Will Emergency Lights Kill Battery? : Let’s Find Out!

Despite our best efforts, we occasionally fail to turn off a certain light or any other electronic gadgets when rushing to get out of the car. And soon enough, we are met with a car that won’t even start. 

One of the things we frequently forget to turn off is emergency lights. These will surely drain a lot of battery but will emergency lights kill battery?

Emergency lights won’t damage or kill your battery until its voltage reaches the 10.5V range. When a battery goes to 10.5 volts, it is considered completely drained. After this voltage is reached, the battery starts sulfation, which will permanently damage it. But it takes the emergency lights a long time before it reaches that voltage.

So, what is the approximate runtime of the battery before it may start damaging? What steps should you take to stop it before something like this happens? 

When Emergency Lights Might Kill Battery?

Emergency lights don’t necessarily kill the battery the moment you turn them on, even when it’s been on for a couple of hours. Depending on your battery’s capacity, it can stay on for a long time before it can start to damage your battery.

Let’s dig deep into the normal draining of the battery and when it starts to become alarming- 

Will Emergency Lights Kill Battery

Draining At A Normal Rate

When turned on, emergency lights will gradually deplete your battery. However, even then, the battery won’t be entirely depleted in an hour. The duration will take for your car’s battery to completely discharge is shown in the table below- 

Emergency Light PowerLow Capacity(38-60 Ah) RuntimeMid Capacity(50-80 Ah) RuntimeHigh Capacity(75-95 Ah) Runtime
7.2W(7.2*4=28.8 W)32-50 Hour42-67 Hour63-79 Hour
10W(10*4=40 W)23-36 Hour30-48 Hour45-57 Hour
12.5W(12.5*4=50 W)18-28 Hour24-38 Hour36-45 Hour
18W(18*4=72 W)13-20 Hour17-27 Hour25-32 Hour
25W(25*4=100 W)9-14 Hour12-19 Hour18-23 Hour
36W (Lightbar)25-40 Hour33-53 Hour50-63 Hour
40W (Lightbar)23-36 Hour30-48 Hour45-57 Hour
96W (Lightbar)9.5-15 Hour12.5-20 Hour19-24 Hour
120W (lightbar)7.6-12 Hour10-16 Hour15-19 Hour

This is based on batteries that are brand-new. Depending on how frequently it is used and driven, your car’s runtime will change.

For better estimation, it is preferable to take into account 50% of the available time. The drain during this time is considered normal draining. 

Draining At An Alarming Rate

When emergency lights are used, the voltage will continue to be 12 until the end of the runtime. However, the voltage will begin to fall as soon as the estimated runtime is done and will eventually approach 10.5V. This is approximately 80% of the full charge.

When a battery drops to roughly 10.5 volts, it is deemed entirely drained even though 80 percent of its capacity remains. Because extending the cycle further can result in severe sulfation, which may permanently harm the plates.

Normal sulfation can be restored, however, soft lead sulfate can crystallize if a battery is over-drained. Charging the car battery will make some sulfation reverse, but any crystallized lead sulfate will stay on the plates. 

Under normal conditions, this sulfate cannot dissolve back into the electrolyte, reducing the battery’s available output permanently.

These are emergency lights draining the battery at an alarming rate. At this point, your battery will start to be damaged by the emergency lights.

Other Factors that Contribute to Killing Your Battery

Along with the normal draining, your car battery is quite prone to the following factors. Each of them is important in the battery’s discharge and eventually kills it.


Self-discharging while sitting idle is a problem batteries face. For example, even when it is kept on a shelf, a normal lead acid battery will naturally lose 0.1V every month.

You may say the amount isn’t a lot. However, if we take into account that a full battery is at 12.72V and a chemically drained battery is at 11.8V, the battery may appear flat after just eight months of inactivity. And the battery wasn’t being used in any way. 

Continual Power Draw 

Electronics accessories in a car like a clock, radio, and alarm system get a small amount of power to keep them functioning while the engine is turned off. The amount of power needed for this is really small but over time, it adds up to a large sum.

And with modern cars, there are other electric systems that are kept running. These all heavily drain your battery and speed up the damaging process of the battery.

Leaving Key Close to Car 

Modern keys work as a radio transmitter. They send signals to the car through radio transmission and we are able to command the car however we like. For example, when pressing the button, the door gets opened, etc.

