How Long Before Car Battery Dies with Radio On?

You're parked and all ready to go to sleep but you want to leave the radio on all the night. How long will it run before draining the battery? Let's find out!

For a lot of people, one of their favorite accessories in their vehicle will always be their radio or stereo system. Driving can get pretty darn dull and tedious, and having them classic tunes blaring can certainly make long drives go by quicker.

What about during the times where you want to run the radio without the engine running? How long before your car battery dies with the radio on?

A very interesting question but know this, if you were to, theoretically, leave the radio on in your vehicle with the engine off to see how long it would run, it would eventually drain the battery completely.

When the engine is off, the alternator isn’t running to recharge the battery. This isn’t an issue with the engine running as the alternator will be converting chemical energy to electrical energy to recharge the battery.

So, with that now being understood, how long before car battery dies with radio on? It would probably take a while, let’s just say that, but there are dynamic factors that’ll change the time from one car to the next.

How much electricity does a car radio use?

Image credits: Adobe Stock

Before we get straight to the main event, so to speak, it’s important to address and answer this question first. Knowing how much electricity or power a car radio is going to require will help to figure out how quickly it’s going to drain the battery in your car.

Yet, as with the headline question, this question is also tough to answer as it’s going to depend on the complexity of the stereo system.

From their size to whether or not they’re analog or digital (and also taking into consideration add-on accessories such as a subwoofer), different car stereos and their accessories will drain car batteries quicker than others.

To just give a rough idea, though, expect larger digital radios to use up to five watts per hour, while smaller AM/FM radios will probably only use around one watt per hour. In other words, even the beefier and more complex setups still won’t use a ton of power.

How long before the car battery dies with the radio on?

Alright, so you already know that the battery in your car will provide power to certain elements of your car (such as your radio). You now also know that running just the radio isn’t going to have a huge impact when it comes to requiring too much juice.

So, it’s time for us to finally answer the question you all came here to have addressed.

Again, remember that many additional factors will come into play. Let’s say you have a newer car, and the battery is in really good shape. In this example, you could probably run the radio for a good 10 to 15 hours before draining the battery.

Take a much older car with a battery that has seen better days, however, and you’re probably not going to want to spend too long sitting with the radio on in it with the engine off.

In all honesty, there are several other accessories in your car that are going to be more likely to drain your battery than the radio.

Yet, for whatever reason that you’ll need to rest in your car for a long time, it’s still probably best to bring a portable radio that relies on its own portable battery source.

Better safe than sorry, right?

What are some other factors that can drain your battery?

Image credits: CarCareHunt

While we’re sure you came here for the sole purpose of learning the answer to the question “how long before car battery dies with radio on”, we also thought it’d be beneficial to educate everyone on some of the other factors that can drain a car’s battery with the engine off.

Of course, we’re not taking credit for the information here as we’re pretty much just relaying the advice that Firestone Complete Auto Care provides.

It’s excellent stuff for sure and the next time you’re wondering why your battery ends up drained of juice, it could be because of any of the following.

Too many short trips

While just taking short trips may seem like an effective way to not “overuse” your vehicle, it’s actually not healthy for a car. Part of the reason why is when you take short trips, you might not be giving the alternator enough time to recharge the battery. This is even worse if you have an old battery and, in general, this practice can shorten the lifespan of your battery.

Leaving your headlights on

Here’s the good news. If you drive a newer vehicle then there’s a good chance that it’s designed to turn off your headlights after a certain amount of time has passed. Without this feature, though, leaving your headlights on after the engine has been shut off can be problematic if you don’t realize it right away.

The fact that it’s too old

It’d be nice if your car battery would last as long as your car, but that just isn’t going to happen. Some batteries can last up to five years but if you know you’ve had your battery for many years, it may be getting time for a replacement.

There are many more than this and, again, you can check out all the factors from Firestone Complete Auto Care.

Final thoughts

How long before car battery dies with radio on? More than likely, you’re not going to be sitting in your vehicle long enough for the radio to fully deplete the battery.

Unless, of course, your car and battery are old.

You might also be interested in our other article covering Depth of Discharge (DOD) of lithium batteries and whether or not you should upgrade your car’s battery.

For short bursts where you want to listen to the radio maybe for an hour or something, though, there shouldn’t be any issues with most vehicles. Simple enough stuff, right?

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Tyler Jones

Tyler is much like a swiss knife. Even though he has a degree in Computer Science, he knows almost everything there is to know about camping. He has been writing for HeadlessNomad since 2021 and has contributed with over 100 articles. If you have an outdoor-related question, then Tyler much likely knows the answer.