Last Updated: 02.12.2021

So, you’re wondering why your car battery won’t take or hold a charge. 

Is it a bad battery charger? Probably not! Is it battery sulfation? Most likely! 

Battery sulfation is usually the culprit, and when this happens, the battery capacity seems to have reduced so much that it’s acting like a very small battery.

It can be quite frustrating to start your car just to realize that you’ve got a dead or bad battery.

But this is a problem that you can resolve. You just need the tools and the step-by-step process of how to recondition a car battery that won’t hold a charge.

Read on to get the details!

Why Your Car Battery Won’t Hold a Charge?

testing the battery voltage

These are the main reasons why your car battery won’t hold a charge:

Battery Sulfation

So, what is car battery sulfation? It’s when lead sulfate crystallizes into a form that’s no longer electroactive. What this means is that the lead sulfate doesn’t take part in the charge or discharge process.

Sulfation leads to higher internal resistance, decreased current or voltage, and increased charge time. If the level of sulfation is very high, the battery plates cannot supply current. That’s when your car battery becomes useless.

Why and when does it happen? Sulfation normally occurs when your car battery is deprived of a full charge. Every battery discharges over time, and that’s when sulfation can occur.

Bad Cell

Your car battery will eventually develop a bad cell. The other cells in the battery are still working, but one cell can stop functioning, maybe because of a short circuit in the plates. 

When a car battery’s voltage is low, but the state of charge in most of its cells is high, then there could be a bad cell. You can check for a bad cell by measuring the state of charge of the individual cells with the help of a voltmeter or hydrometer. 

You should check your battery cells during spring and fall to avoid being stranded by a failed battery.

Low Water Level

Lack of water is one of the reasons your battery won’t charge. The plates cannot take full part unless they’re completely covered with water. Low water levels will tell you that the acid concentration is too high, which will most likely lead to sulfation. Adding distilled water to your car battery should help resolve or prevent this issue.

Bad Altenator

vehicle's alternator installed on engine room

An alternator is a kind of generator that essentially gives power back to the battery. What happens when an alternator goes bad is that it won’t be charging the battery. Not to mention that it can do funny things with your car’s electrical system.

To get to the root of the problem, check the condition of the alternator drive belt. With the engine turned off, the belt should not be glazed, worn, or cracked. To check for looseness, manually try to spin the alternator cooling fan. 

Apart from causing a bad battery, a failing alternator will also cause the following:

  • The indicator light will display
  • Headlights flickering or dimming
  • The car has difficulty starting or stalls
  • Strange noises produced

Corroded Battery Cables

Your battery terminals and cables can suffer from corrosion. This prevents solid contact, which can limit the charge supplied to the battery from the alternator.

The corrosion on your battery cables and terminals can differ in appearance, texture, and color, depending on the cause of corrosion. The most usual culprit for this is electrolyte leakage.

corroded battery cables or poles

When battery fluid leaks, it accumulates on the cables and terminals. When filling distilled water into the battery, electrolyte leakage leads to corrosion. 

Overfilling the battery with water can very easily cause the terminals to corrode. Corrosion can also happen if the battery is old and it’s been overcharged.

Loose Alternator Belt

A worn or loose alternator belt will contribute to charging woes. This means the charge the alternator produces may not be enough to recharge your car battery.

To check the alternator belt tension, grab the vanes on the front of the alternator and try to turn them, making sure that you’re not using excessive force. If they turn easily, the belt is probably too loose. 

You can also check the tension of this belt, and other belts, by pressing down your thumb at the midpoint between the pulleys they ride on.

Generally, you should not be able to push down more than 1/2-inch if the distance between the pulleys is 18 inches or approximately 1/4-inch if the distance is shorter.

Parasitic Drain

So, your battery and alternator are working just fine, but there’s something else that is drawing the charge. This could be probably because you left your headlights on. The constant power that is drawn from the battery could end up shortening its lifespan.

How to Recondition a Car Battery That Won’t Charge

We’ve just gone through the usual reasons why your battery won’t hold a charge. Now, let’s learn how to recondition a car battery that won’t hold a charge.

What Is Battery Reconditioning?

Battery reconditioning is basically resuscitating or reviving a battery if it’s not charging as expected. This process includes restoring the battery’s standard electrolyte level and full charging capacity.

What You Will Need

  • Safety glasses
  • Plastic funnel
  • Battery hydrometer
  • Battery post cleaner
  • Common screwdriver
  • Voltmeter with probes
  • Battery load tester
  • Necessary chemicals

Step-By-Step Instructions

Here are the steps to follow when reconditioning a battery. Thanks to Watt Barrett for this friendly tutorial.

Step 1: Clean the Terminals

clean the terminals

In most cases, the terminals get corroded. So, it’s best to start the reconditioning process by cleaning the terminals.

Take the battery out of your car and gently place it on the ground. Use tape to cover cell caps to prevent the entry of any cleaning agent. Use a stiff bristle brush and a solution of warm water and baking soda to clean the terminals. Then, use a battery post cleaner to clean the terminals. The stiff bristles provide superior cleaning power for unclogging tough dirt and buildup.

All you have to do is remove the cap on each terminal and then press the brush hood over the post of the terminal for easy cleaning. Turn the battery post cleaner several times. Repeat the same process on the other terminal post.

