Electric tool

Abstract

The invention provides an electric tool which comprises a battery pack assembly and a control component. The electric tool is characterized in that the battery pack assembly comprises a first battery group and a second battery group with the same voltage, a normally closed first micro switch is arranged between the anodes of the first battery group and the second battery group, and a normally closed second micro switch is arranged between the cathodes of the first battery group and the second battery group. The control component comprises a first terminal, a second terminal, a third terminal and a fourth terminal and also comprises a driving component which allows the first micro switch and the second micro switch to be switched on at the same time. The output end of the control component supplies power to the electric tool with first voltage obtained through the parallel connection of the first battery group and the second battery group or second voltage obtained through the series connection of the first battery group and the second battery group. The electric tool is characterized in that the series and parallel connection of the battery groups are completed by the control component, the circuit size is reduced, the heating rate and failure rate of the circuit are reduced, the battery pack assembly is internally provided with the two normally closed micro switches, two groups of battery ports are effectively inhibited to form a voltage difference, a lithium battery is protected, and the service life is prolonged.

Description

technical field [0001] The invention relates to an electric tool, in particular to an electric tool capable of realizing dual-voltage platform conversion. Background technique [0002] In the prior art, traditional battery packs used in cordless electric tools generally exist in the form of a specific nominal voltage, and common battery packs have two voltage platforms of 18V and 36V. Generally, 18V battery packs can only be used with 18V power tools and chargers, while 36V battery packs can only be used with 36V power tools and chargers. Because the battery packs of the two voltages are not universal, the actual use of battery packs and There are more types of chargers, and the resource utilization rate is not high, which will also increase the purchase cost of users significantly. [0003] Therefore, in order to effectively simplify the types of battery packs and chargers and improve the flexibility and portability of power tools, how to provide a battery pack capable of ...

AI Technical Summary

Problems solved by technology

[0005] In addition, there is a great potential safety hazard in adopting the technical solution of the above patent, due to the repeated charging and discharging of the battery pack in normal use by the user, coupled with the self-consumption of the protection board inside the battery pack and the self-consumption of the battery cells that have been left standing for a long time The two battery packs in the battery pack will generate a certain port voltage difference. When the port voltage difference is large, see Image 6 (Wherein, Va and Vb represent the port voltages of the two battery packs respectively, and I is the current waveform diagram after the two battery packs are connected in parallel), because the internal resistance of the lithium battery is small (usually milliohm level), the two batteries The moment when the groups are connected in parallel will generate a large mutual charging current (the battery pack with high port voltage charges the battery pack with low port voltage), and then tends to charge at a large rate, and the current becomes smaller as the voltage difference becomes smaller until the two port voltages exactly equal

This high-rate charging will cause the charging speed of the lithium battery to be too fast, which not only greatly shortens the service life of the lithium battery, but also brings certain safety hazards to the use of electric tools.

[0006] Therefore, the technical content disclosed in the above-mentioned patents only provides a conceptual solution for a power tool power supply that can realize dual-voltage output, and its circuit principle is not suitable for actual operation and implementation. to make further improvements and

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