All GM Ultium EVs To Feature Standard Heat Pump System For Improved Performance, Charging, Efficiency

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Electric vehicles are better than internal combustion engine (ICE) equivalents in many respects, but one challenge they face is providing heat in cold weather. While ICEs are far less efficient than electric motors, they do provide an ample source of waste heat. EVs have long relied on resistance heaters that draw power from the battery to heat the cabin. But there is a better solution, the heat pump which General Motors

GM
is incorporating as part of its Ultium energy recovery system that will be standard on all of its new EVs.

Unlike a resistance heater, a heat pump doesn’t generate heat, it just transfers thermal energy from one place to another. They utilize refrigerants much like an air conditioner as the transfer medium, but they can do both heating and cooling. Essentially, the heat pump gathers thermal energy from a source and redirects it.

There are other EVs on the road already that use heat pumps, but GM seems to have gone further than most. Most heat pump systems are only used to adjust the cabin temperature. GM is doing that, but also managing the temperature of the drive motors, power electronics and battery.

An example of how GM is using the heat pump is for the “watts to freedom (WTF)” mode that enables maximum acceleration on the new Hummer EV. In order to extract maximum power from electric motors, the magnets need to be cooled down. But the battery may need to be warmed up beyond ambient temperature to get it to the optimum temperature for maximum output. The Ultium motors are oil cooled and that oil flows through an oil-to-refrigerant heat exchanger.

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That refrigerant goes to the heat pump where thermal energy is extracted and transferred to the battery coolant. The result is each component running at its optimal temperature.

Another example is charging. Cold lithium ion batteries have much lower power output and input for charging. Ultium EVs will have a manual control for preconditioning the battery to the temperature that will enable peak charging power as soon as it is plugged in. However, if the driver has selected a DC fast charger as the destination in the navigation system, the vehicle will automatically engage preconditioning as vehicle approaches the charger. In the case of the Hummer that will enable it to ramp up to 350 kW charging rates almost immediately with a suitably powerful charger.

Managing the flow of coolant and refrigerant among all of the devices in the EV is now handled by a single multi-valve controller, similar in function to Tesla’s

TSLA
octovalve unit. The benefit of all this is simpler plumbing, a more compact setup and no additional weight. Because the heat pump and multi-valve system replaces the air conditioning, heating and two discrete cooling systems that were used on the Bolt, it’s also cost neutral.

According to GM the system works well at temperatures down to -22 deg Fahrenheit and the increased efficiency can provide up to 10% more range than a traditional heating and cooling system.

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