Step 2: Check Battery Voltage

test the battery voltage

You first need to check your car’s battery voltage. Use either a digital or analog voltmeter. We recommend you allow your car to cool down for at least 12 hours before you do this test. The cooldown duration will allow any surface charge to dissipate.

Attach the positive probe of the voltmeter to the positive lead on the battery, and then attach the negative probe to the negative lead of the battery. You can now check the voltage. 

If your battery doesn’t read at least 12V, you’ve got a problem with one of your cells. 

Next up, check the cells to see if one of them is dead.

Step 3: Test the Cells

test the cells

Check the condition of each cell on your battery. Use a common screwdriver to lift the battery caps and expose the cells.

Check your water level. If your water level is low, don’t worry you will service the water after testing the cells. It is always advisable to have a neutralizing solution (a mixture of water and baking soda) nearby when the cells are opened. 

The battery we’re testing has six cells (12-volt battery), which means each cell should be capable of storing 2 volts of electricity.

Start from the positive terminal. Place one probe on the positive terminal and the other one in the first cell, which should give a reading of 2 volts. Then insert the positive probe into the first cell and the negative probe into the second cell, which should give a reading of 2 volts.

Repeat the same process until the last cell. You must get a reading of at least 2 volts for the individual cells or you’ve got a bad or weak cell.

Step 4: Battery Load Test

battery load test

You need a load tester for this step. The unit has a big carbon filament inside that acts as the resistive load on the battery. It comes with a toggle switch for engaging the carbon filament.

Connect the red hook (positive) to the positive terminal of the battery and the black hook (negative) to the negative terminal of the battery. Set the meter on top of the battery to get the best readings.

You will notice that the reading is in the high green section of the meter at about 13 volts. Do the load test by toggling the switch, which will put a load on the battery. The meter should drop when the switch is on to the yellow zone at about 11 volts. When you let go of the switch, the meter should shoot back to the green zone. This is an indication that the battery is in good shape.

When taking off the load tester always remove the negative terminal first and then followed with the positive one.

Step 5: Hydrometer Test

do hydrometer test

A battery hydrometer is a glass tube that is fitted with a suction bulb that draws the electrolyte from your car battery and up into the glass tube until the float begins to float.

Dip your hydrometer into your battery electrolyte. The electrolyte will be sucked in and the float will move up. Take the reading of the hydrometer—this indicates the specific gravity—as the float stabilizes. The electrolyte becomes denser when the concentration of sulfuric acid is greater.

The battery is healthy when the float is at the green level. If, however, the float rises to the white level, then it is in fair shape. If it rises to the red level, then it needs a charge because the specific gravity of the electrolyte is low.

Read each cell the same way. The cells are likely to give you different readings. You should also check the level of the electrolyte, which should be at least an eighth of an inch above the top of the lead plates.

Step 6: Add the Reconditioning Chemical

add reconditioning chemical

Once you know that your car battery is ready for reconditioning, it’s time to add the reconditioning chemicals. You will need a plastic funnel and a tablespoon. Scoop a spoonful of the chemical and add it to each cell. Then put the battery on the charger and allow it to charge for 24 hours.

What Are the Signs a Car Battery Needs Replacement

You should consider replacing your battery if you observe the following:

Slow Engine Cranking

Slow engine cranking can be caused by a discharged or bad battery combined with cold weather, bad starter motor, and poor or loose battery cable connections. Engine cranking speed should typically be approximately 200 rpm.

Check Engine Light

A bad, failing, or discharged battery can cause some serious problems in your car’s electronic and electrical components, including the computer. It may cause the Check Engine Light to display.

Low Battery Fluid Level

The battery fluid is made up of sulfuric acid and water. A bad or failing battery will have low battery fluid levels. Low fluid levels could lead to slow engine cranking, flickering battery or alternator light, and dimming lights.

Battery Leak

Also referred to as battery acid leakage, a battery leak when sulfuric acid finds its way out of the battery. You can know a battery is leaking if it has visible cracks in its casing. You should also look for bubbling fluid escaping through the cell caps. Your car battery may also appear distorted, inflated, or warped.

The Age of the Battery

The average lifespan of a car battery is approximately three to five years. As it ages, so does its ability to hold a charge. At some point, you will have to replace the battery with a new one.


Can a Car Battery Hold Charge and Still Be Bad?

If your car battery is not holding a charge higher than 10.5V, then this is telling you that it’s a dead cell. The battery is usually sulfated when it is fully charged but has a voltage of less than 12.5V. Consider the battery to be bad if it can’t reach a full charge.

What Type of Car Battery Never Needs Charging?

All the car battery types we have come across need charging.

Are There Any Safety Precautions to Consider?

Always go through your battery and vehicle manuals for safety instructions before reconditioning a battery. Wear protective clothing and safety glasses. Work in a well-ventilated environment and keep the whole process away from any ignition source.

Final Thoughts

The battery under the hood of your car should live for about three to five years with good maintenance. There are no guarantees beyond the battery’s warranty though.

But a serious car owner willing to check, service, and clean the battery and its connections and terminals should be able to have that battery start and run the car for more than half a decade. Our detailed guide on how to recondition a car battery that won’t hold a charge should make maintenance easy for you.

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