Energy storage knowledge

Exploring the jump starter with 4 small batteries can output 200A large current!


In addition to charging the mobile phone, the jump starter can also be used for emergency rescue when the car battery loses power. The output of large current of more than 12V/200A is used for vehicle ignition. So, how does the jump starter produces a large current of 200A? In search of this answer, we disassembled the jump starter for a car that can start with a displacement below 1.3.


The whole body of the jump starter is made of plastic. At the top of the device, there is a Type-C power input interface, USB-A power output interface, and an 8-word DC automotive power output interface. Considering the particularity of the jump starter application scenario, the manufacturer also designed a high-brightness LED lamp between the Type-C and USB-A interfaces to provide convenience for night operation.

the jump starter battery

Internal structure

The jump starter has only a circuit board similar to a charging bank and a battery pack. The battery pack is sealed with a layer of blue plastic. The word 14.8V is printed on the packaging. After actual measurement, in the state of full charge and not connected to the load, the peak voltage of the battery pack can reach about 15V, slightly higher than the full voltage of the car battery. In other words, the small battery pack produces a large current of 200A. We unwrap the battery pack. See that the battery pack is 4 rectangular cells connected in series.  The battery pack comes from a Chinese company named JOYSUN. The cell is made of lithium iron phosphate.

the high rate battery cell of jump starter

How do 4 palm-sized batteries produce 200A current?

We found that the battery pack used a high-rate battery cell. Under normal circumstances, the higher the cell ratio, the greater the output current. The ratio of the cell is closely related to the rated capacity of the cell and the level of charging and discharging current. Taking the battery with a capacity of 20AH as an example, when the charging and discharging current is 20A, the ratio of the battery is 1C. When the charging and discharging current is 200A, the ratio of the battery is 10C. Under normal circumstances, the discharge current of the high-rate cell is above 10C, and some even reach 100C or higher. It is precisely because of the high charging and discharging current characteristics of high-rate cell that it has been widely used in power batteries, model aircraft batteries, outdoor power supplies and other fields in recent years. In this disassembled jump starter, its working principle is to raise the battery pack voltage to more than 12V by connecting four batteries in series. Then, the battery pack voltage reaches the level of the working voltage of the car, and improve the output current through the high-rate battery cell, so as to achieve the standard of starting the car.

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