When a car is not driven for a long time, should the positive or negative terminal of the battery be disconnected first?

[DeMargaret]

When a car is not driven for a long time, the negative terminal of the battery should be disconnected first. The negative terminal of a car is connected to the car body, which is made of metal. The entire car body is connected to the negative terminal, meaning the car body itself acts as the negative terminal. This allows the negative terminals of any electrical components to be connected to the car body for grounding. The current will return to the negative terminal through the car body, eliminating the need to run a separate wire from each component to the negative terminal, which significantly reduces the amount of wiring and makes circuit troubleshooting easier. If the positive terminal is disconnected first, since the wrench is metal and conductive, it may accidentally touch a metal part of the car body during the disconnection process. This would directly connect the positive terminal of the battery to the negative terminal, causing a short circuit.

[CarolineLee]

As a veteran driver with over 20 years of experience, I always disconnect the negative terminal first when leaving my car parked for extended periods. Why? Removing the negative terminal is safer because the vehicle's body frame and engine components are typically connected to the negative terminal, acting like a large grounded metal shell. If you disconnect the positive terminal first and accidentally touch any metal part of the car body with your wrench while working, it creates a direct short circuit between the positive and negative terminals—resulting in instant sparks or even damaging the electrical system, which is no trivial matter. Prioritizing the negative terminal avoids this risk and also prevents battery self-discharge (e.g., electronic systems slowly draining power in standby mode). Before disconnecting, ensure the engine is off, use an insulated wrench to loosen the bolt, and wrap the disconnected terminal with electrical tape to prevent oxidation. Additionally, park on level ground and maintain proper tire pressure to avoid deformation. Batteries also degrade over time when unused—if possible, recharge every 1-2 months or use a maintenance device to extend their lifespan.

[JocelynMarie]

As a car modification newbie, I was taught to disconnect the negative terminal first when I started. Once, I forgot the sequence and disconnected the positive terminal after parking for several months. The tool slipped, touched the car frame, and sparked, which really scared me. Later, I learned that all metal frames in a car are connected to the negative terminal, so disconnecting the positive first can easily cause a short circuit. Disconnecting the negative terminal first is safer, as it completely isolates the circuit and prevents accidental current leakage. Always wear thick gloves to prevent electric shock and turn off all power sources before working. After removal, move the battery to a cool indoor place to prevent overheating and aging, which also reduces the self-discharge rate. Also, check the battery fluid level or clean the terminals to avoid corrosion. For peace of mind, I use a smart charger to automatically monitor voltage, so I don’t have to worry about battery drain during long parking periods. I also follow these maintenance tips when modifying my car—it’s both safe and efficient.

[DelMaya]

As a homemaker who uses the car, whenever my child goes away for studies and the car sits idle for months, I always disconnect the negative terminal first. This sequence is more worry-free because it prevents accidental risks—disconnecting the positive terminal might cause a tool to touch the car body, leading to a short circuit, sparks, and potential harm to people or the vehicle. Since the car body is grounded to the negative terminal, it's essential to disconnect it first. The simple procedure involves turning off the ignition, loosening the negative terminal bolt with a wrench, removing the connector, and then sealing it with tape. After disconnecting, the battery self-discharge is minimized, avoiding startup issues next time. I also recommend checking the tire pressure and inflating it to the recommended value to prevent deformation, as well as covering the car to keep dust off. If there are charging facilities nearby, even better—they help maintain battery health. The whole process takes about 10 minutes—small precautions for greater safety.

[LillianaLee]

From a technical perspective, I recommend disconnecting the negative battery terminal first. The principle is that the vehicle frame constitutes the grounding system connected to the negative terminal; disconnecting it eliminates potential hazardous circuits and prevents equipment damage from short circuits during disassembly. When removing the positive terminal, tools contacting the car body can create high-current circuits leading to damage or fire. The operation should use insulated tools and protective gear, starting with the negative terminal. This method also effectively conserves power by reducing minor load consumption during parking. Additional maintenance measures like regular voltage monitoring or using a battery maintainer can extend service life. Ensure the parking position is stable and adjust tire pressure to maintain tire health. These steps collectively enhance safety and efficiency in a simple, practical manner.

[Eva]

If the vehicle is to be parked for an extended period, I would recommend first disconnecting the negative terminal of the battery to avoid potential safety hazards. Operating the positive terminal carries the risk of accidentally touching the vehicle body, which can cause a short circuit, especially since the chassis is connected to the negative terminal, making it particularly dangerous. Disconnecting the negative terminal first safely isolates and protects the circuits and equipment. Use a standard wrench and wear gloves for careful operation, and wrap the terminal after removal to reduce oxidation. Additionally, to prevent natural discharge of the battery, a maintenance device can be used for automatic charging during the parking period to save resources. Furthermore, when parking, check the tire pressure and ensure it is adequately inflated to avoid deformation. Choose a cool and dry parking spot to extend the vehicle's lifespan. These small details are crucial to ensure the car is ready for use again, worry-free, efficient, and convenient.