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PACK power battery PACK heat dissipation design scheme method,Power battery PACK heat dissipation is a kind of common phenomenon in design of power battery PACK, only the power battery PACK the cooling effect is good battery performance more safe and stable, all of the power battery PACK have thermal design, accurate to hot principle of a fan or other fall heat power battery PACK, lithium power battery PACK heat PACK solutions are widely used in large-scale energy storage lithium electricity, the electric car battery PACK.
one. What is the heat dissipation of power battery pack?
1,The power battery pack, which contains the primary energy storage capacity of the battery pack as an electric car, is a key component of electric vehicles, which directly affects the performance of electric vehicles. Because of its excellent power output and long life, li-ion power battery is well applied in electric car battery pack. However, the performance of li-ion power cells is sensitive to temperature changes, especially the large capacity and high power li-ion batteries used in vehicles. The load space on the vehicle is limited, the number of batteries is larger and the battery is closely aligned. When the vehicle at high speed, low speed, acceleration, deceleration and alternating runtime under different driving conditions, different discharge the battery will take on a lot of heat generated by the different heating rate, plus time accumulation and space effect will produce non-uniform heat accumulation, resulting in battery operation temperature is complicated.
2,battery, power battery pack fever body dense put, middle area must heat accumulation is more, the edge area is less, increasing the temperature imbalance between various units in the battery pack, intensify the internal resistance and capacity of the battery module, monomer inconsistencies. If accumulated over time, some batteries will overcharge and discharge, which will affect the life and performance of the battery and cause safety hazards. If the electric car battery is not timely ventilation cooling, at high temperatures will lead to the battery pack system, uneven distribution of temperature or temperature will eventually reduce the battery charge and discharge cycle efficiency, effect of battery power and energy, serious when still will lead to thermal runaway, affect the safety and reliability of the battery. Therefore, in order to make the battery pack the best performance and life, we need to optimize the structure of the battery pack, conduct thermal management of it, increase the cooling facilities, and control the temperature environment of the battery.
Two. What are the power pack heat sinks?
1. When the power battery pack heat dissipation adopts the active mode or passive mode, the efficiency will be very different. The cost of the passive system is lower and the measures taken are simpler. The active system structure is relatively complex and requires a larger additional power, but its thermal management is more effective.
2, power battery pack cooling solution also consider cost, quality, space layout, early in mild climates use vehicles are not to use the cooling unit and relying only on air to heat the battery (as shown in figure 1). Some of the hybrid electric cars currently being produced also use ambient air to passive cooling battery packs. Although the air is cooled by air conditioning (ac), it is still considered a passive system.
3. Thermal battery pack heat dissipation according to heat transfer theory, solid and gas, solid and liquid contact generate heat transfer phenomenon. The convection heat transfer coefficient of gas is far less than the convection heat transfer coefficient of liquid, and the liquid and solid contact convection heat transfer capacity is stronger. The greater the heat transfer coefficient is, the more heat transfer will be, the more obvious the heat transfer effect will be, so choose the suitable heat transfer medium. The heat transfer coefficient range of various heat transfer phenomena is shown below.
4. Using liquid as the heat transfer medium, it is necessary to consider electrical conductivity, safety and sealing, as well as the convenience of maintenance in the future, and also take into account the overall weight of the battery pack. The heat storage capacity of phase-change materials (such as liquid paraffin) is strongest and can absorb heat or exothermic heat without temperature rise when reaching phase transition temperature. By selecting the appropriate phase change material, the cell can achieve thermal equilibrium effectively, so as to control the lower limit of the battery temperature and avoid the phenomenon of excessively high temperature. But considering the material's research and development, manufacturing cost and other problems, the most effective and most commonly used still USES air as the heat dissipation medium. At present, the air cooling is mainly used in parallel and serial ventilation, as shown in the figure below. This requires the design of the corresponding air vents in the structure of the lithium battery pack to minimize the air flow resistance and ensure the uniformity of air flow.
5. Power battery pack heat dissipation is generally used to make the air flow from one side of the battery to the other side, thus achieving the effect of removing heat. As a result, the flow of air will flow through the area where the heat is first, resulting in two inconsistencies and a greater temperature difference. In parallel, the air between the modules is straight up. This can effectively distribute air flow to ensure that the battery pack is evenly distributed throughout the pack.
6. When designing the heat dissipation system of power battery pack, the factors should be taken into consideration, which can be seen:
1) the main advantages of using air (air) as the heat transfer medium are: simple structure, light quality, effective ventilation and low cost in the production of harmful gases; The deficiency is: the heat transfer coefficient is low with the battery wall, the cooling rate is slow and the efficiency is low. There are many applications now.
2) the main advantages of using liquid as the heat transfer medium are: the heat transfer coefficient between the 12V portable energy storage battery pack and the battery wall surface is high, and the cooling speed is fast. The deficiency is: the sealing requirement is high, the quality is relatively large, the maintenance and maintenance is complex, need water jacket, heat exchanger and so on parts, the structure is relatively complex.
3) the main advantages of using phase change materials are: high heat transfer coefficient, fast cooling speed, high efficiency, and control of the upper and lower limit of temperature; The downside is that r&d costs are high.
three. Conclusion of heat dissipation design of power battery pack:
1. Power battery pack heat dissipation should select the cooling system according to the thermal characteristics of the battery; Some electric vehicle battery pack, the vehicle often use temperature environment, do not need to heat dissipation can run normally, some vehicles such as pure electric cars need two cooling and heating system to guarantee the normal operation.
2, power battery PACK heat dissipation should also according to the concrete strength requirements to choose what kind of cooling mode, such as PACK lithium batteries in parallel hybrid electric vehicle or some hybrid cars by power assist, air cooling heat dissipation system is enough, for pure electric vehicles and series hybrid electric vehicles, heat is more, may need more effectively liquid cooling system. In addition, the construction of the vehicle should be considered, as well as the reasonable selection of the main passive mode to make full use of the vehicle's own resources.
3. In conclusion, the design of power battery pack heat dissipation system needs to meet the characteristics of simple structure, reliable system, low cost and low parasitic power.
PACK power battery PACK cooling way is usually a variety of flexible use, according to the requirements of the different power battery PACK heat dissipation is different, the corresponding dynamic battery PACK PACK cooling way is also different, view the site map, can learn more relevant power battery PACK heat PACK solution.