How To Revive An Old Car Battery (9-Step Guide)

The question is: can you revive an old car battery? Or do you need a new one?

In this guide you'll learn:

  • How a Car Battery Works
  • Why Car Batteries Go Bad
  • Supplies You'll Need to Revive an Old Car Battery

And much more! 

How to Fix That Old Car Batter? Here's how to Bring it Back to Life

Few sounds are as discouraging as that of clicking or slow cranking when attempting to start your car.

The moment that these sounds are heard usually comes accompanied by the hanging of your head or a few choice words spoken.

So, if you want to learn how to extend your old car's battery life, keep reading to see our step-by-step guide:

How A Battery Works

No one looks forward to being forced to deal with a dead car battery. Battery failure always seem to occur at the most inconvenient times, and the cost of purchasing a new battery can be quite high.

When a failure of this nature takes place, only two options exist:

  • Buy a new battery or...
  • Attempt to revive the one that has failed

Many individuals today are surprised to hear that reviving their dead battery comes as a viable option in many cases.

However, armed with a few specific tools and a little know-how, breathing new life into a dilapidated battery is often far easier than one might think.

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The Nuts & Bolts of Car Batteries

To understand how to revive a failed battery, you must first understand how a battery works. 

While not overly complicated to grasp, the details relating to a battery’s operation carries more depth than just providing power to your vehicle’s electrical systems.

Lead-acid batteries are the most common type of battery found in today’s automobiles. Inside these batteries are a series of cells that contain positive and negative plates, that are submerged in sulfuric acid.

There are six such cells in a 12-volt battery. Each cell carries a charge of 2.1 volts, equalling 12.6 volts in total.

Each plate contained within a battery’s cell is coated in an active material, with sponge lead being used for negative plates and lead dioxide for positive plates.

A chemical reaction takes place upon a load being put on the battery cells, as these active ingredients contact the sulfuric acid contained within.

The product of this chemical reaction is thereby converted to chemical energy for use by your vehicle’s starter.

Why Batteries Go Bad

A number of issues can take place within your car’s battery that reduces its battery life.

Issues such as electrolyte loss or poor charging can lead to battery sulfation. When sulfation occurs, a battery loses some of its natural ability to convert chemical energy to electrical energy.

This stems from a battery’s inability to perform the necessary chemical reaction between its acids and active materials to the degree that it once could.

When this occurs, issues with poor engine cranking often become evident and your battery will stop recharging itself properly.

This is the point at which many consumers discard their old battery in favor of a new replacement.

However, this can lead to excess expenditure that can often be avoided if you learn how to recondition batteries to give your car's battery the longest battery life possible.

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Did You Know: Car battery facts

How to Recondition Batteries A DIY Project?

Most shops will not attempt to revitalize a battery, as a simple replacement is less time consuming, and these shops can sell a new battery to the consumer in the process.

Because of this, if you intend to have your battery reconditioned, your only option typically becomes doing so yourself.

Handling batteries, especially when working around acid, can be quite dangerous. Care must be taken to always wear personal protective equipment. 

At the bare minimum, rubber gloves of elbow-length and goggles should be worn when attempting a repair of this nature.

If you feel as if you are uncomfortable with the idea of working around battery acid and other corrosive chemicals, or you do not have the suitable personal protective equipment at your disposal, complete battery replacement will likely be your best option.

If you do decide to tackle DIY battery reconditioning, you will likely be saving yourself a considerable amount of money.

The supplies needed to complete this task are no more than basic hand tools, distilled water, and a manual battery charger.

Assuming that you have basic hand tools and a battery charge available to you, the entire revitalization process will likely cost less than $10.

This is a vast improvement over the costs of new battery replacement, especially if done by an industry professional. Typical costs for new battery installation are as follows:

Low End Cost

$75 (Battery) + $20 (Installation) = $95

Average Cost

$110 (Battery) + $20 (Installation) = $130

High End Cost:

$150 (Battery) + $20 (Installation) = $170

As you can see by the numbers above, revitalizing and reconditioning your battery can save you a sizable amount of money in the long run. Any expenditure in time that is required to revitalize your battery is easily justifiable.

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Supplies You'll Need to Revive An Old Car Battery

The supplies that are needed to complete a task of this nature are minimal. The following are some items that you will need on hand when revitalizing your battery.

