How can you tell if your car battery is dead?

Answer 1

This is easy - you can determine the functionality of the alternator in less than 5-minutes. With the engine off, using a volt meter switched to measure DC current, place the red lead against the positive battery terminal/post and the black lead against the negative battery terminal/post and test the voltage. A good battery should measure around 12-volts (a good battery has a range of slightly lower to slightly higher than 12-volts). If you get within this range you have a properly charged battery and can then move to the next step and test the alternator.

Turn the engine on and again place the red lead against the positive battery terminal/post and the black lead against the negative battery terminal/post and test the voltage. The alternator is designed to generate enough voltage to replace the 12-volts of power being used by the vehicle's electrical system and charge the battery at the same time. Therefore, a properly working alternator will push about 14-volts of electricity into the system (a properly functioning alternator will generate a range of slightly lower to slightly higher than 14-volts).

If the system is generating around 14-volts with the engine running, then you can reasonably conclude that the alternator is working properly.

If you you are having battery charging problems (will not hold a charge) and the system is pushing around 14-volts with the engine running, you can then reasonably conclude that the battery needs replacing. If the system is producing less than the normal range of about 14-volts, you may need to replace the alternator. Keep in mind that a good battery may go bad if it is repeatedly used in a system in which the alternator is not working properly. If the systems tests within the normal range of 14-volts while the engine is running, replace only the alternator first and see if the battery then holds a charge. If it doesn't, then you will need to replace the battery also.

Answer 2

Lots of things can go wrong. The bearing that is belt driven can fail. It can over, or undercharge your system. The best check is to check it's running voltage - it should be between 13-14.5 volts. Anything less than 12.5 and it's not charging your battery.

Answer 3

If your battery is always going dead a day or two after a boost, then it most likely the alternator. Two surefire ways to see if the alternator is bad is to take the positive (red) battery cable off after starting the car. If the car still runs, alternator is good. If the car stops running, then it is likely the alternator. The battery is just to turn the car on and then the alternator regulates the initial charge coming from the battery and that powers the car.

Another thing you can do is to run a voltage check at either the battery or on the alternator with a Volt Ohm Meter (VOM). If the voltage comes back as 13.5V or better, than the alternator is good. Less than 13.5V, and it is likely the alternator.

Be advised, though that what could look like an alternator problem could also be your ignition switch or starter.

Answer 4

unplug the negative battery terminal while the vehicle is still running.......if it dies, then more than likely the alternator is bad. if it still runs then the alternator is prolly still good

That procedure can damage today's alternators. Better off using a voltmeter and test battery voltage at the battery before you start vehicle then again after it is running. A fully charged battery should read 12.68 Volts and if the charging system is healthy, 14.5 Volts while it is running. If the battery is not fully charged you will not get an accurate reading of the charging system.

Answer 5

Answer

Hey there friend To check if alternator is false or not there is a simple way of doing it without getting to tear entire car and cables apart. Before you do anything loosen the negative cable but so its still connected to batter.

Start the vehicle, if cant slave it off and start it, while vehicle is runing disconnect the negative wire that you have loosened then if vehicle is runing its good if it dies then your alternator went bad and needs replacment.

If you need to drive badly because cant get a ride to get to schucks or some auto parts store you can bang the heck out of the alternator with a hammer which will charge the coil inside and will loosen some of the dust that collected there. That should be enough for you to get to store and back.

Good luck you can always Private msg me if you have any other Auto Questions.

Good Day.

Removing a battery cable while the engine is running is not a good idea. You can damage a good alternator and or sensitive electronic devices by doing so. It is best to attach a voltmeter to the battery and take a reading before you start engine and after engine starts and is running at an idle. Before it starts the battery needs to be fully charged and give you a voltage reading of 12.68 volts or you won't get a correct reading of the alternator. Start and run engine at idle with no accessories on, the reading should be 14.2 + or - .5 volts if you have a healthy charging system.

Answer 6

There's a lot of ways you can tell but if you do a battery test ,to test the liquid on each cell it will be a faster way than rather guess if its good because by that you can measure each Individual cells charge levels

Answer 7

Get a digital multimeter. Set it to measure voltage. With the engine running, place the black diode on a good ground point (battery negative will work), and place the red diode on the post on the back side of the alternator where the wire which runs to the battery positive terminal is connected to. You should be getting a reading in the vicinity of 14 volts. If not, your alternator needs to be replaced.

Answer 8

When the battery will no longer accept a charge and cannot provide the required power to operate your vehicle. Have your local auto parts store test it for you.