Leaving your air conditioner running while parked overnight can indeed drain your vehicle's battery. The air conditioner compressor requires power to operate, and if the engine is not running, it relies on the battery to provide that power. The battery's capacity is limited, and running the air conditioner for an extended period without the engine running can deplete the battery charge.
Car batteries are primarily designed to provide the necessary power to start the engine, as well as to operate the vehicle's electrical systems when the engine is off. However, they are not typically designed to power high-energy-consuming devices like air conditioners for long periods.
If you leave your air conditioner running while parked overnight, it may drain the battery to a point where it can no longer start the engine. In such cases, you would need to jump-start the vehicle or use a battery charger to replenish the battery's charge.
It's worth noting that the exact time it takes for the battery to drain depends on several factors, including the battery's condition, capacity, and the efficiency of the air conditioner. Additionally, the drain on the battery can be influenced by other electrical systems in the vehicle, such as lights or entertainment systems, that may also be in use.
To avoid draining the battery, it's generally recommended to turn off the air conditioner and any other non-essential electrical devices when the engine is not running.