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What Is a Sulfated Battery?

Power - by Joe Weber - updated on 9/27/2023

Yellow top battery with sulfation

If corrosion is the most common cause of early battery failure, sulfation is a close second. Most of us don't even know what sulfation is. This blog will answer that question and why it is such a bad thing for batteries for our lead batteries. Keep reading to learn what sulfation is and how you can prevent and potentially reverse battery sulfation with proper charging and the use of a battery maintainer.

What Is Battery Sulfation?

Unlike corrosion, you can't see sulfation unless you open up the battery to see the internals (Please don't try to do that). Battery sulfation is the buildup of lead sulfate crystals on the plates in the battery and is one of the most common causes of early battery failure.

All lead-acid batteries will accumulate sulfation during their lifetime as a normal part of the chemical processes of the battery. But, sulfation builds up most and will start to cause problems when your battery is undercharged, stored in excessive heat, or stored without a full charge.

Example of sulfated battery

Is Battery Sulfation Bad?

I like to think of sulfation as arthritis. A little bit may cause some discomfort, but a lot can really impact your daily life. Having a little sulfation buildup may not cause drastic issues but a lot can be a huge problem and can lead to several issues that you don't want to deal with:

  • Longer charging times
  • Shorter running times
  • Excessive heat buildup inside the battery
  • Diminished starting/cranking power
  • Considerably shorter battery life
  • Complete battery failure

Don't worry, it's not all bad news! You don't need to immediately go out and buy a new battery if you notice some of these symptoms. In many cases, as you'll see below, sulfation can be reversed to return your battery to near-perfect condition.

How Do You Reverse Battery Sulfation?

The first thing to do is to determine what type of sulfation your battery has. Battery sulfation is seen in two forms; luckily, their names are self-explanatory, permanent and reversible. Like many things in life, early detection is key for battery sulfation to be reversed and bring the battery back to optimal condition.

Permanent (Hard) Sulfation

Permanent sulfation can occur when you store a battery in a low state of charge for a longer period like several weeks or months with no maintenance. If you store your battery without a full charge and leave it alone, you are more likely to end up with a battery with permanent sulfation. Permanent sulfation can sometimes be salvaged but it is pretty uncommon, and is more likely that you will need to replace the battery.

Reversible (Soft) Sulfation

When you properly charge your battery and you pay attention to the signs, you can catch sulfation early enough so the lead sulfate crystals will not have had enough time to build up on the plates to the point of no return. This will make it easier to correct and is, most of the time, fixable.

How Do You Fix A Sulfated Battery?

As its name suggests, reversible sulfation is, well, reversible. In order to accomplish this you need to apply an overcharge to a fully charged battery using a regulated current of around 200mA (milliAmps) for roughly 24 hours. This allows the battery terminal voltage to rise between 2.50 and 2.66 volts per cell. This also increases the battery's temperature to a range of 122–140°F. These two factors combined will help dissolve the lead sulfate crystals that have built up on the plates.

Does this sound like something you want to do? Or would you rather just charge and store the battery properly to avoid having to take the time to do this? I think those are pretty easy questions to answer.

Prevention is the best thing you can do for your battery. The best way to accomplish this is to store your batteries correctly when not in use. Store the battery at a full charge to help prevent the volts from dropping to below 12.4 volts.

You can also stop the voltage from dropping by using a battery maintainer. When you're storing your battery with a battery maintainer, just connect it, forget it and let the maintainer do the work without the worry of damaging your battery.

What Does a Battery Maintainer Do?

A battery maintainer will send small amounts of energy to your battery, keeping the battery at an optimal charge level for storage when the battery isn't being used for a long period.

What Should I Do if I Need a New Battery?

Is your battery showing the signs that something may be wrong but you aren't sure? No problem! The battery experts at Batteries Plus will be happy to test it for you, free of charge. If your battery is beyond repair and it's time to look for a replacement battery, we have a large selection of batteries to fit your needs. Let our team of trusted experts at your local store help you find the best battery for your car or truck, boat, RV and more!

If you would like to learn more about corrosion and sulfation read our blog post "What Causes Battery Sulfation and Corrosion?".

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