  • Personal Protection Equipment - At a minimum, elbow-length rubber gloves, as well as goggles should be worn for the duration of this project.
  • Wrenches/Small Flathead Screwdriver - You will need a basic set of metric wrenches for removing battery cables, as well as battery hold-downs. A flat head screwdriver will be used to remove caps from the battery's casing.
  • Manual Battery Charger - A battery charger will be needed for cooking off excess sulfation. This requires the use of a manual boost mode. New digital chargers self regulate and typically do not allow the use of this mode at-will.
  • Epsom Salts - Epsom salts will be used to produce a mixture for topping off the contents of each cell.
  • Distilled Water - Distilled water will also be used as the other part of the mixture that is utilized when topping off cells.
  • Miniature Funnel Or Dropper - A miniature funnel or dropper will be needed to pour liquid contents into each cell.
  • Multimeter - A multimeter will be used to verify the successful revitalization and recharge of your battery. 

How To Revitalize An Old Car Battery in 9 Steps

  1. Remove Battery From Vehicle
  2. Remove Battery Caps
  3. Mix Water Solution
  4. Add Mixture To Cells
  5. Cook Sulfation From Lead Plates
  6. Recheck Fluid Levels/Replace Caps
  7. Place On Trickle Charge
  8. Test Battery
  9. Reinstall and Test

The following steps should be followed in the exact order in which they are listed when attempting to successfully revitalize a drained battery. A failure to do so can result in damage to equipment, as well as personal injury.

Step 1 - Remove Battery From Vehicle

With the use of a basic set of metric wrenches, remove the battery in question from your vehicle. This will require the battery’s positive and negative cable to be removed, and all battery hold-downs to be disengaged.

Step 2 - Remove Battery Caps

You will now remove the caps at the top of your battery’s casing.

This will allow you to gain access to the battery cells and battery plates. On some batteries, this requires the removal of two side-by-side rectangular caps.

On other batteries that are deemed to be maintenance-free. Six individual caps can be located under the battery's data sticker.

Simply peel up the sticker to reveal the caps. No matter the style of cap, removal can be completed by gently prying with the use of a small flat head screwdriver.

Step 3 - Mix Water Solution

In the majority of situations, you will find that the fluid level in each cylinder is slightly low. This will be remedied by adding a solution consisting of Epsom salts and distilled water.

Simply pour ½ liter of distilled water into a suitable container. Next, add as much Epsom salts as can be completely dissolved within. Heat this mixture to an approximate temperature of 150 degrees Fahrenheit. 

Step 4 - Add Mixture To Cells

With the use of a small funnel or appropriately sized dropper, top off each individual cell with epsom salt solution. Fill these cells to a level that is just below the point that each sealing cap will bottom at. 

Step 5 - Cook Sulfation From Lead Plates

You will now cook the accumulated sulfation from the lead plates contained within the battery.

Do not replace cell caps prior to this step. Start by placing both the hot and ground leads from the battery charger to their respective posts on the battery. Always remember, positive to positive, negative to negative.

Next, plug up your charger and set it to the boost/start range. Allow it to charge for 15 minutes. Now turn off the charger and allow the battery to sit for one hour. After being allowed to sit, you will complete this charge cycle four more times utilizing the same time-frame intervals.

Step 6 - Recheck Fluid Levels/Replace Caps

Shine a light through each cell cap hole to observe the electrolyte level. If any of these levels appear low, top them off with the same solution used in step 3 and 4. You will now replace all cell caps at the top of the battery.

Step 7 - Place On Trickle Charge

Your battery will now be placed on a trickle charge to slowly bring it back within voltage specifications. Simply hook up your battery charge as previously described, and adjust the settings to its slowest charge rating.

Step 8 - Test Battery

After being allowed to receive a full charge, you will now need to test your reconditioned battery. This can be accomplished with the use of a multimeter set to the DC volts setting. Verify that battery output is at 12.6 volts (+/- .2).

Step 9 - Reinstall and Test

You will now reinstall the battery into your vehicle in the opposite fashion in which it was removed. Ensure that all battery terminals and hold-downs are tight. Once this is complete, cycle the ignition to test for functionality.

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Bringing A Battery Back From The Dead

Although attempting to revive an old automotive battery can seem labor-intensive and time-consuming, the reality is that this process is only a small inconvenience in relation to the money that will be saved over a complete battery replacement. With an afternoon’s worth of work and a little ingenuity, you will have your old battery restored to its former glory, and your vehicle starting with the reliability that we all seek to achieve.

About Your Mechanic

About Josh Boyd

I’ve been an ASE Certified automotive/heavy equipment technician since 2010. I began my career performing basic automotive maintenance at a service center before working as a Toyota technician at my local dealership.

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