Currently hybrid (HEV) and plug-in hybrid (PHEV) in the commercial mass production and gain more market share, the main obstacle is the battery Laptop Battery. Electric vehicle battery must be used in high-performance, low-cost, long life and high safety performance. Lithium-ion batteries are most likely to meet these challenges. At present, all over the world to do the appropriate research and development to improve the battery characteristics. But even the best battery performance, combined into a poor battery pack battery pack may also lead to overall performance, reduced life, security, deterioration of which led to increased costs. In addition, we also must take into account machinery, packaging, electricity, heat, security, monitoring, control, and other parts of the interface with the vehicle and other issues.
Batteries from the battery pack is generally composed of modules or single cells. A battery module also formed by a number of single cells. Loaded in a battery of electronic and thermal control of the box, this cabinets there is a whole battery system with the vehicle interface to other components of the facilities, and battery management systems. Each module also has its proper packaging, thermal control and mechanical or electronic equipment. This loaded with batteries, thermal control and Sony PCGA-BP2T battery electronic equipment, and other parts of the box is what we usually refer to the battery pack.
Battery Select
The packaging of lithium-ion batteries should take into account the following: battery module interconnection between the single cell design; batteries, battery modules and electronic components, the connection between the specific design; structure subject to shock and vibration protection; how to battery pack for collision protection; select the ideal fixed in position of the vehicle; and vehicles other components of the mechanical interface design. Therefore, in the initial design of battery, it must take into account: safety (abuse of limitations); the entire system of packaging costs; of packaging the life and durability of effects; packaging recyclable and re-use of; manufacturing costs; maintenance / repair of convenience; thermal management (because of temperature influence battery life and performance); electronic monitoring and control; display performance, capacity, recession and so the measurement facilities. Therefore, in the initial selection of a suitable type of battery, battery pack for the packaging Sony PCGA-BP2S battery, interconnect design, thermal management, are very meaningful.
Battery Safety
Security is the largest lithium-ion battery concerns. Abuse trials, over-voltage, over charge, over discharge, overheating, nail puncture, external short circuit, or an internal short-circuit defects and so may lead to thermal runaway and battery electrolyte leakage, smoke damage, openings, fire, or even an explosion. For the application of the battery in the vehicle we should be demanding. Although batteries are by improving the negative electrode materials can improve the safety performance of adding additives and through effective electronic and mechanical control virtually eliminate or significantly reduce the risk of accidents, but are like a pressure and squeeze, as well as thermal runaway caused by internal short-circuit still need special attention. And should therefore be targeted to the battery pack accordingly designed to reduce the impact of these conditions to improve the safety of battery pack.
Small number of large-capacity lithium-ion battery single cell with many small-capacity lithium-ion battery single cell comparative
In the PHEV, HEV and EV on the use of a large Sony PCGA-BP2R battery number of small-capacity lithium-ion battery cell with the use of a small amount of single large-capacity lithium-ion battery single cell is different. For example, Energy CS in the PHEV battery pack for use more than 2000 single small 18650 battery (2Ah). And the Chrysler Corporation in the PHEV battery pack using the 200 a much larger single battery (41Ah). The use of a large number of small-capacity single cells has certain advantages, such as batteries low cost (currently in commodity markets, mostly small-capacity single battery), safety, better (faster cooling), because of the small battery cell while security incidents small size and battery production and processing of higher quality. But there are many drawbacks, including a single cell there are too many inter-connections, requiring higher integration and assembly cost, weight, volume ratio is low, the reliability of difference (integral part of more and somewhat redundant), the need for expensive electrical management . Use fewer large-capacity single cell has some advantages, such as assembly, low cost, weight and volume is high and high reliability (due to the reduced number of connections section). However, the disadvantage is the high cost of batteries, low quality, thermal management becomes more difficult and large-scale security incidents occur. Finally decided to use what kind of Sony PCGA-BP2NY battery trade-off analysis must be based on the specific application.
Cylindrical and prismatic single battery comparison
The use of cylindrical lithium-ion battery single cells and prism (or layers board)-type single cell lithium-ion batteries also have different. Cylindrical single cell can be mass-produced and has a high quality. However, with the battery pack can carry all kinds of vehicles, the shape of the factors of space changing needs, the cost advantage is reduced. Cylindrical design robust and resilient structure, especially the anti-hammer, shock and vibration, can prevent safety accidents. With the cylindrical winding area of single cells become large, its external and internal surface area may be cooling winding layer area ratio is relatively decreased; Therefore, heat transfer and a reduced ability to increase the internal temperature gradient. Prism or layers board design with high external and internal surface area may be cooling stacked around the floor area ratio, easier to carry out thermal management. And the prism-shaped single cell comparable single cylindrical battery provides higher efficiency of the packaging volume. However, if the prism-shaped single cells using a soft-film packaging must also be taken into account in the design to prevent local stress, resistance to hammering, shock and vibration. Corresponding facilities may increase the size and weight, reducing soft packing prismatic single battery size Sony PCGA-BP2NX battery advantage.
