Skip the auto shop - Our mechanics make house calls

Q: What Is Key-Off Battery Drain?

asked by on

What is key-off battery drain?

A: A battery drain is a term for a component i...

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.

Was this answer helpful?
Recommended services
Get a Quote

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: No crank no start

No crank conditions are inherently caused by bad connections. The question to ask is where that bad connection is. As simple as this sounds, identifying a bad connection isn't a factor of what a physical connection looks like. You can...

Q: Car clicking when I turn the key

A low battery is the most common cause of a no-start. A qualified technician, such as one of our YourMechanic experts, will inspect and test the battery, charging system, and starting system to confirm any diagnosis.

Q: Why won't my truck charge the battery?

Hi there. Several situations could prevent adequate charging from an otherwise healthy electrical system. These include poor connections at the batter posts, power cables at the alternator, ineffective grounding between the battery, chassis, and engine (good connections and large enough...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...