How Long Does a Car Battery Last with the Radio On?

With the radio on, you can kill your boredom while waiting for a friend, in traffic, or when you deliberately decide to sit and relax in your car. Unarguably, a car radio is an indispensable car component. 

However, what is responsible for powering it while it plays? If you were driving, the car radio would directly tap the electric current from the engine. But when the engine is not functioning, it relies on the car battery. 

The alternator keeps the battery charged when the engine is running. It also powers other functions such as running your car stereo, supporting the air conditioning unit, the windscreen wiper, lighting systems, among many others. 

So how long does a car battery last with the radio on? It depends on the strength of your battery, the additional features you run alongside, and your car’s accessory accommodations. But the average time a car battery lasts with the radio on is four to ten hours. 

How many amps does a car stereo use? 

The battery capacity is measured in diverse ways, including cold-cranking amps. It is estimated at a temperature of 32°F; this is because a cold temperature significantly affects how fast a battery will lose its charge. In thirty seconds, your battery can release seven amps at a cold temperature, which means the battery capacity reduces. 

In that case, your stereo will drain the battery much faster. 

Turning on your vehicle multimedia service alone can drain a significant portion of your battery. For instance, if you have a 200-watt vehicle stereo system, it can consume somewhere between 20 to 25 amps. 

Typically, the engine continues to power the radio from here. Since it utilizes a direct energy source, there will be no strain on your battery. The lost amperage will also be replenished if you leave the car running long enough to recharge it.

car radio

However, when you use the radio without turning on the ignition, it will continue to run on the battery. The average car battery has between 550 to 1000 amps. Most cars also have a rating of 50 Ah. If your multimedia service consumes about five amps per hour, then you can use your radio for four to ten hours before it needs another full charge. 

Ideally, modern car stereos have been designed to consume less battery when you use them without the engine is not running. But if you use it with a speaker, amplifier, or aux cord, the battery will reduce much faster. But again, this also depends on the vehicle’s newness and the accessories connected to the stereo. 

Let us break it down. With a subwoofer, your stereo will undoubtedly consume more energy. The energy consumption can take as much as an hour or two off the car battery’s charge. If there is an additional function like turning on the lights in your automobile, then the battery will drain even faster. 

An absorbent glass mat (AGM) battery has been designed to work more efficiently even when using your car’s multimedia services. This is the battery option that most modern vehicles are designed with. 

How long can you leave a car stereo on?

Typically, a car radio does not consume much battery if you turn it on while the engine runs. But leaving it on without turning on the ignition is another matter. It will drain the battery after a while. 

Again, the average car stereo consumes about five amps, which will undoubtedly be exceeded when you turn up the volume. When you combine other features like your aux cord, Bluetooth, or an amplifier, you can expect the radio to consume more battery. 

How long can I leave accessory mode running? 

Modern cars are designed with an exceptional feature called the “accessory mode.” Here, you only need to turn the ignition up a notch before you can access features like your stereo, air conditioning, and navigation system. 

Previously, the car had to be running while these features function. But now, most cars will allow them to work for about twenty minutes before they go off. You can also take charge of how long the accessory mode runs, but we recommend thirty times forty-five minutes to avoid putting too much pressure on your car battery. 

How to use your radio without killing your car battery 

If you are taking a long trip, your car radio is an excellent entertainment source. Using it will not affect your car battery because the alternator powers it when you turn on the ignition. 

So, ensure your car battery is fully charged before you turn on the radio. Furthermore, keep the ignition running to ensure the radio keeps tapping its current directly from the alternator and not your car battery. 

In a situation where you are merely waiting for someone or are stuck in traffic, your car stereo can run without the engine running alongside. But the trick is to avoid using it for too long. 

You need at least 130 amps to start your engine, which means your car battery needs about 150 to avoid disappointing you. The average car battery has about 550 amps, so you must ensure that your car radio does not consume more than 300 amps. This is the safest bet. 

Bottom line 

The urge to crank up the radio while taking a long or short ride is sometimes irresistible. So is tuning to your favorite station or slotting a playlist of your favorite songs into the stereo while waiting or passing idle time.  

What we will tell you, though, is that leaving your radio on without turning on the ignition will drain your car battery. Of course, it will not be immediate, but depending on the production period of your automobile, the battery may run flat in less than ten hours. 

When you are leaving your car, it is vital to remember to turn off the radio. While it may be uncommon to leave this entertainment device working for ten hours, it is pretty prevalent to forget to turn it off. You will often meet a completely dead car battery when you realize this mistake. 

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