The Electric Compressor in BTMS: The "Energy Transport Hub"
of Vehicle Thermal Management
In BTMS, the core role of the electric compressor is to drive the refrigerant cycle, thereby providing the battery system with "active" and powerful temperature control capabilities. It upgrades BTMS from basic "insulation" and "air/liquid cooling" to an "intelligent precision temperature control system" capable of handling extreme conditions.
I. Core Function: Why Does BTMS Need an Electric Compressor?
Batteries generate enormous heat loads under two extreme conditions, far exceeding conventional heat dissipation capabilities:
* High-power DC fast charging: Electrical energy is poured into the battery at extremely high speeds, generating a large amount of heat.
* High-intensity discharge under high-temperature environments, Such as full-load hill climbing in summer or aggressive driving.
At this time, the "passive liquid cooling" of radiators and fans alone is insufficient. A refrigerant cycle must be introduced for active and powerful cooling, and the electric compressor is the power source driving this cycle.
Meanwhile, in winter, the heat pump mode of the electric compressor is the most efficient way to heat the battery.
II. Working Principle: How Does It Serve BTMS? The electric compressor serves the BTMS through two key modes:
Mode 1: Cooling Mode (Powerful Battery Cooling)
This is the most classic and crucial application of the electric compressor in the BTMS.
Compression and Temperature Increase: The electric compressor draws in low-temperature, low-pressure refrigerant gas and compresses it into a high-temperature, high-pressure gas.
Condensation and Heat Release: The high-temperature, high-pressure gas flows through the condenser, where it is forcibly cooled by a fan at the front of the vehicle, condensing into a medium-temperature, high-pressure liquid.
Throttling and Cooling: The liquid refrigerant flows through the expansion valve, causing a rapid drop in pressure and temperature, becoming a low-temperature, low-pressure mist mixture.
Evaporation and Heat Absorption (Crucial Step): The low-temperature refrigerant enters the Chiller. The Chiller is a crucial heat exchanger where the refrigerant evaporates, powerfully and rapidly absorbing a large amount of heat from the battery coolant flowing across the other side of the Chiller.
Heat Transfer Completed: The cooled battery coolant is then pumped back to the battery pack by an electric water pump to cool the battery. The refrigerant, having absorbed heat, turns back into a gas and is drawn back into the electric compressor, completing the cycle.
In simple terms: The electric compressor drives the refrigerant, "stealing" heat from the battery coolant at the chiller, achieving cooling efficiency far exceeding that of air cooling and ordinary liquid cooling.
Mode Two: Heat Pump Heating Mode (Efficient Battery Heating)
This is a key technology for improving winter driving range.
Mode Switching: The refrigerant flow direction is reversed via a four-way reversing valve.
Role Reversal: In this mode, the indoor evaporator becomes the condenser, releasing heat, while the outdoor condenser becomes the evaporator, absorbing heat.
Battery Heating: The system can prioritize heat allocation to the battery pack. The high-temperature, high-pressure refrigerant condenses in a dedicated battery heat exchanger, releasing heat to the battery coolant, thus efficiently preheating the battery.
Energy Efficiency Advantage: The energy efficiency ratio of a heat pump is typically greater than 2.5, meaning that for every unit of electricity consumed, 2.5 units of heat can be transferred, far exceeding the energy efficiency of PTC heating systems that directly use electricity.