Battery Thermal Analysis
Thermal management is a battery in cold environments and high-temperature environments is essential to get a good performance and life. High-temperature lithium-ion batteries to reduce the performance and life expectancy, thus limiting the scope of the vehicle driver (driving range) or performance. Thermal management system of the battery at low temperatures, heating at high temperature to heat the cooling of the battery. The corresponding thermal management cooling and heating system to increase the cost of the battery pack, weight and size. Thermal management is not only in order to maintain the battery temperature is below the maximum limit, but also to maintain the temperature between the single cell uniformity. To improve the battery pack Thermal equilibrium, this change requires a temperature fluctuation in a small area (for example, less than 5 ℃). Therefore, we in the battery pack design, must be based on the thermal characteristics of lithium-ion battery lithium-ion battery type selection and reasonable, and beneficial for the thermal design of the principle of equitable and reasonable battery pack cooling, thermal management system architecture. While ensuring that the system is designed Sony PCGA-BP1N battery with a simple structure, reliable and durable, low-cost and low-power features such as parasitic.
The same kinds of batteries at different temperatures under the conditions of heat consumption rate is relatively
The same battery at different temperatures heat rate (per 1kW h of electricity generated by the consumption of calories) is not the same, this is because the battery's internal chemical reaction and temperature are closely linked. Shown in Figure 3, the ambient temperature on battery performance is very affected. Ambient temperature is lower, battery run-time will be more heat produced by the reaction itself. In the battery within the normal operating temperature, the ambient temperature the higher the battery self-generated heat is relatively less chemical energy consumed by the less efficient. This is because the battery with the surrounding environment, there is heat exchange. Thermal Management should ensure that batteries in their optimum operating temperature range of environments to improve battery efficiency and to ensure that all battery operating temperature of the surrounding environment, consistency in order to ensure that all battery operation status in line.
The same type of battery comparison of different shapes
Layers are generally rectangular battery type, battery is a cylindrical winding type. They are not the same as all manner of packaging, thermal characteristics of different structures exist due to a corresponding difference. Different sizes of cylindrical and rectangular shape of the heat distribution of batteries is not the same. As the cooling surface area of different sizes, the thermal gradients within the battery are also different. Figure 2 rectangular battery W / L big sense that there is a large cooling surface area, the internal temperature Sony laptop battery less heat better performance.
In view of different shapes of cylindrical lithium-ion battery temperature field to be more intuitive, we analyze the same type of different radius, different sizes of cylindrical battery capacity vehicles in the same state, the internal temperature field. Here are two 20Ah batteries in parallel is equivalent to a 40Ah battery.
40Ah battery can be seen within the internal temperature 17 ℃ and 16% of the current density uneven. The two 20Ah batteries in parallel the same capacity battery, only a single cell within the 10 ℃ of temperature and 6% of the current density difference. Large-capacity battery temperature gradient larger, mainly due to the battery cooling surface area caused by a relatively smaller proportion. And experimental analysis of the two 20Ah batteries in parallel drawn more than a 40Ah battery life longer. This explains the application of some of the advantages of small-capacity battery.
Modular approach with different kinds of batteries Comparison
Battery pack is sometimes formed by a number of single cells of the battery modules. The thermal characteristics of single cells vary in their composition of battery modules, due to the number of combinations, as well as the arrangement of battery modules packaged in different ways is also very different thermal characteristics. Therefore, we select the appropriate single battery while also considering forming a modular way, the number of single cells, batteries and packaging methods display arrangement.
We are a group of health heat a smaller force for EV God prismatic lithium-ion batteries Hp PB991A battery liquid ventilation condition in the absence of the temperature field of thermal analysis simulation. Simulation Man-rechargeable batteries in the 1C discharge to the cut-off voltage of constant current state of the battery pack (module) temperature conditions.
The ideal battery pack temperature field distribution shown in Figure 4. Assuming the surface to ensure that each battery heat exchange with the outside world the same boundary conditions.
Battery into the teams actually placed around the different conditions and central cooling. The surface of each battery thermal boundary conditions are different, resulting in an overall temperature difference exists, that produce heat concentrated among high temperature, low temperature edge of the phenomenon (Figure 5).
Composed of a small single cell battery module, the temperature imbalance is relatively small. Composed of modules, the greater the number of single cells, heat the more obvious the phenomenon of concentration. As shown in Figure 6, when a large number of single cells will appear more densely placed in the temperature inhomogeneity, battery pack inside the single cell within the battery module temperature will be greater, there are 45 ℃ great. The small number of single cell battery module composed of densely placed together, the temperature difference is only about 1 ℃.
Such batteries are used in a smaller heat of the small-capacity battery EV, and is smaller in the heat of the vehicle running state did not take a mandatory cooling of the battery module. The actual vehicles in the battery operation of complex, heat increased significantly. For the larger heat applied to PHEV large capacity battery, battery current single large heat rate is higher, Hp PB994A battery resulting from intensive display the temperature imbalances will be more apparent. Module, the temperature difference between the single cell will be increased. Seriously affect the consistency of batteries, but also result in potential safety problems, which makes the overall performance of battery modules greatly reduced. Then on the need for effective thermal management of battery modules to take air-cooled and liquid cooling, if necessary, to take a better performance of phase-change materials as heat transfer medium to carry out thermal management. Therefore, we have selected, after a reasonable single cell type but also the right under the battery characteristics of the modular approach selected, select the appropriate number of single cells, placed in the module package arrangement, as well as methods.
Battery pack should be reasonably designed to play the best battery performance, but also taking into account machinery, packaging, electricity, heat, security, monitor and control many aspects, as well as other parts of the interface with the vehicle and so on. When we select the battery, it should be fully taken into account select the appropriate type, the appropriate modular model, a suitable arrangement of display and packaging options. We can see that the selection of the battery pack and battery performance have an impact, and in severe performance degradation caused battery pack, cost increase, and has potential safety problems and so on. At the same time there is an urgent need for battery manufacturer's concerted efforts to create the optimal storage Hp PB992A battery battery for electric car use.
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