As for the current production of lithium batteries, the necessary materials are all made in China, and the quality may be very different. Nowadays, national separators are not very good. Many lithium battery manufacturers import foreign products. Japanese Ube splitters are not bad. I also forgot which company imported copper sheets to South Korea.
Why is China not good at manufacturing 18650 lithium batteries?
Second-hand batteries can only depend on luck. Generally speaking, lithium batteries retain 85-90% of their capacity after 500 empty and full cycles. If it is good, it can be used for 1000 cycles while maintaining 60% power. Before I took it apart, I didn't know how long it had been in use, so I had to take a chance.
Production conditions are limited.
From the point of view of production, the battery voltage of generally imported and domestic 10-cell batteries is relatively close. After fully charging, the test will be accelerated. After testing, import. the battery voltage always conforms to that of household batteries. Most batteries have larger differences, and the appearance of these differences will often quickly shorten the life of the battery, and discharge throughout the production process can easily cause fire hazards. This difference in production could therefore be an important reason why Volkswagen chooses to import lithium-ion batteries.