What is key-off battery drain?
A battery drain is a term for a component in your vehicle that is staying on and draining battery power even after you have shut the car off and exited the vehicle. It could take a day for it to completely drain the battery and make the vehicle unable to start, or it could take a week or more.
There are many reasons for this issue. One reason is that the vanity mirror could have a light that stays on because the cover is not closed, or a glove box that is left open and the light stays on. Another possible reason is that someone turned on an interior light and forgot to shut it off. It could also be due to a bad installation of an aftermarket alarm system or an aftermarket stereo. Most issues stem from driver error, but that is not always the case. It also depends on the year and make of the car; older cars are less susceptible to this.
If you have a vehicle that was manufactured since 2000, then you could be having computer issues. Vehicles today are getting more and more sophisticated with technology and now have many onboard computers. In the late 1990s and early 2000s, vehicles had only one computer. Now a vehicle could have over 30 different modules that stay on even after you shut off your vehicle. All of these computers are supposed to go to sleep or shut down completely after a certain amount of time. Sometimes they don't and they need to be reprogrammed to do so. If you leave accessories plugged into your cigarette lighter, as people often do with a phone charger or a GPS, your battery could get drained. Some vehicles now have televisions in every headrest, which could be staying on after the vehicle shuts off. A trailer towing package could also cause an issue if you leave a trailer connected to the vehicle.
I recommend that you unplug any accessory when you are not in the vehicle for many reasons, not just battery issues. If your vehicle is having issues starting, such as sluggish or slow starting one day and normal starting the next, this could be an issue. I recommend that you have your vehicle checked over by a certified technician for electrical issues and try to keep all accessories disconnected when not using your vehicle. This will help prevent issues from happening. If your battery is dead](https://www.yourmechanic.com/services/battery-is-dead-inspection), you can have a mobile mechanic from YourMechanic replace it for you at your home or office.
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