Battery runs down after car is idle

Battery runs down after car is idle.
Experienced mechanics share their insights in answering this question :
Hi there! Your problem sounds like an issue with your charging system; more specifically, the alternator.

The alternator is a major component in the charging system whose job is to maintain the battery charge during vehicle operation. Something as simple as a blown fuse could impede the alternator’s function, or the issue could be more complex.

I would suggest having an experienced mechanic, like the ones at YourMechanic, inspect the entire charging system to pinpoint the issue and suggest appropriate repairs.

How to Identify and Fix Common car Problems ?

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

If your Jeep keeps dying, it is likely due to a failing alternator. The alternator is what charges the battery and provides power to the electrical system when the engine is running. If it fails, the battery will eventually run out of power and the Jeep will die.
Your apps still run background processes while your phone is idle. Idle does not mean off. Even with your phone off, powering it back on will use up battery. Every function of your phone requires power and that power will drain the battery to some degree.
Electrical devices or lights left running, a defective charging system or alternator, and extreme weather are some common reasons but maybe it`s just time to get a new battery.”
Your car battery can drain over time from stereo components (subwoofers), phone chargers, and anything you leave plugged into vehicle outlets that continue to draw power from the battery after the car is turned off. Other power drains include interior and below-vehicle LED lights. Loose or corroded connections.
Using a test switch and digital ammeter is the simplest, most accurate way to measure parasitic drain directly. A test switch goes between the negative battery terminal and negative battery cable.
The most common causes of excessive parasitic drain include faulty relay switches, malfunctioning alternators, damaged wiring or connections, and electronic devices left connected or powered on when the vehicle is off.
If your car sits idle for extended periods of time, it can slowly lose the charge in its battery. And now, more than ever, it`s essential to make sure it`s charged and ready to power your vehicle the next time you need it.
The ignition relay is essentially an electrical device that works as a switch for the power to the ignition system. Its job is to make sure electricity flows from the battery to the different components that need power. A bad relay will drain your battery and make it difficult to start the ignition.
A corroded or defective alternator diode will faultily continue charging the circuit even when the car off. This, in turn, will drain your car battery and cause the car not to start.
The short answer is: Yes, it can. It could also drain the battery even faster if you repeatedly try to start your car with a faulty starter. A faulty starter is also one of the leading causes of battery overcharging.
While excessive parasitic battery drain is considered a problem, most vehicles contain a “normal” amount of battery drain. Typically, the normal amount of parasitic draw is between 50 and 85 milliamps in newer cars and less than 50 milliamps for older cars.
What Causes a Car Battery to Keep Dying? Some of the most common reasons for a car battery to die repeatedly include loose or corroded battery connections, persistent electrical drains, charging problems, constantly demanding more power than the alternator can provide, and even extreme weather.
To determine the source of Parasitic Draw (Dark Current), start by checking for aftermarket accessories. If any aftermarket accessories are present, remove the power to these accessories, and then retest. Finally, follow normal diagnostic procedures to identify source of draw.
Typically, your car can sit about four weeks to two months without driving before the battery dies. The reason your car can sit only for so long before it dies is the fact that your car battery is in use even when you`re not behind the wheel.
Use Cruise Control: Saves Battery On Flat Roads

Constant driving speed is highly correlated with higher fuel efficiency. This only applies to flat roads, however. On hilly roads cruise control can use more energy. It makes sense, really.

How Long Does It Take To Charge A Car Battery? If you have jump-started your car, it is recommended to let your vehicle run for at least 30 minutes because it would typically require at least half an hour to charge a dead battery entirely or at least sufficiently.
Issues such as faulty wiring, bad fuses or interior lights that fail to shut off will continue to drain your battery while it`s idle.
Symptoms of a burnt out diode:

The engine will begin to run rough, lack power and eventually stall and not start again. The battery warning light will turn on, warning you that there is a problem with your alternator charging system. The headlights will become dim due to reduced battery voltage.

This can be a result of various factors including the number one cause which is leaving headlights, glove box lights, or cabin lights on overnight. Parasitic drain can also be caused by defective fuses, bad wiring, and poor installation of a new car battery.
A: The only way the fuel pump could be draining the battery is if the fuel pump is running full time. And it would drain the battery within a few hours, not a week. A normal car battery has 48-64 ampere-hours of capacity, while a fuel pump draws, depending, 6-10 amps.
Common signs include the engine not starting, inability to stay running for a long time, and the Check Engine Light coming on.
This can be caused by overcharging, undercharging, or leaving the battery in a discharged state for too long. A battery that doesn`t hold a charge is frustrating and can happen for many reasons. It could be an issue with the batteries themselves or a problem with the charging system.
What happens when the battery dies? Can a dead battery stop your car if you`re driving it? Yes, a dead battery will cause your vehicle to function progressively worse until it finally grinds to a halt on the side of the road.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

When changing the car battery, do you "register" the battery to the car computer?
ANSWER : Hi there. Changing the battery has nothing to do with programming a battery. If the car was flat dead with a battery that lost all of the power because the dome light was on, then when jumped the vehicle will run fine. What may need programmed when the battery is replaced is the key fob. The key fob will lose programming to the computer as the vehicle computer is reset. However, if a 9 volt battery saver was put into a cigarette lighter and the car battery was removed, then the computer will not lose its memory and be just fine. If you need further assistance with your battery, then seek out a professional, such as one from Your Mechanic, to help you.

