Should the car power disconnect switch cut off the positive or negative terminal?

[OHarmony]

To save space, cars use a single-wire system where the battery's negative terminal is directly connected to the vehicle frame. The negative terminals of onboard electrical devices can simply be connected to the car body with a nearby wire. Therefore, when disconnecting power, you only need to remove the battery's negative terminal, eliminating the risk of wires sparking. Here are relevant explanations: Negative terminal: The car's negative terminal is connected to the vehicle body, meaning the entire car body serves as the negative terminal. This allows any electrical component's negative terminal to be grounded to the car body, with current returning to the negative terminal through the body. This eliminates the need to run separate wires from each component to the negative terminal, significantly reducing wire usage and simplifying circuit troubleshooting. Positive terminal: If you disconnect the battery's positive terminal instead, since wrenches are metal and conductive, accidentally touching any metal part of the car body during removal would directly connect the battery's positive terminal to the negative terminal, causing a short circuit.

[DakotaMarie]

When I need to disconnect the car battery, I usually choose to disconnect the negative terminal rather than the positive one. The reason for this is to avoid the risk of a short circuit, as the negative terminal is connected to the vehicle's grounding system. If I were to touch the positive terminal, a wrench or tool coming into contact with any metal part of the car frame could create an instantaneous current return path, causing sparks to fly. In severe cases, this could damage electrical components or even start a fire, which must be prevented during safe operations. I recommend first using an insulated wrench to loosen the screw on the negative terminal clamp, ensuring it is kept away from the battery post, and then securing it with a rope or plastic tie to prevent accidental contact. For long-term parking, this procedure effectively prevents the battery from naturally discharging and losing power. However, remember to wait a few minutes after disconnecting before reconnecting, allowing the car's computer system to safely reset without losing settings. Proper maintenance of the car's power system is an essential skill. Since learning this method, I've always followed it, ensuring safety and peace of mind.

[VonMaria]

During my days of tinkering with cars, I prefer disconnecting the negative terminal of the battery to cut off the power. Once, while helping a friend with his car, I accidentally touched the positive terminal clamp, causing sparks to fly from the car body and nearly burning out the battery controller. From that lesson, I learned that disconnecting the negative terminal is safer because it's the ground connection. Once disconnected, the entire circuit is broken, and touching the positive terminal anywhere won't create a short path. In practice, I usually use an 8mm or 10mm wrench to loosen the negative terminal clamp screw and move it aside—simple and practical. If the car won't be used for an extended period while parked, disconnecting the negative terminal is the most effective way to prevent power leakage. However, I remind myself that after reconnecting, I might need to adjust the time settings, as modern cars often require this. My conclusion: safety first, and working on the negative terminal is more hassle-free.

[OAlejandro]

When I first learned to drive, I was also curious about this question. It's more reliable to disconnect the negative terminal first when cutting off the car's power. The negative terminal is connected to the car's frame, which serves as the return path for the current. Disconnecting it safely cuts off the circuit. If you touch the positive terminal, tools coming into contact with the metal body of the car could cause a short circuit and damage the vehicle. I recommend using a wrench to loosen the screw on the battery's negative terminal and then moving it aside for an easy operation. Disconnecting the battery when the car is parked to prevent power leakage is a good habit, but don't forget to reset the clock settings after reconnecting to avoid any inconvenience.