[latexpage]
Teknikimobil.com – After previously discussing the General and THC and Thermal Management sections , we will then discuss the Battery and Powertrain Cooling Heating of the Tesla Model S.
Battery and Powertrain Cooling/Heating (Heating and Cooling)
(c)Tesla
The image above shows the components in the battery and powertrain cooling heating of a Tesla Model S car. It consists of 11 main components, namely:
- Radiator coolant
- Radiator bypass valve
- Battery coolant pump 1
- Coolant chiller
- Coolant heater
- Powertrain coolant pump
- Coolant pipe
- Coolant reservoir
- Series/parallel diverter valve
- Coolant chiller bypass valve
- Battery coolant pump 2
The heating and cooling system includes a radiator, hoses, coolant pump, and valves arranged to provide heating and cooling to the powertrain components and high-voltage battery. The cooler can work in two modes: series mode and parallel mode. Series mode configures the cooling system so that the Battery and powertrain are heated or cooled in series, with heat transfer occurring between the two subsystems. In parallel mode, the battery and powertrain loops run separately from each other and do not transfer too much heat between the two systems.
The dual-function system incorporates a four-way coolant change valve with two inlets and two outlets that can switch coolant routing.
Heating and Cooling Modes
The following modes are available for powertrain heating and cooling requirements. The system automatically applies the mode that best suits the prevailing conditions.
Series Mode – Battery Heating
During cold soak conditions, series mode allows coolant to flow through the motor to the cooling cooler, through the radiator and then flow to the HV battery to warm the battery cells. If additional heating is required, the high voltage coolant heater can be activated to provide additional heat to the coolant just before it enters the battery.
Series Mode – Reduced Cooling Energy
Series mode is also an effective configuration when used at low ambient temperatures. This allows cooling the battery and powertrain using only the radiator, without the need to operate the A/C compressor and cooling system for battery cooling.
Series Mode – High Ambient Powertrain Cooling
In very hot conditions when powertrain radiator cooling is limited, the battery can act as a thermal capacitor to absorb powertrain heat and allow the motor to run cooler. This increases motor efficiency. This only applies until the battery temperature reaches its thermal limit. To extend high temperature operation, a chiller and A/C compressor can be involved to cool the coolant to the battery and then the powertrain components.
Parallel Mode
Parallel mode allows the most efficient use of the radiator for powertrain cooling, as the powertrain cooler can run at much higher temperatures than the battery cooler. This mode also allows the Battery to heat itself gradually so that it does not require active cooling, despite absorbing large amounts of powertrain waste heat.
Also, if the Battery requires cooling but the powertrain does not, the Dell coolant cooling system can be activated just to cool the Battery. During charging, the charger is cooled in the powertrain cooling loop. Operating in parallel mode allows this to happen without adding heat to the Battery.
Series/Parallel Diverter Valve
(c)Tesla
The series/parallel mode valve is a 4-way valve controlled by THC. It contains a position sensor that monitors the THC to compare the desired valve position with the actual. This is used to divert the coolant flow path from going through the Battery and powertrain in series, to divert the coolant flow path into two parallel loops. The Battery Circle consists of the HV battery, DCDC converter, chiller, and coolant heater. The powertrain loop consists of the charger, drive unit, radiator, and coolant reservoir. THC can select two paths for coolant flow through the system.
In series mode, coolant flows through the Battery and powertrain continuously. If the battery temperature is below nominal, heat from the powertrain can be used to passively raise the battery temperature. The main advantage of this strategy is that it does not require additional energy to actively heat the Battery by using a cooling heater. If the battery temperature must be regulated independently, the THC commands the valve to the parallel mode position. In parallel mode, the Battery is isolated from the powertrain cooling loop, and can be actively cooled without being affected by powertrain temperature fluctuations.
Coolant Chiller
(c)Tesla
Consists of two main components, namely:
- Coolant chiller
- TXV
The cooler is a cooler-to-coolant heat exchanger located under the hood and mounted on a bracket with the front sub-frame. The heat sink is used for active cooling of the Battery and DCDC converters. It can also support cooling of drive units (motor, gearbox and inverter) and power electronics.
The heat sink is equipped with TXV at the inlet and outlet ports and is serviced as an assembly.
Coolant Bypass Valves
The thermal management system has two coolant bypass valves: one for the radiator and one for the chiller. The two valves are interchangeable. They are directly controlled by THC, and have position sensors that monitor THC to compare each desired valve position to its actual position.
