air, the greater the power output.
Moving away from the internal combustion engine to the electrified powertrain and lithium-ion batteries, what is the trend there?
Lithium batteries again have an optimum working temperature range and also a safe working temperature range. Hyperdrive has a system that controls the battery temperature as part of the battery management system. For more extreme environments, the battery packs require heating or cooling to keep them in a typical -10°C to +25°C window. Battery manufacturers are continually working to expand this working range.
Which cooling concept will gain acceptance for lithium-ion batteries? Cooling based on refrigerant or coolant or air?
Currently air is our choice for UK and most of Europe but more extreme environments require heating and cooling systems. The challenge is cost, weight and energy consumption.
It is necessary to know the engine in order to cool it. Does the same principle apply to battery cooling?
Yes because different batteries have different amounts of copper, different surface areas being either flat sheet or rolled cylindrical units. So our battery packs are designed and optimized for each type of battery.
I guess increasing electrification of the powertrain is also posing new challenges to cabin comfort. What’s your view?
It is indeed because in today’s all electric vehicles all the power comes from the traction batteries. A cold winter’s day could require 3 to 5 kW of heating in the car so with a 24 kW battery pack giving a working range of around 19kW the HVAC system can consume a significant proportion of the power available. This is in dramatic contrast to internal combustion engines, which expel about 65 percent of their energy as heat. So the EV needs excellent insulation from cold and sun. It needs to be conditioned during charge so the car’s traction batteries are used for traction power and all the systems need to be as efficient as possible. At Hyperdrive, we are working hard to manage these factors so that range can be optimised.