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There are many types of lithium ion batteries. According to their shapes, it can be divided into: cylindrical and square type; according to different electrolytes, it can be divided into lithium ion batteries and lithium polymer batteries. At present, most of the batteries for mobile phones are 18650 Cell ( 18 mm diameter, 65 mm long) and square lithium polymer battery core.

The following is an analysis of the safety issues of batteries.

1.18650 cylindrical lithium ion battery

There is a replied safety device in the core of the battery to prevent overheating and overcurrent. In the battery pack, because the temperature of the battery pack is too high or the current is too large, the charge in the battery pack has a high resistance, resulting in the charging and discharge current of the battery pack is cut off, resulting in the fire and explosion.

2. square lithium

MHP-TA and PPTC are close to the battery pack, which can better detect the temperature of the battery, and can show high resistance under abnormal situations, prevent the charging and discharge of the battery, and ensure the safe operation of the battery.

The protective circuit can be composed of two parts:

Protection of active components (PTC, Fuse), also known as first -level protection, passive component protection, is also called second -level protection. The first protection circuit was to prevent overcharge, overload, overloading, and short circuit. ICs used IC to detect the battery voltage and charging current to control the connection and disconnection of MOSFET.