When a car is parked for a long time, should the positive or negative terminal of the battery be disconnected?
2 Answers
When a car is parked for a long time, the negative terminal of the battery should be disconnected. This is because most modern cars have a negative ground system, so even if there is an operational error, it won't pose a danger. However, if the positive terminal is disconnected incorrectly, it could damage the battery or even cause a fire. When a car is parked outdoors for an extended period without being started, the battery can completely discharge in about a month, making it impossible to start the car. If the car is only parked for two or three days, it won't have a significant impact. It is recommended to start the car once a week and let it run for about 5 to 10 minutes to recharge the battery. If it's not possible to start the car once a week, the negative terminal of the battery should be disconnected to prevent discharge. When the car is ready to be used again, simply reconnect the terminal, and the car should start immediately.
In all my years working with cars, when it comes to disconnecting battery terminals for long-term parking, my advice is to always remove the negative terminal first. If a car sits idle for weeks or even months, the battery can easily drain. If you only disconnect the positive terminal, the vehicle's metal body remains connected to the negative terminal. Should any tools or debris accidentally touch the positive terminal or nearby metal parts, it could cause a short circuit and fire—way too risky. Removing the negative terminal is much safer as it completely breaks the circuit, preventing accidental discharge or power drain from electronics. I once parked my car in the garage for six months after disconnecting the negative terminal, and the battery held its charge remarkably well—it started up almost without delay. Remember not to overtighten the wrench when loosening the nut to avoid damaging the battery terminal, and I’d recommend wrapping some insulating tape around it to keep dust out. For long-term parking, also check tire pressure regularly to prevent dry cracking and avoid exposure to wind and rain to slow down aging.
