We’ve all been there. You park up at home, turn off the car engine and your favourite song comes on. You want to listen to it all, but you’re a big fan of Pink Floyd and Echoes just started playing, in all its 23-and-a-half minute long glory.
Now, you can’t fully embrace the music because you’re worried about the power that your radio is syphoning from the car’s battery just to belt out your tunes. Well, worry no longer, because Scrap Car Comparison is on hand to explain just how long the average car can last with the engine off and radio on before the battery gives out and you’re marooned on your driveway.
How Does the Radio Drain the Car Battery?
Despite what your aunt’s Nissan Micra’s bumper sticker tells us, car radios aren’t ‘powered by pixie dust’ and do, unsurprisingly, require electricity. Naturally, the best source of this power inside a car is the battery that’s sitting under the bonnet.
So, when you press the ‘on’ button and the DJ starts playing their songs, it’s actually your car battery that’s giving it life. This same battery is used to power absolutely everything in your car. In fact, it’s even crucial in starting the engine and getting the car going at all. As the radio plays, it draws power from the battery, meaning that it’s possible for your car battery to die while listening to the radio. You probably won’t need to remove or replace the battery, but it still puts you in a tricky position.
You probably already know that, which is why you’re wondering just how long the radio can run for before. As it turns out, there’s no set figure, but there are numerous factors that can affect just how much juice your battery pumps into your car radio. You’ll want to know them all to ensure you don’t end up with a flat battery.
Will a Car Radio Work if the Battery is Dead?
No, without a working battery, the radio simply will not function. A total lack of power will leave you in complete silence. As we mentioned before, you won’t even have the roar of the engine to keep you entertained. Maybe now would be a good time to see if your aunt can spare some pixie dust…
How Long Will it Take For a Car Radio to Drain the Battery?
The radio itself doesn’t use an awful lot of power, so it’s very unlikely that you’re going to end up with a dead battery from one listening session. On average, a regular car battery that’s powering a regular car radio will generally keep going for a whopping 10 to 12 hours. That should be plenty of time for you to listen to whatever you want, even an entire audiobook!
Things become a little more difficult to predict when you factor in the many variables that can change the amount of power required to make your sound system work as intended. If you have aftermarket sound equipment, like subwoofers, they will drain your power much more quickly. Similarly, if you like your music loud, turning it up to 11 will have some effect on your battery’s power consumption. Combine those two things and you could be looking at a car radio that’s draining your battery at a much faster rate, giving you a listening time of only a few hours.
How to Use a Car Radio Without Draining the Battery
If you’re still concerned about using your radio, perhaps because your car battery isn’t what it used to be, or maybe because you do use a more powerful aftermarket sound system, then you’ll need to know how to minimise the amount of power your music maker uses.
Many modern cars come with LCD screens built in, through which you can control the radio station or other audio source, or set up other things like satellite navigation or the ability to make hands-free phone calls. If you’re lucky enough to own a Tesla, you’ll even be able to play video games on your car screen. However, all of this is using up power. If you’re sitting idle with the engine off, it’s best to prioritise one thing. Shut off the maps and games and use the radio. Take a look through the settings too, as you may find options to turn off certain elements individually, which will save you power.
Besides a built-in screen, other features that will drain excess power can include the interior lights, fans and heaters. Again, it’s about choosing what you want to prioritise if you’re trying to keep the power usage down to an absolute minimum. That being said, each of those features will use a paltry amount of power, so don’t worry too much if you do use them together.
What To Do If Your Car Radio Has Drained Your Battery
Let’s say you’ve accidentally left your car radio on all night. You’ve woken up to find that your car battery is dead and the vehicle is going nowhere. What’s your next move to get it up and running again?
The most common way of reviving a dead car battery is through a process known as jump-starting. This is the motoring equivalent of taking a set of defibrillators to its heart and giving it a burst of power. To jump-start a car you’ll need a set of jump leads and… another car.
That’s because a jump-start shares the power directly from one car’s battery with yours, giving it a charge that’ll get the engine running again without killing off the car you’re getting the power from. Perhaps it’s less comparable to using defibrillators and actually the vehicular answer to CPR?
If you’ve never used a set of jump leads before, here’s what you need to do to safely bring your car battery back to life:
- Firstly, don’t attempt to jump-start an electric vehicle or hybrid car, as this can cause more serious damage.
- Park both cars either nose-to-nose or side-by-side, but without them touching. They need to be close enough for the leads to reach between them both.
Keep the handbrakes on and ignitions off.
- Connect the red jump lead to the positive (+) terminal on both car’s batteries.
- Connect the black jump lead to the negative (-) terminal on the working battery.
Attach the black jump lead to an earthing point on the dead car, away from the battery and fuel system.
An earthing point will be an unpainted, bolted-on metal part attached to the car chassis or engine block.
- Wait for a few minutes, then turn on the working car. Let it run for a minute.
- Turn on the car with the flat battery.
- Leave both cars idle for ten minutes.
- Turn off both cars.
Disconnect the leads in reverse order. So, remove the black lead first (starting with the earthing point) and the red lead second.
Make sure that the leads don’t touch each other or the cars as you remove them.
- Start the dead car, which should now be working as normal.
If you don’t have access to jump leads or a second car, there are less reliable alternatives that you could try to get the car up and running.
If you drive a car with manual transmission, it is possible (albeit a bit dangerous) to ‘bump start’ your car. This doesn’t require a second car, or jump leads. It only requires the power of friendship.
- Get some of your mates to gather behind the car.
- Switch off everything that might drain any amount of power, like those that we’ve listed above.
- With the clutch down, take off the handbrake and get your friends to start pushing your car.
- Once it’s rolling at around 5-10mph, turn the key in the ignition to the final point before the engine starts.
- Release the clutch.
If you turn the key a few times and the car feels like it’s going to start, keep trying until it does. If it gets there, drive the car for an hour or two and the battery will start to recharge.
Finally, the most creative way to try and restart a car with a flat battery involves using Epsom salt and distilled water. It’s an incredibly long, complex and potentially dangerous process, so if you choose to go down this route, make sure you know exactly what you’re doing. WrightGrid has an extensive guide explaining this procedure in great detail.
If you’ve tried everything to get your car going again, or the battery just doesn’t seem to last long enough for your car park jamming sessions, it might be time for a new ride. Scrap Car Comparison can get you the best prices for selling your car in just 30 seconds, and our expert scrap buyers will even collect your vehicle nationwide at no extra cost. Take a look at our long list of locations and use Scrap Car Comparison to arrange the sale of your car for scrap or salvage today.