Will FM Transmitter Drain A Car Battery?

FM transmitter is used to broadcast signal coming from a portable device like mobile phones or MP3s using the standard FM radio. It is popularly used nowadays for a car stereo that does not have auxiliary jacks for phones or MP3. The big question is if this device will use up a lot of the car battery’s power and eventually drain it out.

Will an FM transmitter drain a car battery? Most modern cars have the 12V socket which turns off when you turn the engine off also. So there is no need to be worried about draining your battery supposing you have left your FM transmitter plugged in.

The FM transmitter does not draw that much power against your battery. If you know that your battery is in a good state and has a durable power or energy, it will never drain that quickly.

Cars or vehicles which are not using a digital stereo with USB and monitor usually end up using an FM transmitter to be able to play external music from their phones, iPhones or MP3s without changing the entire audio system of the vehicle. FM transmitter uses minimal energy or power that would make it impossible to drain the battery.

Will Leaving the Plugged-in Gadget in Your Vehicle Put the Battery Dead?

Some FM transmitters have an off and on a button. It also depends on the car model where you used it. When the car engine is off, it may still draw small power or energy because you can always use the transmitter even the engine is off.

It might again draw power from it, but it is not enough to drain the battery even if you leave it plugged in over the weekend. However, if you have doubts about it, you can unplug your FM transmitter to make sure that it will not draw power from your battery and drain it eventually.

Other Gadgets that Can Kill Your Car Battery aside from the FM Transmitter

We often suspect that an FM transmitter will draw out the power out of your battery. Generally speaking, if it is just the FM transmitter alone, we cannot wholeheartedly say that it can be the culprit for your dead battery. Some other gadgets can also make your battery dead. Here are some of them:

Car Alarms

It is one of the most notorious power suckers of a car battery. Not even the healthiest kind of cell would ever survive the power drain brought about by the car alarms. If you have your car alarms installed by non-dealers, you should be able to check it twice. Most battery drain problems come from the poorly connected electrical system of the signal. Car alarms installed by the car dealers or manufacturers themselves tend to be less of an issue.

However, the cheaper ones mostly have problems. The installation which is done after sales, usually makes use of non-standard wiring techniques. Poorly installed car alarms create electrical problems which tend to develop parasitic drain to your battery. To avoid this, bring your car to a trusted car electrician.


Typically, the OEM stereo doesn’t give any problem to the battery at all. However, the moment you changed the audio system for your vehicle, that is also the time where the problem begins.

Some car owners modify their sound system by setting up prominent speakers who are then connected directly to the battery. When you do this, you are bypassing the electrical system of your vehicle, which will then go to the stand by mode.

It is the head unit which will signal them to turn on. Under the standby mode, they will draw only three or just a milliamp. Once they failed to go in standby mode, the switches will register incorrectly and will bring as many hundreds of milliamps, though they are not working or making any sound at all.

Remote Controlled Keys

A radio receiver is used to listen for the frequency of the keys continually. When the receiver receives the signal with the rate assigned to it, it automatically turns on to check if the keys are the match for your car. It could bring some severe issue if you have left your car parked for a couple of weeks without starting the engine.

This issue is the problem with proximity keys. Every time that a similar key walks by, that makes it startled and alerts the frequency. It will soon drain your battery for several minutes and will quickly kill your battery.

My FM Transmitter Got Stuck in My Cigarette Adapter, Will it Make My Battery Dead?

I had this question with one FM transmitter user. The car owner is afraid that it might deplete his battery since he cannot pull the transmitter out. Honestly, the FM transmitter adapter will not ruin your car’s charge, especially if the battery is in good condition.

However, if you are unaware of the electrical problems of your vehicle, then leaving your transmitter stuck in your cigarette adapter might add up to the problem.
The best thing you can do is to find an expert who can pull the thing out. It will bring you peace of mind knowing that your FM transmitter will not be a cause of parasitic drain to your battery and eventually leaving it dead sooner or later.

How Long Can I Run My Car Stereo or FM Transmitter before My Battery Gets Drained?

We need to make a lot of assumptions before we can conclude the number of hours before you get your battery dead. Supposing your battery is under these conditions:

1. It is new and in good condition. You will have about 600 Watt per hour if your battery is 12V used for an average sized car.
2. No other accessories are running on the vehicle.
3. You are still using the OEM stereo and no modifications yet.
4. You considerably play loud music but not loud enough to bother the entire neighborhood.

Under these circumstances, your car audio will typically draw around 50W. To drain your battery, you need to use it for 10 hours continuously and up to a maximum 12 hours of use.

Of course, this will vary if your battery’s capacity is more significant and more substantial. The higher capacity your battery has, the longer time you can use your audio system before you can drain it out.

Does Listening to the Radio Using My FM Transmitter without Starting the Car Engine? Will it Turn My Battery Dead?

Yes, you can listen to your radio without turning the engine on. However, in doing so, you might be turning on other accessories as well, which could be the reason for drawing the power out of your car battery. The radio itself doesn’t cause too much power drain on the battery.

However, prolonged use without recharging it will eventually kill your battery. Another thing is if your battery is already scheduled for replacement, using the radio transmitter without turning the engine on will kill your battery.

The question of whether the FM Transmitter drains a car battery depends on many aspects and circumstances. You need to know if your battery is still running well before you opt to leave or use your radio and FM Transmitter. Many factors should be considered in this situation.

1. Will my FM Transmitter drain my car’s battery if I leave it plugged in? – Yahoo Answers
2. Would the fm transmitter I bought drain my car battery? – reddit
3. Does leaving phone chargers plugged in a car overnight deplete the car’s battery? – Quora
4. How To Diagnose a Dead Car Battery – POPULAR MECHANICS