How Long Can a Car Run Without Being Started?

The concern of running a car for an extended period without it being started can lead to problems in the battery and starter. The average starter can last for decades, but the battery—a critical component—has a much shorter lifespan. Understanding what happens to your car's battery and starter when it is not used can help you avoid costly repairs.

The Condition of the Starter

Car starters are robust and designed to handle long periods of inactivity. An average starter, like the Johnson Controls model with a flooded battery (1000 Cold Cranking Amps/800 Cranking CCA) rated for 3 years, can sit unused for decades without significant issues, especially if it is protected from moisture. However, the quality of the grease used in some starters can deteriorate over time, which may affect their long-term performance. Some starters, particularly those built over 50 years ago, can still work after decades of non-use. Nevertheless, it is generally not recommended to leave a car unused for extended periods.

The Impact on the Car Battery

The car battery is a critical part of the vehicle's electrical system. Modern cars have numerous electronic components that require a constant power supply, even when the engine is off. These components, such as electronics, sensors, and control modules, keep the car's memory, security systems, and infotainment systems operational.

Car batteries are designed to last between 3 to 6 years, depending on various factors. Modern-car batteries are more susceptible to early failure due to the constant draw of power from the residual electronic systems. For example, in vehicles built from 1996 onwards, equipped with OBD-2, the average lifespan of a battery is around 3 to 4 months if left idle without being started or charged.

If the vehicle is older, such as one from the 1970s with no clock and an old mechanical-dial radio, it is possible to start the car after several months without it being used, but this is not advisable. An idle car's battery will self-discharge over time, even if the cables are disconnected. Some batteries can survive for years with a battery tender connected, while others may last just weeks on modern cars without maintenance.

Keys to Extending Battery Life

To prolong the life of your car's battery, consider the following tips:

Use a battery tender: A battery tender, also known as a trickle charger, can keep your battery charged and reduce the likelihood of deep discharge. Disconnect the battery: If storing your vehicle for a long period, try to remove the battery or disconnect it from the car to avoid any residual electrical draw. Environment: Extreme temperatures, especially cold, can accelerate battery degradation. Keep your vehicle in a garage or a sheltered area during winter. Regular maintenance: Regularly check and maintain your battery to ensure it is in good condition. This includes cleaning terminals and ensuring no corrosion buildup.

In conclusion, while a car's starter can endure long periods of non-use, the car's battery and other sensitive electronics are more susceptible to early failure. Proper maintenance and care can help extend the life of these critical components, ensuring your car stays reliable and efficient.