How Long Can a Car Battery Last Without Being Used?

[MacHope]

If a car is left unused, the battery can last for about two months. It is recommended to disconnect the positive and negative terminals of the battery (to avoid natural discharge). However, for cars in poorer condition, the battery may lose power within about a week. Driving the car normally for one to two hours can restore the battery to its normal charge. If the battery is severely depleted to the point where the engine cannot start, a jump-start may be required to reactivate it. A car battery, also known as a storage battery, is a type of battery that works by converting chemical energy into electrical energy. The commonly referred-to car battery is a lead-acid battery, which is primarily made of lead and its oxides, with sulfuric acid solution as the electrolyte.

[StIsla]

As a veteran driver with twenty years of experience, I've seen too many cases of batteries going dead. A regular battery can drain in just two weeks of inactivity, even shorter in winter. Last year, my neighbor's car sat idle for a month and the battery was completely dead, costing him 800 yuan for a replacement. Batteries parked outdoors degrade faster than those in garages, and cars with electronic anti-theft systems consume more power—luxury cars like BMWs can fail to start after just ten days of inactivity. In the humid south, battery terminals are prone to corrosion and leakage, while in the cold north, low temperatures can freeze the electrolyte. The key is to start the car for twenty minutes each month to recharge the battery or disconnect the negative terminal. Last week, the owner of an auto repair shop told me that 30% of the battery replacements at his shop before winter were due to long-term parking.

[AdrianaLee]

A friend in auto repair told me that battery life depends on three factors: usage duration, temperature, and additional equipment. A new battery can last a month in winter, while an old battery over three years old might only last ten days at most. Vehicles with dashcams running 24/7 surveillance or modified audio systems could deplete their batteries in just five days. Last year, I used a current clamp to measure and found that some German cars still have a dark current of 0.3 amps after being locked, whereas regular cars only have 0.05 amps. The safest bet is to keep an emergency power supply handy. For long-term parking, it's better to disconnect the battery's negative terminal. Their repair shop often deals with cars that have been parked for three months and need a jump start—once towed back, the battery is usually beyond saving.

[LaAdelyn]

Back when I was learning to drive, the instructor said that lead-acid batteries are like fish out of water. They self-discharge at a rate of 1% per day when idle, but actual discharge is also affected by temperature: at 25°C, they lose 20% charge per month, while at -10°C, they can lose up to 30%. Last month, my Nissan Sylphy sat in an underground garage for three weeks, and the dashboard was dim when I tried to start it. Later, I bought a smart charger that automatically cuts off when fully charged, which is more convenient than a regular charger. Now, I always connect it before a business trip, and the car starts right up when I turn the key upon returning. The modification shop mentioned that AGM batteries with start-stop functionality are more resistant to discharge, but replacing one costs over two thousand yuan.