Series and parallel connection of 18650 batteries

　　The series parallel combination of 18650 batteries has high requirements for the consistency of the battery itself. If a single battery encounters internal problems, such as low voltage in one of the batteries, it will inevitably lower the voltage value of the entire battery group and increase the internal resistance. If the original current voltage is still used for charging, it is highly likely to cause the battery to heat up and explode, and lithium polymer batteries packaged in aluminum plastic soft packaging also have this situation, However, compared to the 18650 lithium battery packaged in a steel shell, the lithium polymer battery will not explode, but it will inevitably burn. So the battery capacity labeled on the product is not necessarily as large as possible.

　　Moreover, even if it meets the capacity label, how much electricity can actually be provided? In order to provide a more intuitive explanation of this scam, we will talk to our close relative of the emergency starting power supply - the power bank. The capacity of a battery represents the amount of electricity it can provide, just like a pool of water. The larger the pool, the greater the water storage capacity. The process of charging and discharging is similar to the process of storing and discharging water in a pool, and there must be a pressure difference to form water flow. To charge a 3.7V battery, it is definitely not possible to charge it with a voltage of 3.7V, and a higher voltage is necessary. The power banks labeled 10000mAh on the market use 3.7V standard voltage batteries internally. When charging devices with the same built-in 3.7V battery (currently, most devices using lithium batteries have the same 3.7 voltage), they must be boosted to 5V (USB interface standard voltage, except for USB-C). The battery with a "boost board" has a conversion rate of 91% during conversion (which is still a good battery)

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