How do I know if my battery is dying?

My radio shuts down when I just have the key turned to accessory? Then audio shut down due to low battery is displayed on dash.

My car has 80000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
Hi There,
It sounds like you may have a weak battery that may need to be replaced. This can be verified by having one of our mechanics come to your location to test your battery’s strength to determine whether or not it is capable of being recharged. You may also have an alternator that is not properly charging your battery as well which may contribute to the battery dying prematurely. I would suggest having a professional from YourMechanic come to your location to diagnose and inspect your charging system.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

2013 Ford Focus batteries usually last between 3-5 years, but this is variable depending on driving habits, weather conditions, the type of battery, and more.
The most accepted symptoms of bad 2012 Ford Focus batteries are if your car is slow to start after turning the key, or if your battery cables and connectors show signs of considerable corrosion.
What is draining my Ford Focus battery? The most common cause of a battery drain in any vehicle is a parasitic draw. This is an electrical current that is being drawn from the battery even when the car is turned off.
Thankfully, Ford completely revamped the Focus last year, bringing about a much-improved interior, higher fuel economy and new features. As such, the 2013 Ford Focus stands as one of the best small cars you can buy.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Battery dies if the car sat for over 20 hours
ANSWER : Batteries that drain overnight are common. Usually when this occurs, there is a parasitic drain on one of the car’s systems. When this occurs it drains the battery down over time. Batteries that are drained down repeatedly can cause them to fail. The most common causes of the battery drain are aftermarket accessories, radio, power windows and seat motors. If you can find the cause of the parasitic drain, a certified mobile technician from YourMechanic can come to your car’s location to diagnose your battery and determine what should be done.

My battery light is on.
ANSWER : The problem is not the battery, but the charging system is not keeping the battery recharged. The alternator is the most common cause of this, though failing battery cables can also be a cause. I would recommend having the battery cables and alternator tested and checked by a mechanic, like one from YourMechanic, who will come to you and diagnose the problem for you. Do not try and drive it or it will leave you stranded from the battery going dead again. The cables to the battery from the alternator may be bad or the alternator is not charging. Only the testing and diagnosis will reveal the problem.

Battery Keeps Dying
ANSWER : There are three possibilities, to start with: 1) there is a voltage drop in the wiring between the alternator and the battery; 2) the "parasitic" power draw occurs while the car is running, not so much while it is off, thus overwhelming the alternator and consequently the battery is not being fully re-charged; 3) there is a parasitic power draw when the car is off but to pick it up requires data logging. With regard to these possibilities, if you desire that the required diagnostic steps be performed by a certified mechanic, please simply request an electrical circuit/charging system diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Battery keeps dying for no apparent reason
ANSWER : Hello. If the battery and alternator are fine then I would test the ignition switch. It will commonly stay on and cause this. If it is fine, then an amperage draw test needs to be done on the vehicle. If all of the electronics are stock, then the issue may be a sticking relay. I have had the main fuse box fail internally and cause this a few times on this vehicle and the amperage draw test will identify this as the issue. If you need to have this looked at, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose your battery.

Car battery dying quickly especially after longer driving
ANSWER : It sounds like the alternator is not charging the battery, when are you driving long distances. Running all the accessories and then shutting it off can cause the battery to be too weak to restart the car. If the alternator is intermittently not charging, then you may have other wiring issues or just an intermittent problem within the alternator. Have the charging system checked by a mechanic after driving it and not shutting it off, to see if the battery is being charged. You may also have a body control module issue with extended storage mode. The dealer can check this mode with the special scanner and checking the extended storage fuse is not installed.

Has new alternator, new battery when started , motor dies when battery is disconnected…my mechanics are stumped on this
ANSWER : Hello.

If replacing those particular components did not correct the issue then the next thing I would look at is the vehicle’s voltage regulator. It appears that this engine’s electrical system is equipped with an external voltage regulator that functions, or malfunctions, independently of the alternator. The voltage regulator regulates power from the vehicle’s alternator, and can cause issues with the electrical system when it malfunctions. I would test it to see if it is functioning properly. It is a silver box that should be mounted somewhere in the engine bay, usually on a wheel well. A technician from YourMechanic can come to your home or office to replace your car’s voltage regulator if necessary.

Regards,
Eduardo

Battery light stays on and overnight battery drain. 2006 Land Rover LR3
ANSWER : Hello – this problem can be diagnosed by connecting an ammeter to the positive (red) battery cable, observe the current drain (likely less than 1 amp), then, one at a time, remove each fuse, check to see if the current drain has dropped to near 0, then reinsert the fuse. This process should identify the faulty circuit in most cases. The specific components on that circuit can then be checked for current drain problems. A professional mechanic, like YourMechanic, can come to your location, and perform this procedure for you, and identify, replace or repair the failing component.

Battery light stays on and overnight battery drain. 2006 Land Rover LR3
ANSWER : Hi there – yes, something is going on here that’s draining your battery. Perhaps the pressure of the engine wash dislodged wiring which has shorted, or there was a chemical reaction to the cleaning solution that caused electrical damage in the alternator or voltage regulator. These componnents can be checked off of the vehicle. Vehicle wiring can be diagnosed by connecting an ammeter to the positive (red) battery cable, observe the current drain (likely less than 1 amp), then, one at a time, remove each fuse, check to see if the current drain has dropped to near 0, then reinsert the fuse. This process should identify the faulty circuit in most cases. The specific components on that circuit can then be checked for current drain problems. A professional mechanic, like YourMechanic, can come to your location, and perform this procedure for you, and replace/repair the failing component.