How to Fix a Dead Cell In A Car Battery

A fully functioning car battery should produce 12.7 – 13.2 volts when fully charged. However, the battery may sometimes be unable to provide more than 10.5 volts. This is usually a sign that there’s a problem, one that needs you to know how to fix a dead cell in a car battery.

Unfortunately, you can’t use half of the electricity you need and wait to use the other half later. A drop in voltage means that you will not have sufficient juice to start or run the car. Neither will you be able to use most of your car’s electricals.  

Can you fix a car battery with a dead cell?

Yes, you can. The best way to fix a car battery that has a dead cell is to refurbish or recondition it. This is if you do not have the money to buy a new one. A dead cell is a telltale sign that your battery is about to completely fail.

And, having a dead battery is definitely something you do not want to happen. It can leave you stranded in the middle of the road when heading to work or in a deserted area. Thankfully, there’s a way you can revive it and this article will explain how to fix a dead cell in a car battery well.


How to refurbish and recondition a dead cell in a car battery

What you’ll need:

  1. 1 lb. Epsom salt (450g Magnesium Sulfate)
  2. 1 lb. baking soda
  3. Eye protective goggles
  4. Chemical-resistant gloves
  5. Apron
  6. Flathead screwdriver
  7. Empty plastic buckets
  8. Battery charger (Slow trickle type)
  9. Digital multimeter
  10. Distilled water
  11. Plastic funnel
  12. Toothbrush/Wire brush


Step 1: Wear protective gear

Wear your goggles, protective apron, and gloves. You’ll be dealing with battery acid which is dangerous. The gear protects the exposed parts of your body from burns and spills.

Step 2: Find a well-ventilated area

Find a spot away from any sources of fire. Battery acid is flammable. Also, exposure to sulfuric acid fumes can cause tightness in your chest, respiratory irritation, and difficulty breathing. You want to work in a well-ventilated area. Avoid working directly under direct sunlight.

Step 3: Clean your battery

Carry out a visual inspection of the battery. Ensure that the terminals are not covered by green matter, grime, or rust. If you see any corrosion, mix baking soda and clean water and use this to scrub the corrosion off the terminals with a toothbrush or wire brush.

Step 4: Open the battery cells

How to Fix a Dead Cell In A Car Battery

Using a flathead screwdriver, pop off the caps that cover the cells. Some batteries include a top cover above the cell caps that you’ll need to pry off first. It provides extra protection against water and other external elements.

Step 5: Pour out the battery acid

How to Fix a Dead Cell In A Car Battery

Lift the battery and tilt it to pour the acid into an empty plastic bucket. Be careful not to spill any acid on the floors or on yourself. Keep the bucket away at a safe spot and make sure your battery is facing upwards once done.

Step 6: Clean the battery cells

Mix half a pound (225g) of baking soda and half a gallon (2 liters) of water. Pour the mixture into the battery cells using a plastic funnel and close the cells.

Lift the battery and shake it for two minutes. Since batteries are heavy, you can shake yours repeatedly while taking breaks. Empty the solution into a bucket once you’re satisfied that it has sloshed well inside the cells.

Step 7: Make the electrolyte

Heat about half a gallon (1 liter) of distilled water to a boil. Pour half a pound (225g) of Epsom salt and stir. Keep stirring until the salt dissolves completely. This will be your electrolyte.

Do not use vinegar as an electrolyte. It contains about 5% acid in water which makes it harmful to batteries. Vinegar also reduces the performance, life expectancy, and endurance of your battery. It eats away at the lead pates over time.

Step 8: Pour in the electrolyte

Start by cleaning and rinsing your plastic funnel to remove traces of the baking soda solution you used in step 6. Pour the electrolyte into the battery cells until the lead plates are immersed. Bottle any remaining solution for future use.

Step 9: Charge the battery

How to Fix a Dead Cell In A Car Battery

Connect the positive battery terminal to a battery charger and then the negative terminal. Leave the cells open without the cell caps. Charging releases gases that can build up and cause an explosion.

Also, the charger you use should be a slow trickle charger and not a fast charger. It will prevent the battery from running low. Leave the battery to charge for 36 hours.

Step 10: Test the battery

How to Fix a Dead Cell In A Car Battery

Set your digital multimeter to volts and connect it to the battery terminals. The multimeter should read 12.43 volts or more. If it reads less than that, charge the battery for another 12 hours.

Reinstall the battery in the car and test it. You can start by switching on your headlights for a few minutes.

Read more: How to Reset Key Fob After Changing Battery

What happens if a battery has a dead cell?

A battery that has a dead cell will not provide the voltage required to operate the car. You may notice that your car has a starting problem. This is normally an indication that something is wrong with the battery. A dead cell is a sign that the battery is going bad and that it must be replaced or refurbished to bring it back to life.

What are the signs of a bad cell in a car battery?

Some of the symptoms of a dead cell in a car battery include:

  1. Slow cranking. The dead cell prevents the battery from holding the amount of voltage needed to crank the engine.
  2. Battery that reads below 12 volts.
  3. Clicking sounds on start-up indicating a starting problem.
  4. Vehicle electronics that don’t work. For example, dimming headlights.

Read more: How to Change the Battery in a Car Key Fob

How do you check a car battery for a dead cell?

Test the battery voltage using a digital multimeter. If you get a zero reading, the battery most likely has a short circuit. If you charge your battery but can’t get it to provide more than 10.5 volts, it most likely has a dead cell. Sulfation is also another common problem that causes the battery voltage to drop.

What causes a dead cell in a car battery?

Below are some of the things that can lead to a dead battery cell.

  1. Corroded or loose battery connections
  2. Electrical drains that occur often
  3. Problems charging the battery
  4. Extreme weather that affects the functioning of the battery
  5. More power demand than the alternator can provide

How long can a car battery last with a dead cell?

A battery that has a dead cell will not last very long. It’s usually a sign that the entire battery is just about to fail. Shortly after the cell dies, the car may refuse to start on the next start-up or stop in the middle of nowhere due to a dead battery. You can extend the life of a dead battery for another 3-5 years by reconditioning it.

Can you drive with a dead cell battery?

No. You will most likely not be able to start a car that has a dead battery cell. This is because the amperage will not be enough to start and operate the vehicle.

If you’re lucky enough to get the engine cranking, the car may not be very far away from completely stalling due to a dead battery.

Can a dead cell drain a battery?

A dead cell can drain a battery in a car that has stayed off for a while. It will prevent the car from starting as it normally does. You’ll hear several clicks as the engine struggles to crank.

This is a sign that there’s no power. Even if you have power, it will be too little to operate the car and any of the electricals. You’ll have to replace the battery with a new one.

Read more: How to Tighten Loose Battery Terminal

Will a car battery charge with a dead cell?

Yes. A car battery with a dead cell will charge. But, it will not provide enough voltage for the car to operate at its optimum. Most of the time, the voltage will not get any higher than 10.5 volts. A fully charged battery provides 12.7 – 13.2 volts which is enough to get you to wherever you want to go and back.

Can you jump a battery with a dead cell?

Yes. Jumping the battery will bring it back to life temporarily. However, the battery will not be able to hold the charge needed to start the car on the next start-up.

Jumping it every time will only get you to where you want to go with no guarantee that you will come back. Furthermore, the battery could fail completely and leave you stranded.

Can a bad cell in a battery cause the alternator to fail?

Yes. A battery with a bad cell can cause the alternator to work harder than normal to provide enough voltage to start and operate the car. It measures the amount of charge the battery needs by checking the reference voltage.

Depending on how bad the battery is, it may be forced to turn on and off more often than it’s required to. This causes it to overheat and eventually go bad.