When leaving a car, it is generally enough to shut down the engine and ensure that all accessories are turned off. Most modern cars have an ignition switch that, when turned off, shuts down the engine and cuts power to electrical systems that rely on the engine for power. This includes the vehicle's lights, radio, air conditioning, and other electrical components directly connected to the engine.
However, there are a few things to keep in mind to ensure you're not unintentionally draining your car's battery or wasting energy:
Turn off all accessories: In addition to turning off the engine, make sure to turn off any accessories that may still be running, such as the radio, headlights, interior lights, air conditioning, and any other electrical devices.
Check for interior lights: Many modern cars have automatic interior lights that turn on when you unlock or open the doors. Make sure all doors are closed and the interior lights are off before leaving the car.
Unplug chargers and devices: If you have any devices charging through the car's USB ports or power outlets, unplug them when you leave to avoid draining the car's battery unnecessarily.
Extreme temperatures: In very hot or cold weather, it's a good idea to check that the air conditioning or heating systems are turned off, as they can draw power even when the engine is off.
While turning off the engine and accessories is usually sufficient, there may be specific circumstances where you might want to disconnect the car's battery completely. For instance, if you plan to leave your car parked and unused for an extended period (several weeks or more), disconnecting the battery can help prevent any slow drain on the battery from auxiliary systems.
In most cases, though, simply turning off the engine and ensuring all accessories are off will be enough to prevent unnecessary energy consumption and avoid draining your car's battery.