How long can a car battery last if it's not in use? 

A car battery can last for 2 to 3 months if it is fully charged, but the duration depends on the size of the battery. 

If you don't use your car for a long time, it is recommended to give it a charge every once in a while because the battery will automatically lose some电量.

蓄电池的自放电速度因型号而异, 一般而言，汽车电瓶每天会消耗百分之2至3的电量。

Car batteries, also known as lead-acid batteries, work by converting chemical energy into electrical energy. 

The life span of a car battery can vary from 1 to 8 years, depending on the condition of the vehicle and the type of battery. 

If you have a deep cycle battery, it can last up to 3 years. If you have a AGM battery, it can last up to 5 years.

To extend the life of your car battery, it's important to keep it charged. 

If you're not using your car for a long time, you should consider using a smart battery charger to maintain the battery's charge. 

This will prevent the battery from self-discharging and keep it ready for use when you need it.