Before the key sends a signal for any probable command, they establish a connection with the car whenever they are at a close distance. From the car’s part, this always draws a small amount of power to establish this connection. 

And if the key is left nearby, it will continue to interact with the car. This will drain your battery heavily.

Too  Many Short Drives 

Short drives are fun but not so fun for the car’s battery. A car’s alternator needs enough time to recharge the car while they are on. 

But with short drives, there isn’t much time over every time you turn on the car it takes 150-300A power from the battery. This heavily affects your battery and soon the battery will be flat.

Faulty Alternator 

Your battery is what powers your vehicle when you start it. While your vehicle is running, the alternator is what keeps your battery charged. 

Even though you just drove, it could be difficult to start your car if your alternator isn’t working properly. Because your battery won’t receive enough charge, and the alternator won’t be charging it either.

Cold Weather 

Weather has a significant effect on your battery. Both extreme hot and cold weather affects the battery badly. But the cold weather is especially bad. 

Battery performance is known to lose at least 35% when it’s freezing outside. And if the weather goes down it can even lose its performance by up to 50%. Your car itself will show signs that it’s not adjusting well to the extreme weather.

These factors collectively are to blame for the battery’s heavy charge loss and eventual death or serious damage.

What To Do When Your Battery Might Be Dead

What To Do When Your Battery Might Be Dead?

Depending on the battery condition, it will be decided whether your battery simply needs a recharge or it needs to be completely replaced. Cars are good at showing that something is wrong. And you can clearly tell whether the battery or the car starter is the problem.

Now, before replacing your car battery, you need to try to recharge it. If the car is not responding even after a couple of tries then it’s a prominent sign that it needs to be replaced. 

Let’s check out how you can recharge your battery- 

Recharging the Car Battery

The easiest way to recharge is to jump-start the dead car battery. You can do it in two different ways. 

The first process is by using jumper cables with the help of another car. Let’s check the process down below-

The first step is to parallel park both vehicles. Use the parking brake to keep yourself safe. Then, open the hoods of both vehicles and check for the batteries. The majority of batteries are located near a headlight under the hood.

Find the positive and negative connections of the battery. Make sure they don’t have any rust. 

Now, secure the red clamp to the positive post of the dead battery. The second red clamp should then be connected to the positive post of the working battery. The first leg of the connection has been completed.

Connect the black clamp to the negative post of the working battery. You will see an unpainted metal surface right there. The final black clamp needs to be connected to this metal surface after that. This is the earthing point for your car. 

Now, ask the other driver to start his vehicle. How long you need to charge with a jumper cable may vary depending on your car battery. But usually, it will be done in 5-10 minutes. Wait for about a minute right now. After that, you ought to be able to start the engine. 

Wait a few minutes, though, if this doesn’t help and the engine won’t start. To start your car, you must carry out the process twice more after that.

If the battery is completely damaged, jump-starting won’t help revive it at all. This is when you need to replace the battery. 

Replacing of Car Battery

Replacing a car battery can be quite difficult especially if you haven’t done it before. So we do suggest taking the help of a professional. But if you are well versed with car mechanics you can easily get it replaced and save a couple of hundred bucks. 

Here’s a simplified procedure for the home replacement of your car battery- 

  • Lock the doors, switch off the engine, and place the car in park. Be sure the engine has cooled down before looking for the battery. The majority of car batteries are located beneath the hood in the front. The battery may be in the trunk of some vehicles.
  • The two terminals on the batteries are where the cables are attached. They might have plastic covers on them. A negative one in black and a positive one in red. For positive and negative terminals, respectively, there may be a + and – mark.
  • Never cut the positive cord before the negative. By using a wrench, unscrew the bolt that connects the negative connector to the battery terminal. Once released, gently wiggle the cable connectors back and forth to remove it from the terminal. The positive cable should then be removed in the same way.  
  • Now, before removing the battery you need to remove the metal clamps as well. Metal bars or clamps at the base are used to secure car batteries. Loosen the bolt to remove the retaining bar and remove the battery as well.
  • While removing the battery keep it upright at all times as batteries contain corrosive liquid. Check the wires and connectors to make sure they are not frayed or broken.
  • It’s time to place the new battery. But before that check whether the new battery’s position corresponds to the red and black connections. Place the new battery on the mounting shelf and then lower it. The hold-down bar or clamp should be reattached, and the bolt should be tightened to secure it.
  • Use battery anti-corrosive protection gel or protective felt washers on both terminals before joining the terminals back together. When installing a new battery, always start with the positive cable.

