Do Hazard Lights Drain the Battery? Keep Your Battery Healthy

Emergency or hazard lights are so insignificant that lots of people don’t consider their power consumption level. Hence, they often wonder, do hazard lights drain the battery?

The answer is yes, hazard lights drain car batteries like every other electronic in the vehicle. 

But you have to know more about this topic to make sure that you don’t accidentally keep them turned on and let the battery die. Read the article for a clear idea about the topic. 

Do Hazard Lights Drain Battery?

You have already got the answer to the question. And, I know that lot of you have probably been stunned hearing that it can kill the battery for good. 

Now, let me explain the rate of its power consumption and how long your car battery can keep up with the demand. 

The first thing you have to understand is that car batteries are rated in Ah or Amp-hour. 

It indicates the amount of electricity it can deliver for a certain period. Let’s assume that a battery is rated 12Ah.

What it means is that it can deliver 1 Amp for 12 hours, 2 Amps for 6 hours, or 12 Amps for 1 hour. You have got the idea. 

Now, your car battery must have a higher capacity than the example. For group 24 batteries the ideal capacity is around 80Ah.

I have also done some research on the electricity demand of the standard turn signal lamps. And, they tend to take about 2 Amps to operate. 

Here, I am about to do the final calculation which is slightly complex. So, give your full attention to this part. 

I am assuming that you have turned on all 4 blinkers or emergency lights. Therefore, the current draw should be 8 Amps.

But the lights blink half the time. It will be okay to consider the total amount of electricity required for them to operate in an hour is 4 Amps.

Finally, divide the total capacity (80Ah) by the demand (4A), and you will get 20 hours of runtime. 

If any of the stated values do not match your car or hazard lights, recalculate the whole thing, and you will get the time. 

How Long Can Hazard Lights Stay On Before Battery Dies?

Here, you have to understand a few things. A car battery can be discharged to a certain level where it can’t start the engine anymore. 

You can consider that state as half-dead. And, it can be fully discharged when you can consider it dead for good. 

If we talk about the same example given above, you will see that the car lights are still flashing when the battery will be down to 11 volts. 

But you won’t be able to start the engine. Limiting the depth of discharge at 75% will give you the maximum hazard light runtime without letting the battery die.

According to my calculations, you must not let all 4 emergency lights be turned on for more than 15 hours. 

That is a rough calculation with lots of variable factors. I hope that you have got the overall idea. 

Is It A Problem While Hazard Lights on When Car Is Off?

When you use the electronics on the car while the engine is running, the alternator takes care of the power demand. 

But things start getting uglier as soon as all pressure comes down to the battery. 

You should not keep the hazard lights on for long when the car is off

Besides draining the battery, it can also face a corrosion issue. Also, it may shorten the signal switch connection which is faced by lots of car owners.

Frequently Asked Questions (FAQs):

How long does it take for hazard lights to drain the battery?

You will be surprised to know that most of the hazard or emergency lights can drain your car battery within 10 minutes without the engine running. 

How long can I leave hazard lights on?

The answer varies depending on the car model. Because LED hazard lights and larger battery capacity can let you leave the emergency lights on for the whole night. 

How fast do hazard lights drain battery?

I have already answered the above questions. From 10 minutes to an hour or even more than 8 hours is the time a hazard light takes to drain the battery.  

Do a vehicle’s hazard lights work when the car battery is dead?

Weak car batteries that can’t start the engine may still be able to turn the hazard lights on. But a fully discharged battery won’t be able to turn the lights on. 

Do emergency lights drain battery? 

The answer is yes, emergency lights are perfectly capable of draining the car battery. But it is not the case when the alternator is running. 


Do hazard lights drain battery? Yes, and you have got all the necessary info so that the car battery doesn’t die on this silly matter. 

Whatever you do, don’t leave those lights unattended for hours. In fact, don’t keep any electronics running while the engine is off. 

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