Water was spilled in the trunk which soaked the car battery. Car won’t start now. Does water destroy a car battery?
ANSWER : Hi, thanks for writing in about the concern with the BMW 320i. If the battery was submerged in water then it’s completely possible for the battery to short out and die. Your friend will need to have the battery replaced. Also be sure to get all of the water out of the trunk. Have a certified technician, like one from YourMechanic, help you guys out if you need assistance with replacing the battery. Good luck.

My car will not start Intermittently. I purchased a new battery 2 weeks ago and yesterday the car wouldn’t start. Got a jump and
ANSWER : The issue you are having is probably due to an intermittent fault in the starter motor itself or a deficiency in the starter electrical circuit, for example a large voltage drop due to a poor ground or a high resistance connection. These issues can be readily diagnosed and resolved on a mobile basis if you request a hard starting diagnostic. If you request that diagnostic, the responding certified mechanic will get this resolved for you promptly. Based on Toyota’s Factory Service Manual, the battery should not be disconnected if the vehicle engine is running. The battery acts as a large resistive voltage sink and consequently taking the battery out of the circuit, while the alternator is still running, can create a voltage spike on the car’s electrical system which is not good for voltage sensitive components such as the engine computer. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Replaced alternator on car 2 times each time shows it’s charging 14v let car run for a little bit then test drive and car voltage
ANSWER : There are reports that the replacement alternators will not communicate with the engine computer and will not charge correctly. I recommend using only the manufacturer approved replacement part. It can be new or remanufactured but approved for use in the vehicle. Some lower cost alternators on the aftermarket will have charging problems since they will not communicate with the ECM on the vehicle and will stop charging.

My car wouldn’t start after battery was just replaced my car cd player is running after I turn the car off
ANSWER : Your CD player definitely should not be running after the key is off and out of the car. It will certainly drain your battery. So the good news is you can be reasonably certain about what is killing your battery. I would remove any CD’s from the player and see if it still spins with the key out of the car. If you need to go a step further, you will need to disconnect the power wire to the stereo. It is located at the back of the stereo and this will require some dash disassembly to access the rear of the radio.

You will want to disconnect the stereo overnight to see if the battery dies. A quicker more accurate way of testing for a draw, which is what this is called, is to use an amp meter at the battery to confirm the stereo is the source of the draw. Most multimeters have amp settings that can be used up to a ten amp draw. You will need to connect the leads of the multimeter inline with the positive battery cable. Do not turn the key on while the multimeter is inline with the battery. The current will blow the fuse in the multimeter then you won’t be able to complete the test. Also, you will need to wait somewhere between ten minutes and an hour for all the modules in the car to go to sleep. Modules that are on will draw current until they go to sleep. You are looking for a draw of more than a half of an amp continuous.

With the multimeter connected, disconnect the radio connector and see if the draw goes away. You will see this reflected in the multimeter amperage reading. This draw test can be used to locate any draw that may be occurring. If you find the radio is not the culprit, you should then begin removing fused one at a time to see what is causing the draw. When the draw goes away after removing a fuse, something on that fused circuit is causing the draw.From there you will need to study a wiring diagram to see what is on that circuit.

Of course, all this takes an understanding of electricity to do these test. If you should need assistance with this, I recommend the following inspection; Battery is dead inspection from a certified technician from YourMechanic.

Good luck!

Power steering loss, no belts are turning but the car is running fine. I also have a soft pedal. Whats wrong with my car?
ANSWER : I have only seen this situation once in my 30+ years and it turned out to be a broken crankshaft pulley. Belts are driven by the engine. The crankshaft pulley spins the belts, which in turn spin the air conditioner compressor, power steering and water pumps, and the alternator. The vehicle should be towed to your local repair shop and not driven. Without the water pump spinning to circulate the coolant, the engine will quickly overheat and result in more extensive damage.

Hooked up battery cables to wrong car when jumping it
ANSWER : You may have damaged the car you were jumping from. I have seen alternator, ECM, various relays, and fuses damaged from improper jumping. You should monitor the problem to see if it continues to get worse. If so, have a local expert inspect the clicking noise and pinpoint any appropriate repairs that should be made.

I have changed battery. I think I put non compatible battery initially and it’s start car alarm loud not turned off with remote ac
ANSWER : As long as the nominal voltage of the battery is 12 volts, it’s compatible. Of course, you need sufficient energy storage capacity, too, which in your case is probably around 850 cold cranking amps. As long as you did not reverse the positive and negative terminals (reverse polarity) when you installed the first battery, the battery is not incompatible. When new batteries are installed, inasmuch as any computer settings are lost, there can appear to be electrical problems, but such are not a fault of the battery. If, for example, you are having problems with the engine immobilizer system (security system) you may see a security warning light on the dash. If the warning light is on, to temporarily override the immobilizer system, see these instructions.

If you are experiencing electrical problems with other components, please simply request an electrical system diagnostic and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.