Why always remove the negative pole to cut off the vehicle battery power？

When a vehicle is parked for a long time, if the battery is not disconnected, the battery will lose power and fail to start after a month at most. In order to prevent the battery from losing power, it is usually necessary to disconnect the battery. To disconnect the battery, it is generally not necessary to remove both the positive and negative poles, but only one terminal. As long as the battery cannot form a circuit, it will not discharge to the outside. 

However, there are some rules for whether to remove the positive or negative pole. You cannot just remove the battery wire at will. Normally, you can remove the negative pole of the battery. The reason is very simple, which is to prevent the wrench from hitting the metal part of the vehicle body during the disassembly process and causing a short circuit, which will damage the battery.

The entire body of the vehicle can be regarded as the negative electrode of the battery. The body of the vehicle is made of metal and is conductive. In order to be more reliable and make the circuit simpler, most of the wires on the vehicle are positive wires and there are no negative wires. When the negative electrode is needed, it is directly connected to the body of the vehicle, commonly known as grounding. Finally, the body of the vehicle is connected to the negative electrode of the battery with a thick wire. In this way, the negative wire of any electrical appliance can be connected to the body of the vehicle nearby to achieve the shortest wire.

If you remove the positive pole of the battery, since the wrench is made of metal and is conductive, it is very likely to touch the metal part of the vehicle body during the back and forth rotation. If it touches, it is equivalent to the battery electricity coming out of the positive pole, passing through the wrench to the metal part of the vehicle body, and then to the negative pole of the battery. The circuit forms a loop but no load passes through it. This phenomenon in the circuit is a short circuit. A huge current will be generated during a short circuit, which will not only damage the battery, but also the dismantling personnel may be injured. 

If you remove the negative terminal of the battery, no matter how you turn the wrench, there will be no problem, even if it touches the metal part of the vehicle body, because they are all negative terminals of the battery, and there will be no short circuit problem. As long as you don't touch the positive terminal, there will be no problem, and the positive terminal is wrapped in a shell and cannot be touched anyway.

Therefore, removing the negative pole is to prevent accidents during the disassembly process and minimize the risk.

But the negative pole of some vehicle batteries is very hidden, and you don't have a suitable wrench. What should you do? Can't you remove the positive pole? Yes, you can, but you need to be careful. When disassembling, you can wrap the other parts of the wrench with cloth or tape, especially the back half, to form an insulating film. Even if it touches metal, it will not conduct electricity, and there is basically no danger.