# Question: How Do I Know If My 12 Volt Battery Is Bad?

## What should a 12 volt battery read when fully charged?

That’s only a difference of 0.25 volts on each cell from fully charged to fully discharged.

So a 12volt battery will measure at about 12.9 volts when it’s fully charged and about 11.4 volts when it is fully discharged.

That’s a total of 1.5 volts that represents the full range of charge on a 12volt battery..

## Can a battery have 12 volts and still be bad?

A voltmeter is the most reliable way to determine if a battery is holding its charge. … If the voltmeter shows no reading or a reading below 12.4 volts, the battery is dying. If the voltmeter reads 12.4 volts or higher, the battery is fine and the problem lies elsewhere. Start your car.

## How long does it take to charge a 12 volt battery?

12-24 hoursA 12-volt battery could take up to 12-24 hours to charge fully. When recharging your battery, remember that if it gets too hot while you’re charging it, you need to stop charging. It should not get too hot above 125 Fahrenheit. Ideally, slow charging your batteries is the best option.

## How do you test a 12 volt car battery?

To test the voltage, make sure to connect the battery cables. Start the ignition while holding the leads on the positive and negative terminals. You will notice that the voltage will drop, but it should not drop below 9.5 volts. It needs to be replaced if it drops below this voltage.

## Can a battery test good but still be bad?

As long as battery voltage remains above 9.6 volts, the battery is considered “good.” But if it drops below 9.6 volts by the end of the test, the battery may be “bad,” or the battery may have to be recharged and retested if it was not fully charged prior to the test.

## Can you bring old batteries back to life?

Rechargeable batteries are a great way to save money — and the environment — but some devices can discharge batteries to the point where they cannot be recharged. This charger can revive them, saving you even more money!

## How do you rejuvenate a battery?

Add distilled water to Epsom salt to forma thick liquid and stir it properly to dissolve Epsom Salt well. Pour the mixture of distilled water and Epsom salt into every battery cell battery as much as possible. Plug in your charger after having the battery covered and set the charger for High Amps (high current).

## At what voltage is a 12 volt battery dead?

This is called the “open-cell” or “resting” voltage of the battery. Resting fully charged 12-volt batteries are around 12.8-12.9 volts, and flat dead ones are at 12.0 volts, so 12.4 volts on a resting battery means it’s about 50% charged.

## How do you restore a 12 volt battery?

Mix ¼ Epsom salt with ¾ warm distilled water. You need a quart of this mixture for one cell. Pour the mixture into the cells and shake it around before letting it sit. Connect the charger for the battery and charge for 12 hours.

## How long should a 12 volt battery hold its charge?

The actual resting voltage, or the voltage a battery will settle at 12-24 hours after being removed from the charger, is closer to 2.1 volts per cell, or about 6.4 volts for a 6v battery, and 12.7 volts for a 12v battery. These numbers assume 100% healthy cells, and may vary a bit lower for older batteries.

## Can a bad cell in a battery be fixed?

If a cell is still faulty, it probably has been damaged by sulfation. The cause, low specific gravity of the electrolyte, converts lead and sulfuric acid into hard, lead-sulfate crystals. Take the battery to a technician who can advise whether to repair the battery or buy a replacement.

## How do you check if a battery is good or not?

All you need to perform the test and check if your alkaline batteries are juiced is a hard surface. Drop each battery (with the flat, negative end down) from a couple of inches up. If the battery is charged, it should make a solid thud and most likely stay standing.