Electric Car---- Teslas

Cylindrical battery has always been Tesla's only choice, but Tesla's choice of cylindrical battery is also a helpless move in a sense. In fact, the application of cylindrical battery is very extensive. As early as 1992, 18650 cylindrical battery has been widely used in electronic products. 18650 represents the model of the battery, "18" represents the diameter of the battery, "65" represents the height of the battery, "0" represents the cylindrical battery. In the same way, the 21700 battery Tesla uses now is well understood.

The technology maturity of 18650 battery is very high. At the same time, because of its own structural characteristics and standardization, the automation level of cylindrical battery production will be higher. At the same time, foreign Samsung, Panasonic and other major manufacturers can also keep the yield above 98%, and domestic battery manufacturers can basically achieve more than 90%. Therefore, Tesla's choice of 18650 in the initial stage is also the neutralization choice based on the above reasons.

The advantage of the cylindrical battery is that the energy density of the monomer is higher than that of the square hard shell battery. At present, the latest 21700 battery used in Tesla Model 3 has increased the energy density of the monomer to 300wh / kg, which is also the level that other battery forms cannot achieve in a period of time.

At the same time, the cylinder battery cycle performance is superior, can charge and discharge quickly, charging efficiency is high, and output power is larger. In addition, the battery technology is more mature, so the battery consistency is high, and the overall stability of the battery pack is better after pack grouping. In addition, because of the small energy of the cell, it is easier to control in case of failure. Of course, this requires a higher BMS system.

However, the size of the cylindrical battery itself is small, only slightly larger than the number 5 battery we use in our daily life, so the capacity of 18650 battery itself is small. In order to meet the higher power consumption of electric vehicles, it can only be made up by increasing the number. For example, the battery pack of Tesla's earlier models is composed of more than 7000 18650 batteries. A more powerful BMS system is needed to control such a large number of batteries, which is one of the reasons why Tesla is the only one that has long selected cylindrical batteries.

Secondly, the cylindrical battery itself is a cylinder, compared with the square hard shell battery, the space utilization rate is obviously lower than the former. But fortunately, the cooling system can be laid in the gap between the cylindrical batteries, which is a blessing in disguise.

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