Make sure the connector is firmly pressed against the terminal. Secure the bolt. The negative connector should be connected back to the negative terminal. Now shut the hood and start your engine.

How Often Do Car Batteries Need to be Replaced? 

A battery has a limited lifespan. The conventional thinking is that you should replace your car battery every three years, but you may need to replace it sooner. Your battery may need to be replaced sooner due to factors including your driving style and temperature. 

To ensure that the new battery lasts as long as possible, you must still take diligent care of the old one.

How to Increase the Longevity of Your Car Battery?

Getting into routine battery maintenance has a big impact on the runtime of your battery. Car batteries last three to five years. Regular maintenance is essential if you don’t want to replace yours after just one or two years of use.

Let’s look at what you should do to maintain the battery going for as long as possible-

Invest in A Charger

A dead battery is a total nightmare for any driver. That is why you need a good charger to keep your battery charged at all times.

Purchasing a charger with built-in capability for both servicing and repair, such as the MXS 5.0 from CTEK, is a wise decision. You may also retrain your battery and eliminate sulphation with the breakthrough technology of this battery charger.

Test Battery Voltage

A battery failure could be prevented if you test your batteries in advance. Professional mechanics can perform a battery test for you. However, if you want  you can do a test at home with a voltmeter can come in helpful.

The most user-friendly voltmeters are digital. Execute the voltage test at least 12 hours after your vehicle has been shut off. This will give you the most accurate reading.

A battery with a full charge will have a reading of 12.4 up to 12.8. A mechanic should probably check your battery if your voltage reading decreases from these ranges.

Don’t Idle the Car

If your car remains idle for an extended period of time, the battery won’t have sufficient time to recuperate. Short drives can be just as harmful too. If you drive your car frequently, it will operate at its peak. 

If you can go for a 30-minute drive in your automobile once every week. This will circulate your car’s fluids and warm up the engine.

Clean the Battery 

A car battery may experience a short circuit due to grime, debris, or moisture on the battery. Your battery can eventually be discharged as a result. A sponge and a clean towel work well for removing this exterior filth. 

In order to prevent buildup, do this at least once each month.

Battery terminal and lead clamp corrosion is a regular occurrence. Electricity flow can be impeded by corroded lead clamps and terminals. Therefore, it’s essential to remove any dirt to guarantee the durability and effectiveness of your battery. 

During servicing, ask your mechanic to clean the terminals as well.

Get Car Serviced 

It’s best to have a professional evaluate your car battery to lower the possibility of an accidental breakdown. Ask the technician to check that your battery is functioning properly and is being charged.

Don’t Use Electronic Accessories with an off Engine

It is harmful to the battery to leave interior lights and headlights on. At the same time turning the ignition on to use the touchscreen is also very harmful. 

This is due to the fact that when the engine is shut off, the alternator in your car is switched off. Therefore, electrical accessories use up the battery power in your car.

Make it a practice to turn off everything each time you leave the car. Also, make sure you have locked your car.  This serves more than simply security concerns. 

Leaving your automobile open could result in the computer system still being active. This will be draining your battery without you realizing it.


What Causes My Car to be Dead Every Morning?

Your battery may discharge if the diode in your alternator is faulty. Even when the engine is off, the circuit can still charge if the alternator diode fails. And your battery is dead every time.

How Long Does A Car Battery Take to Fully Recharge?

Most cars roughly 30 minutes of highway drive to fully recharge the battery. Do not forget that the average wait time is 30 minutes. If your battery is nearly empty, the amount of time it takes to recharge may increase.

What Causes A Car’s Battery to Discharge When It is Not in Use?

Interior lighting, door lights, and even defective relays can deplete a car’s battery even while it is not in use. The alternator charges up the battery as your engine is running. This is why blasting the radio or lights coming on is not a worry when the engine is running. 

Ends Words

That was our take on will emergency lights kill battery. As long as emergency lights don’t reach the aforementioned kill voltage they won’t be doing any major damage. But it will definitely discharge your battery.

Hopefully, our discussion cleared all the confusion you had regarding this. Comment down below if you have any other queries.

Until next time!