How Long Before Car Battery Dies With the Radio On

We have all found ourselves in a situation where we wanted to entertain ourselves with music in our car while waiting for someone, camping, or even while waiting for a service truck by the side of the road. But naturally, the radio will drain the car battery after a while, perhaps leaving you in a worse situation than you are already in, but just how long do you have before that happens?

Answering how long it takes before a car battery dies with the radio on is fairly difficult. That answer depends on a lot of factors, such as radio volume, the number of speakers, whether or not you have an amplifier, battery health, etc. So, the answer would be anywhere between 3 and 12 hours, with the average being around six before you can’t crank the engine.

how long before car battery dies with radio on

How Does the Radio Drain Your Car Battery

Your car’s engine and all its electronics rely on the battery for power. That means starting the engine, running the lights, radio, AC, heat warmers, etc. And the reason you don’t have to recharge a car battery like you do any other is that cars have a built-in generator (alternator) that charges the battery while the engine is running.

The alternator makes enough current to charge the battery pretty quickly back to full after you crank the engine to start it. Alongside charging the battery, the alternator also makes enough current to power all the electric auxiliaries, like the radio. So, whenever you are driving the car, the battery is being recharged, and all the electrics can run indefinitely as long as the engine is running.

However, when you turn the radio on or any other auxiliary, like the lights, while the engine is off, they are drawing power from the battery like any other remote device like smartphones, wireless earbuds, or laptops.

And, of course, keep running any electric device on a battery, or a radio in this case, without charging it (running the engine), and it will deplete the battery eventually. On the other hand, while you are driving, the radio cannot drain the battery provided the battery and the charging system are healthy.

Can Your Car Battery Die if the Radio Is On

We have already established that a car radio can drain the battery when the engine is not running. So, here we will address the question of whether or not a radio can drain the battery so much that the battery gets damaged or destroyed. And the short answer to that question is yes.

Unlike lithium-ion batteries, which we can find in smartphones, laptops, or even electric cars, the lead acid batteries in cars are not meant to be discharged to less than 80%. And while it’s true that you can recharge them after they are drained, the life of that battery can decrease by as much as 40%.

And, of course, the radio has no problem draining the battery to less than 10℅. Now, if you have a reasonably new and healthy battery, the first time you drain it, you probably won’t make such a big problem. However, recharging the battery as soon as possible is crucial to prevent damage.

On the other hand, if the battery is more than two to three years old, draining it overnight with a radio is almost guaranteed to destroy it. That means you most likely won’t be able to charge it up because it doesn’t hold any charge. But even if you manage to charge it, the battery will probably be losing charge over time, leading you to believe your car has a parasitic drain. Moreover, the battery could behave normally afterward but randomly refuse to crank the engine. But whichever of these cases you potentially encounter, you will end up having to replace the battery. 

How Long Before Car Battery Dies With the Radio On

In order for a car radio to kill the battery by draining it, you would have to leave the radio running for a significantly longer period than it takes to drain it to the point where it still has charge but not enough to crank the engine. But how long before the car battery dies with the radio on exactly is hard to tell.

If we assume that it takes about 6 hours on average to drain the battery enough so that you can’t start the engine, let’s say that it takes about 10 hours on average to destroy the battery. Again, that time period depends on a lot of factors, so we would advise you not to rely on the 10-hour assumption.

That said, leaving the radio on for 10 hours, even if it doesn’t destroy the battery, will more likely than not cause some significant damage. And while you can minimize that damage by charging it immediately after, you can’t prevent it. Moreover, the ten-hour period that it took the battery to drain will most likely be enough to damage it.

will my car battery die if i leave my radio on

How Long Can You Play the Car Radio Without Draining the Battery

There are far too many variables in determining how long it takes a car radio to drain the battery. But judging from my and other people’s experiences, it takes about 8 hours for the radio to drain the battery if you play it on low volume. That’s also with the assumption that the battery is healthy and fully charged and that the car doesn’t have a big amplifier or a sub-woofer.

However, if you have an old battery and are blasting music at nearly full volume, the battery can drain in as little as two hours. Then there is sound system power. An 800W system will consume much more current than a 200W system will, even at low volume.

Next, amplifiers consume about 150 to 200 watts regardless of volume, and if you have a subwoofer, that’s another 400W at least. So, it’s easy to see just how much the sound system power can vary and how much difference it can make.

Furthermore, the size of your battery is also extremely important. For example, a 45 ampere-hour battery will drain twice as quickly, powering the same sound system as a 95 ampere-hour battery will. Moreover, some cars have two batteries, the main one and the auxiliary one, which adds a whole new dimension to our equation.

Next, the type of radio can make a significant difference, too, if we take into account that some radios have an inch-long screen while others can be up to 8 or 9 inches. Moreover, the source of the music you are playing will make a difference too.

For example, playing AM/FM radio will consume much less power than listening to a CD. The CD has to engage an electric motor and the laser reader to play, while a radio antenna or a Bluetooth module doesn’t need almost anything other than the radio screen and speakers. And lastly, the speaker volume plays a huge role. A radio that’s set to full volume will consume 80% more power than it would at 10-15% volume.

But to simplify things to some extent, if you are sitting in your car with a good battery, you can spend the night in it with the radio on at 10 to 15 percent volume. Not to mention you can wait for someone for an hour and listen to music without any problems whatsoever. But if you are blasting music at full volume, someone will need to help you push-start the car after two hours.

How Do I Keep My Car Battery From Draining When Not in Use

If you are wondering how to listen to the radio without draining the car battery, there is no possible solution; the battery will drain inevitably. However, if you are storing your car for a month or longer, there are a couple of ways you can prevent it from draining, even though there is no way of telling how long before the car battery dies without driving.

The first and best solution is to buy a car battery trickle charger. Trickle chargers are designed specifically for the purpose of keeping the car battery charged over a long time period without being used. Furthermore, they improve the battery’s health and make it last longer. The good news here is that you can find them on Amazon for around 20 bucks, and the bad news is that they need a power outlet to work.

In case you don’t have access to a power outlet where the car is stored, disconnecting the negative battery cable will help preserve some charge. In any case, it will help retain the charge longer by at least a week or two.

Furthermore, if you live in a cold climate and want to store the car during winter, instead of disconnecting the battery, it’s better to remove it from the car. Then, you should store it someplace warmer, like somewhere in your house where it won’t get in your way or anywhere warmer than outside.

Final Words

Ultimately, the best guess we can provide, taking all aspects into account at average value, is that it will take around 6 to 8 eight hours for the radio to drain the car battery to the point where you can’t start the engine again. However, with a smaller and older battery plus a powerful sound system, that time can be as low as two hours. On the other hand, with a bigger battery and a less powerful sound system, it can take up to ten or even twelve hours.

Ibro Cehic

Ever since I was bitten by the automotive bug during early childhood I was obsessed with cars. My first driving experience came when I was ten and I already started tinkering with cars and motorcycles at thirteen. So, right from the beginning, I knew my life would revolve around cars, even if I wasn’t sure how that would happen. And today, thanks to my second passion, writing, I get to share my love for automobiles with other enthusiasts through my articles.

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