From the perspective of reliability, we will evaluate the manufacturing reliability of Tesla's 18650 cylindrical battery and the reliability of the fuses connected inside. In essence, Tesla's battery pack does not have the possibility of low cost. This is because the 18650 battery itself is lower in cost, but in order to ensure the cascade connection between small batteries, a lot of safety considerations have to be paid. The connection of so many fuses may be very difficult for mass production. Toyota has great strength in new energy vehicles, but after its electric vehicle plan suffered serious setbacks, there have been few attempts at large-capacity batteries. In essence, its plug-in prius is more biased towards hybrid vehicles.
Summarize a few characteristics of this:
1. The battery pack can be very compact with almost no gaps in the middle.
2. The shock resistance and shock resistance are relatively good, and shock absorption buffer materials can be added between the battery cells.
3. The process of heat dissipation is converted into a heating process, which makes it possible to operate the lithium battery at a low temperature.
4. Ensure the uniformity of the heat dissipation of the battery CELL.
5. The cost is relatively high, mainly in the price of high-pressure pumps and polymer batteries, both of which have a lot of room for price reduction.
6. Safety, the safety of the polymer battery itself is easy to manage.
In this paper of SAE, the author mentioned the simulation method of module cooling Integrated SimulaTIon Process for the Thermal Management of LiIon Batteries in AutomoTIve ApplicaTIons
Overall, this article is somewhat theoretical and there are some problems with the entire design.
In this paper by SAE, the Thermal CharacterizaTIon & Management of PHEV Battery Packs (Compact Power, Inc) of polymer battery thermal evaluation is introduced in more detail.
The structural design of the internal flow channel of the heat sink will also have a certain effect on the distribution of water flow and the efficiency of heat dissipation (heating), which directly affects the various parts of the CELL (this CELL is generally a large cell with several batteries in parallel) Uneven temperature.
Delphi's solution described in the first half (recommended method for liquid cooling of lithium batteries for electric vehicles (above)) is patented. I don't know if it means that such a structure cannot be used (as shown in Figure 1):
Since liquid cooling only removes heat from the inside of the battery pack, more problems need to be solved. GM is currently the most complete about this piece. If you are interested, you can refer to some heat dissipation diagrams of VOLT.
Teacher Wu Yeqing wrote two introductory articles:
"Thermal Design of Electronic Products"
"Thermal Design of Electronic Equipment (Continued)"
The point I want to mention here is that when the industrial system is transplanted into the car, the thermal design of the entire electronic product (including the motor, motor controller, DC / DC high-voltage conversion and charger, the most special is the battery Group) The heat dissipation requirements of these components need to be strictly considered. As has been summarized before, in the case of a hot day, the car not only has to withstand the ambient temperature of the ground as high as 40 degrees or more, but also dissipates the heat in the passenger compartment. These devices on the chassis face a systematic Risks of thermal management.
figure 1
Sometimes I still ca n’t understand how much damage the current Chinese DC charging standard will bring to the electric vehicle bus battery pack. Secondly, I ca n’t understand the 32A special car charger. According to the Chinese voltage, it should be 6.6KW. The manufacturer made a non-liquid-cooled charger; the cruel fact is that in order to meet the requirements of most regions and more demanding, suppliers in South Korea, Japan and the United States all adopt liquid when the charger level is above 2.2KW cool down. This is certainly related to the car's system, the domestic technology is too advanced.
The entire heat dissipation system has more systematic control requirements. Especially for batteries, it needs to have different heat dissipation control algorithms like thermal insulation equipment to ensure that the battery pack is within the appropriate temperature range and that the battery pack is single Temperature uniformity. In the process of analysis, I think it may take a few steps to get a set of design results briefly:
1. Through the working conditions of the whole vehicle, estimate the working conditions of the battery pack that need to be discharged and charged;
2. Use simulation to verify the above conditions;
3. Derivation of the heat production of the battery pack under discharge and charging conditions by estimation;
4. Consider the choice of system (liquid cooling and air cooling); Note: In fact, further subdivision is required, please refer to "HEV Battery Heat Generation and Heat Dissipation Considerations".
5. Consider the heat dissipation conditions required by the single battery with normal values;
6. Under the given heat dissipation conditions (liquid cooling is the inlet water pressure and temperature, air cooling is the power of the fan and the temperature control of the air at the air inlet), design the corresponding heat sink or heat dissipation gap;
7. Simulation results through fluid design software.
Such steps may be too simple. In terms of heat dissipation design of the system, I belong to the category I just touched. I hope to communicate with everyone to improve the design level.
Silicon Transistor are solid-state semiconductor devices with functions such as detection, rectification, amplification, switching, voltage regulation, and signal modulation. The transistor acts as a variable current switch and can control the output current based on the input voltage. Unlike ordinary mechanical switches (such as Relay and switch), transistors use electrical signals to control their opening and closing, and the switching speed can be very fast. The switching speed in the lab can reach more than 100GHz.
Silicon Transistor, Power Transistor, IGBT Transistor, N-Channel Transistor, PNP Transistor
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