Power battery is the core component of energy storage for new energy vehicles. It has relatively high requirements for working temperature. If the temperature is too high or too low, it will affect its performance and service life. Tests have shown that when the power battery is continuously charged and discharged at a charging speed of 1c for more than 50 times in an environment above 55°C, the battery capacity will be significantly reduced, and the battery life will be shortened accordingly. When the ambient temperature exceeds 60°C, the battery will have the risk of overheating, burning and explosion due to excessive temperature rise. Therefore, controlling the battery temperature so that it can work in a relatively better temperature range is an important part of new energy vehicle battery management.
The power battery of a new energy vehicle contains a large number of battery cells, like the power battery pack of a Tesla electric vehicle, which is composed of more than 7,000 batteries. The battery has internal resistance. When charging and discharging, there is current flowing inside the battery, so it will generate heat and increase the temperature of the battery. With so many batteries, if the heat generated during their work is not managed, and the heat is not released in time, it is likely to cause the battery to run out of thermal control, shorten the battery life, and even cause a combustion accident.
At present, there are four main ways for battery manufacturers to dissipate heat from batteries, namely, natural heat dissipation, air-cooled heat dissipation, liquid-cooled heat dissipation, and refrigeration heat dissipation.
Natural heat dissipation is to install a heat dissipation device made of high thermal conductivity material on a power battery pack to take away the heat generated during battery operation and dissipate it into the air. This heat dissipation method has the lowest cost, but the heat dissipation effect is not good, and the risk of battery damage is greater. Battery manufacturers generally do not use it on power batteries.
Air-cooling heat dissipation means adding a fan with a heat sink on the basis of natural heat dissipation. The heat sink can increase the heat dissipation area, and the fan can speed up air circulation and discharge the heat generated by the battery work as soon as possible. Air-cooled heat dissipation is similar to that of a computer cpu.
Liquid cooling heat dissipation means adding a set of liquid cooling heat dissipation device inside the power battery pack and forming a loop. After the heat generated by the battery is transferred to the liquid in the radiator, the liquid will generate convection due to the heat transfer, and the liquid will flow on its own in the circuit to take the heat away. Its principle is very close to the way the engine is cooled.
Refrigeration and heat dissipation use refrigerant and the process of gas-liquid change as the heat exchange medium to make the temperature of the power battery drop rapidly. It is equivalent to letting the battery work in an air-conditioned room. It is cold, but the effect is the best and the cost is the highest.
Among the four heat dissipation methods, battery manufacturers and car companies currently choose air-cooled and liquid-cooled heat dissipation. For electric vehicles, due to the huge battery pack and many batteries inside, more liquid-cooled heat dissipation options are selected.
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