How Long Can I Leave My Car in Accessory Mode?

You know that sinking feeling you get when you realize you’ve left your car lights on? And you have to go back out into the cold to switch them off? Well, here’s some good news: You can leave your car in the accessory mode without worrying about the battery.

How Long Can I Leave My Car in Accessory Mode

In fact, it’s actually recommended that you do this every once in a while to keep the battery healthy.

But how long can you leave it in the accessory mode without damaging your car? Keep reading to find out!

What Is Battery Accessory Mode?

Battery accessory mode by definition is the auxiliary battery setting for a car to allow external charging. This can be done, for example, to keep your phone charged while using it as a GPS.

It also allows your music system to run without starting up your vehicle, or any other electronic device that requires power directly from the battery.

Battery accessory mode is best to use when your vehicle is not running or when you aren’t driving for longer periods of time.

Does Accessory Mode Drain Battery?

The short answer is no, accessory mode does not drain the battery. However, this varies from device to device and depends on the accessories you’re using.

The reason accessory mode is thought of as a battery-draining culprit is that when in accessory mode, different devices in your car may be getting the power from the battery and consuming them. If you can ensure that all the accessories are turned off, merely having the accessory mode turned on won’t cause any battery draining issue.

How Long Can I Leave My Car in Accessory Mode?

If you’re wondering how long you can leave your car in accessory mode, the answer is that it depends on the type of battery.

You can leave your car in the accessory mode for days at a time as long as any accessory is not draining the battery.

If you have a traditional 12V lead-acid battery, as most cars use, there’s no problem with leaving your car in the accessory mode for 35 to 45 minutes with the music system or other internal features turned on.

However, if you have a lithium-ion battery, don’t leave your car in the accessory mode for more than 4 hours at a time.

Car Battery Dies in Accessory Mode – What to Do?

If you are having problems where the battery of your car dies after being left in accessory mode, there are several things you can do.

  • Check to make sure that all the accessories in your car are turned off when you’re not using them. This includes the radio, the climate control, and the headlights.
  • If you have a traditional 12V lead-acid battery, make sure to recharge it after every time you use it in the accessory mode.
  • If you have a lithium-ion battery, you should consider getting a battery charger to help keep the battery healthy.

Leaving your car in accessory mode is a great way to power your devices without having to start up the vehicle. As long as you’re aware of the best practices for using this mode, you can keep your car’s battery healthy and fully charged.

The Purpose of Accessory Mode

Accessory mode keeps many of your car’s electrical components on without the engine running. This includes accessories like the interior light, radio, and power windows.

Once the accessory mode is disengaged by whatever mechanism you have for starting your car (push-button start, keyless entry fob) all these things remain off until you start your car with ignition.

The Problem with Accessory Mode

The two main problems with accessory mode are:

One, The biggest problem with leaving your car in accessory mode day after day is the damage it does to your battery. A lithium-ion car battery has a lifespan of about 3-5 years, and leaving it in accessory mode takes its toll on this battery life. 

Secondly, As well as hurting your battery lifespan, accessory mode puts unnecessary wear on other car components too. Things like your radio and interior lights can be negatively affected by leaving it in the accessory mode for extended periods of time.

 Is it Bad to Keep a Car on Accessory Mode?

There are a few things you should be aware of when it comes to using the accessory mode in your car.

The biggest thing you need to worry about is damaging your battery. If you leave your car in accessory mode for too long, you can wear down the battery life and eventually cause it to die.

Another thing to be aware of is the extra wear and tear you’re putting on your car’s components. By leaving your car in accessory mode, you’re asking a lot of your alternator, starter, and other electrical components.

Things to Avoid in Accessory Mode

The main issue is that something called parasitic draw begins to drain the battery even when the car is turned off and no accessories are getting power from the battery.

Here are some things to avoid doing when leaving your car in the accessory mode for extended periods of time:

  • Do not let your car sit idle for long. If this happens, you will drain the battery and then have to jump-start the car to get it running again. This can cause problems with your alternator or battery if it is drained too far.
  • Do not leave accessories on for extended periods of time. Only use power when you need it. Keeping the radio, heater, AC, or interior lights turned on while you are not in the car can cause things to go bad sooner than expected.

Can I Charge My Phone While the Car is in ACC?

If your phone is dead while you’re left in accessory mode, it’s useful to charge rather than not! Connect your phone to the power outlet in your car using an adequate charging cable.

Your car’s accessory port might only charge devices at a maximum of 500mA, which is rather slow compared to most chargers. This means it will take much longer for your phone to charge while you’re left in accessory mode.


So, is it bad to keep a car in accessory mode? In short, no – as long as you’re not doing anything that’s draining the battery. You need to make sure that you are not using this feature carelessly to the extent where the battery can get drained out completely leaving you in suffering.

If you have any other questions about how to use accessory mode or want advice on what else you can do to take care of your car’s battery, don’t hesitate to reach out!

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