China Reliable Li-ion Electric Wrenches Supplier

BOSI Tools is a Li-ion electric wrench manufacturer from China, offering both the Li-ion Brushless Wrench and the Li-ion Brushless Dual-Purpose Wrench. A high-quality brushless motor delivers 350 N·m of peak torque, and the dual-purpose square drive design allows the tool to instantly transform into an electric drill or screwdriver drill.

Intelligent self-release and adjustable torque control make bolt fastening more precise and safer — BOSI provides an efficient, cordless tightening solution for steel structure installation, automotive repair and disassembly, and equipment maintenance through high torque and multi-functional conversion.

Different working conditions demand different tools, so please feel free to contact us for a customized selection solution.

Working Principle

The core of a Li-ion electric wrench is to convert the battery's electrical energy into rotational impact pulses via a brushless motor, outputting instantaneous high torque through a hammering mechanism to tighten or loosen bolts. The BOSI Li-ion Brushless Wrench is equipped with a high-quality brushless motor.

Once powered by the battery, the rotor, after speed reduction and torque amplification through a planetary gear set, drives an active hammer to rotate. During the free-spinning phase as the bolt is run down, the hammer and anvil rotate synchronously, with the speed maintained in two gears: 0–2,000/0–2,600 r/min.

When the bolt seats against the workpiece and resistance increases sharply, the hammer, guided by an internal cam slot, is forced to retract and compress a spring to store energy. It then disengages and surges forward, violently striking the anvil and producing a brief, powerful pulse of torque, peaking at 350 N·m. This cycle of "hammer strike—disengagement—impact" repeats dozens of times per second, with the operator's wrist experiencing minimal reaction force.

The Dual-Purpose Wrench adds a square drive shaft design to this foundation; by switching to the 1/4" hex shank mode, it transforms into a screwdriver drill, instantly becoming an electric drill for drilling holes or a screwdriver for driving screws. The intelligent self-release function automatically releases residual pressure after high-torque fastening, preventing bolt over-tightening. The torque adjustment feature controls the output intensity.

The entire series is equipped with a high-capacity 20V/4.0Ah battery, and a tungsten steel drive shaft offers high hardness and wear resistance. The one-button battery level check makes runtime management intuitive and controllable.

How to Choose the Right Li-ion Electric Wrench?

The primary consideration when choosing is whether the drilling and screwdriving functions are needed. For pure bolt fastening and removal tasks (final tightening of steel structures, tire removal, large equipment bolts), the Li-ion Brushless Wrench focuses on impact fastening, with 350 N·m of torque and intelligent self-release for high efficiency and reliability.

If the job also requires drilling holes or driving screws (such as needing to pre-drill a hole before fastening a bolt when installing a bracket), the Dual-Purpose Wrench can switch its square drive to a 1/4" hex shank and become a drill/driver, completing both drilling and bolt fastening with a single tool and reducing the number of tools to carry.

Common Problems and Solutions

Our Li-ion Electric Wrenches vs. Other Brands: Why Choose BOSI?

The BOSI Li-ion Electric Wrench is centered on a brushless motor with 350 N·m of peak torque. The dual-purpose square drive shaft design breaks through single-function limitations, offering more flexible multi-scenario adaptability at the same torque output.

Safety Precautions for Use

Battery Safety

Use the original charger for charging. Protect the battery from high-temperature exposure and immersion in water. Store with a 30%–50% charge.

Before starting work, use the one-button battery level check to assess runtime and prevent unexpected power loss mid-task.

Socket Matching

Always use impact sockets that match the bolt specification and the 1/2" square drive. Substituting with standard sockets is strictly prohibited.

When installing, push the socket in until the spring-loaded detent ball fully pops out and locks it. Test by pulling gently to confirm it is secure before starting work.

Torque and Self-Release Function

When using for the first time, test the effects of the intelligent self-release and torque adjustment on scrap material to become familiar with the output intensity of each setting.

After the final tightening of critical bolts, use a calibrated torque wrench to check the value. It is normal for the self-release function to automatically release residual pressure; do not forcibly hold down the switch.

Dual-Purpose Switching

When switching the square drive shaft to the electric drill / screwdriver drill mode, always wait for the motor to come to a complete stop. After installing a drill bit or driver bit into the 1/4" hex shank, perform a test run to confirm there is no wobble.

In drilling mode, the torque clutch does not engage, so the tool must be held with both hands to prevent torque reaction.

Operating Posture

When removing bolts with high torque, hold the tool with both hands, stand with your feet firmly planted, and position your body out of the plane of rotation.

There may be kickback the moment a bolt shears off or when a rusted, seized bolt suddenly breaks loose; pay attention to maintaining a stable stance.

Maintenance and Storage

If not used for an extended period, remove the battery and store it separately, recharging it once a month. Although the tungsten steel drive shaft has high hardness and is wear-resistant, it is still recommended to check the gearbox lubrication annually.

Keep the socket square drive and the square drive shaft clean, and apply a thin layer of anti-rust oil. Store the tool body in a dry place, and protect it from being crushed by heavy objects.