Why do Electric Vehicles Need a TMS Thermal
Management System?
Compared with traditional cars, electric vehicles have an additional controller called TMS (Thermal Management System). This controller sounds a bit unfamiliar, but in fact, we have been using a function it contains in traditional cars, which is automatic air conditioning HVAC.
Why does the automatic air conditioning become a thermal management system in electric vehicles? This starts with the vehicle's power system.
1. Differences in power systems
The power system of traditional vehicles comes from the engine. The optimal operating temperature of the engine is 85-105°C. When the temperature is too low, the performance is poor and preheating is required; when the temperature is too high, it will cause damage to the components and require heat dissipation.
Low-temperature preheating of gasoline vehicles usually only requires the engine to start for a while, and the temperature can be raised by its own heat, without additional processing; high-temperature heat dissipation requires turning on the cooling fan to dissipate the engine coolant. In short, the characteristics of the engine are high heat and high temperature, and the temperature control demand is mainly cooling, which is relatively simple.
Therefore, the heat-related systems in traditional cars are mainly air conditioning systems and engine cooling systems. When the air conditioner is heating, it will use the high-temperature waste heat generated by the engine when it is running, but the air conditioner and the engine cooling system are two independent controllers.
The power system of electric vehicles comes from the motor, and the power source comes from the power battery. The characteristics of the motor are similar to those of the engine. It will generate heat when working and needs to be cooled.
However, the power battery is very different. The optimal operating temperature of the power battery is 20-40℃. If the temperature is too low, the battery capacity will drop significantly. The electroplating phenomenon during low-temperature charging will also cause serious damage to the battery.
Excessive temperature will not only accelerate battery aging, but also cause battery expansion, leakage, short circuit, and even explosion. Therefore, compared with the rough traditional engine, the power battery is so precious, and its temperature control must be very precise and meticulous!
2. Integrated thermal management controller ITM
Due to different power systems, the heat-related systems of electric vehicles include air conditioning systems, battery thermal management and motor cooling systems.
From a quantitative point of view, electric vehicles only have one more battery thermal management than traditional fuel vehicles. Is it enough to add one battery thermal management controller?
In fact, the change of electric vehicle power system has led to a closer relationship between the originally independent thermal management systems!
For example, the air conditioning system, the original heating was generated by the engine's waste heat, which is very energy-saving. The heating of electric vehicles can only rely on the heat pump principle or PTC heating principle of the air conditioner.
The heat pump principle requires the compressor to work, and the PTC needs to be powered on for heating. Both methods consume electricity, and PTC consumes more. The electricity comes from the power battery, so the working state of the air conditioning system depends on the performance of the power battery.
As mentioned earlier, the optimal operating temperature range of the power battery is very narrow, and a simple preheating and cooling fan like a traditional car cannot control it. The heating and cooling of the air conditioning system must guarantee the temperature control effect. Therefore, the performance of the power battery depends on the regulation of the air conditioning system.
In the same way, the air conditioner can cool the motor, and the heat of the motor can also be used for the power battery and air conditioning, so the relationship between the three is getting closer.
Too high or too low battery temperature will affect the vehicle's cruising range and air conditioning comfort. The excessive temperature of the motor and electronic control will also affect the driving ability of the whole vehicle. These characteristics put forward higher requirements for thermal management.
The higher requirements of electric vehicles for thermal management and the close relationship between air conditioning, batteries and motors have led to the development of the original independent thermal management towards an integrated thermal management system for the whole vehicle that unifies batteries, motors and passenger compartment air conditioning. This structural integration and functional coupling approach makes it easier to achieve optimal energy consumption and cost for the whole vehicle.
