According to the required voltage and capacity, it connects all batteries in series or in parallel to form a battery pack. If it falls off, it will affect the capacity of the battery pack or cause the battery pack to be open and unable to charge. The "iron sheet" on the battery is a nickel sheet. According to the required voltage and capacity, all batteries are connected in series or in parallel to form a battery pack. If it falls off, it will affect the capacity of the battery pack or cause the battery pack to be open and unable to charge.