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What Is a Sulfated Battery?

Batteries Plus Blog - Power - by Joe Weber - updated on 9/14/2022

Battery with sulfation

One of the most common causes of early battery failure is battery sulfation. What is sulfation and why is it such a bad thing for batteries? Read below to learn what sulfation is and how you can potentially reverse battery sulfation with proper charging and the use of a battery maintainer.

What Is Battery Sulfation?

While you can't see sulfation unless you open up the battery, battery sulfation is the buildup of lead sulfate crystals on the plates in the battery and is the most common cause of early battery failure. All lead-acid batteries accumulate sulfation in their lifetime as part of the normal chemical processes of the battery. But, sulfation builds up most and will start to cause problems when your battery is overcharged, stored in excessive heat, or stored without a full charge.

Another common issue seen is a flakey brown, white or green substance on the terminals called corrosion. Learn how to remove and prevent corrosion on your batteries by reading our blog article "What is Car Battery Corrosion and How Do You Prevent It?".

Example of sulfated battery

Is a Sulfated Battery Bad?

The simple answer is a simple, yes. The buildup of lead sulfate crystals can lead to several adverse outcomes such as:

  • Long charging times
  • Short running times
  • Excessive heat buildup
  • Considerably shorter battery life
  • Total battery failure

It's not all bad news though and you should not immediately go out and buy a new battery if you notice some of these things. As you'll learn below, this phenomenon can be reversed in many cases to return your battery to near-perfect condition.

Can You Reverse Battery Sulfation?

In many cases, sulfation can be reversed. The first thing to do is to determine what type of sulfation your battery is experiencing. Battery sulfation is seen in two forms and luckily for us their names are self-explanatory, permanent and reversible. Like many things, early detection of battery sulfation is key to being able to reverse the sulfation and bring the battery back.

Permanent (Hard) Sulfation

Permanent sulfation occurs when you store a battery in a low state of charge for several weeks or months. While batteries with permanent sulfation can sometimes be salvaged, it is more likely that you will need a new battery.

Reversible (Soft) Sulfation

If caught early enough the lead sulfate crystals will not have had enough time to build up to the point of no return on the plates. This will make it easier to correct and is fixable.

How Do You Fix A Sulfated Battery?

Reversible sulfation can be reversed as its name suggests. To accomplish this you must apply an overcharge to a fully charged battery using a regulated current of around 200mA (milliAmps) for roughly 24 hours. This will allow the battery terminal voltage to rise between 2.50 and 2.66 volts per cell. This will then also increase the battery's temperature to a range of 122–140°F. These two factors combined will help dissolve the lead sulfate crystals.

The best course of action is to prevent sulfation altogether. The way to do this is to properly store your batteries when not in use. Store the battery at or near a full charge to prevent the volts from dropping to below 12.4 volts. Another way to prevent the volts from dropping is 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 Should I Do if I Need a New Battery?

Not sure how bad your battery is? Stop by to have it tested free of charge. If your battery is beyond repair and it's time to look for a replacement battery, look no further than the experts at Batteries Plus. 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!

For more information on sulfation and corrosion read our blog article "What Causes Battery Sulfation and Corrosion?".

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