EV Cooling System Description And Function
Description:
The system should manage the ideal temperature levels for all powertrain components, as well as allowing an adjustable, convenient temperature within the passenger compartment.
The aim of the newly developed cooling system is to minimize complexity and promote cross-model and cross module commonality. It consists of two interconnected cooling circuits which are required to meet various requirements with regard to user profile, media and component cooling at any location and in any season.
Cooling System Tasks:
- Ensure optimum temperature level for the HV battery
- Ensure optimum temperature levels for EDS units
- Heating and cooling of interior space
Block Diagram - Overview:
Technical Description:
The temperature of the coolant in engine circuit may range between -40°C and 65°C. The optimum temp for eMotor coolant is 55°C, above 65°C the eMotor goes into a reduced power mode. The maximum pressure in the cooling system is 50 kPa, after which the valve in the lid of the expansion tank opens.
To ensure that the HV battery can always be operated in the ideal operating temperature range of 20°C - 45°C, it is equipped with a complex temperature control system. A separate cooler is installed to control the temperature balance of the HV battery. The battery control unit (BCU) uses a pump and valve system to control the flow of coolant through the HV battery. Information on the thermal state of the battery is provided by the temperature NTCs installed in the battery modules and the temperature sensors in the flow and return line.
For use in BEV vehicles Coolant in the system must be water and glycol 50/50.
Cooling Components:
Battery Cooling Circuit - Overview:
Technical Description - Battery Cooling:
Stationary Vehicle:
When the vehicle is stationary and the outside temperature is below -10°C, the battery pack is heated via the HV heater to ensure that the battery pack remains in the optimum temperature range and prevent it from cooling down too much. The battery pack is cooled during the charging process. Pumps 2 and 3 are capacitively controlled so that sufficient cooling and heating capacity is always available.
Moving Vehicle:
When the vehicle is moving, the battery pack is kept in the optimum temperature range, and any waste heat generated in the process is sent to the interior and/or the cooling package as required.
Electric Motor Cooling Circuit - Overview:
Technical Description - E-Motor Cooling:
Stationary Vehicle:
There is no need to cool the motor when the vehicle is stationary.
Moving Vehicle:
Any waste heat generated by the motors during operation is:
- Used to warm the battery pack
- Used to heat the interior of the vehicle
- Discharged via the cooling package
To ensure that an appropriate flow rate can be achieved, pumps 1 and 4 are connected in series and are also capacitively controlled. Electric pumps 1 and 4 are identical in construction and correspond to pumps 2 and 3. The coolant is distributed in the cooling circuit by the two 3-way valves that are installed.
If the temperature continues to rise, the radiator fan is activated and the radiator shutters can also be opened to draw off the waste heat. However, opening the radiator shutter also leads to a reduction of the residual range, since the air flowing through it has an unfavorable effect on the CW value.