The radiator bypass valve is installed on the front right outboard corner of the subframe. THC commands the valve to the full radiator position if the system is in parallel mode, or if it is in series mode and both:
- The battery inlet temperature is greater than the active cooling target of the Battery
- The powertrain inlet temperature is greater than the powertrain active cooling target
THC commands the valve to the full bypass position when:
- Battery Heater is commanded
- Battery AND powertrain passive cooling target is 10C greater than intake temperature
The chiller bypass valve is installed on the left side of the subframe, behind the ABS modulator. The THC commands the valve to the full chiller position if there is a request for A/C compressor operation to cool the Battery. Otherwise, the chiller is bypassed. The bypass valve slowly introduces refrigerant to the battery cooling cooler, so that the TXV does not open completely and starve the HVAC evaporator of refrigerant. Such starvation will result in large air temperature variations from the HVAC vents when the chiller is involved.
Coolant Heater
(c) Tesla
Consists of three main components:
- Battery coolant pump 1
- Powertrain coolant pump
- Battery coolant pump 2
The Model S has three coolant pumps: two battery coolant pumps and one powertrain coolant pump.
The two battery cooling pumps are 12V DC brushless centrifugal pumps. Controlled by THC, they pump coolant around the battery to maintain it at optimum temperature.
The powertrain coolant pump is identical to the battery coolant pump. Located at the rear of the cooling reservoir. The powertrain coolant pump is controlled by THC, and pumps coolant around the powertrain components to maintain them at optimum temperatures.
Coolant (Glycol) Temperature Sensor
There are two coolant temperature sensors. One is in-line between the coolant heater and the battery, and provides the Battery inlet coolant temperature to the THC. The other is in-line between the powertrain pump and charger(s), and provides the powertrain injector coolant temperature to the THC. The battery, charger, and drive assembly report internal temperatures to the THC, which then adjusts flow rate, passage, and coolant temperatures to keep those components within their nominal operating range.
Coolant Reservoir Assembly
(c)Tesla
Consists of two main components, namely:
- Coolant reservoir
- Coolant level sensor
The coolant reservoir holds a reserve of 2 liters of coolant and 1 liter for expansion and contraction of the coolant level. It is installed under the hood and contains a coolant level sensor that indicates THC that the coolant level is low. The reservoir is a flow de-gas bottle: most of the coolant flows through the bottle, while a small part of the coolant flow flows into the bottle. The coolant flowing into the bottles passes through a series of settling chambers that allow air to escape from the cooler within a few minutes. Air-free coolant is then drawn from the reservoir. The coolant level should be between the Nominal and Maximum lines when the vehicle is at room temperature.
Coolant
The coolant used is G-48 coolant, supplied pre-mixed with water in the right concentration. G-48 is a long life coolant designed for high aluminum content powertrain systems.
Active Louvers
(c)Tesla
Consists of the following four components:
- Louvered fascia
- Louver actuator
- Louver actuator
- Throat louver
Two sets of grilles are installed on the Model S. The front grilles are visible from the front of the car, and the rear grilles are positioned in the duct between the radiator and condenser. The rear grille is referred to as the throat grille.
The grille is operated by a motor, and the motor is controlled via a Local Interconnect Network (LIN) signal from the Thermal Controller (THC), using feedback from the following:
- Coolant temperature sensors
- Refrigerant temperature sensor
- Refrigerant pressure sensor
- Ambient air temperature sensor
- Vehicle speed sensors
The louvers control the flow of ambient air through the radiator and condenser. This system is designed to maintain the minimum air flow required for cooling. Additionally, minimizing airflow can be used to reduce the time it takes for components to reach normal operating temperatures.
The grille also minimizes the vehicle’s aerodynamic drag when cooling demand is low, reducing vehicle power requirements and increasing range. The grille is closed when the vehicle is turned off, but opens if necessary when cooling the vehicle’s charging system during the charge sequence.
Cold Temperature Operation
Driving: Both sets of grilles are closed to maximize HV heating. Aerodynamic drag is reduced to extend the vehicle’s driving distance.
Charging: Both sets of grids are closed to maximize HV heating.
Normal Temperature Operation
Driving: Throat louvers open if the powertrain or HV Battery needs to reduce temperature. The throat louver also opens if the A/C is turned on, to provide air flow to the condenser). At low speeds, the front grille may also start to open.
Charging: Throat louvers open if the HV Battery needs to reduce temperature.
High Temperature Operation
Driving: Throat louvers open when the powertrain or HV Battery needs to reduce temperature. The front grille also opens when the A/C is turned on or for active HV HV cooling (coolant cooling) during aggressive driving.
Charging: Throat louvers open when the HV battery reduces temperature. The front grille also opens when the A/C is turned on or for active HV cooling (battery cooling) during fast charging.[]