What does sul mean on a battery charger? Sulfated battery

What does sul mean on a battery charger? Sul means the formation of lead sulfate crystals on the battery plates. It blocks the flow of electricity between the plates and prevents the battery from recharging.

Sulfation is a primary cause of battery failure in all automobile applications. It’s a rapid process that may take only 24 hours to set in. However, several factors can trigger the sulfation process. Let’s find out what causes batteries to sulfate and how to prevent it.

What Does Sul Mean on a Battery Charger?

If you never hear the word sulfation on a battery, you probably wonder: what does sul on battery charger mean?

It refers to the sulfate buildup on a battery surface. This buildup prevents current from flowing efficiently and can make a battery unserviceable.

What does sul mean on a battery charger

Sul is also an indication of a battery charger error code. The sul code on battery charger indicates the charger finds a sulfated battery.

However, it’s normal for small sulfate crystals to develop during usage. But many crystals form on the plates when a battery suffers from extended charge deprivation, which reduces lead oxide (the battery’s active component). As a result, it prevents the conversion of chemicals into electricity.

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Causes and Symptoms of a Sulfated Battery

Undercharging and overcharging the battery can lead to its sulfation. It can also happen when you keep the battery in a high-temperature environment. Unused battery units are also at risk.

So, how do you know if your battery has already been affected? Well, some clear signs will hint at the upcoming hazard.

Constant heat buildup is one of the leading symptoms. But that’s not the only one. Below are some of the other symptoms:

  • Sulfated batteries don’t function properly
  • Discharged batteries not holding a charge
  • Longer charging times
  • Batteries discharge too quickly when not in use
  • Batteries get hot even when not in use
  • Battery failure

How to Diagnose a Sulfated Battery?

What does sul mean on a battery charger? The diagnosis gives you a clear view of the process. Here are the steps to diagnose a sulfated cell by digital voltmeter:

  • Recharge the battery to its full charge.
  • Rest the battery overnight before checking the circuit voltage to prevent misreading.
  • Measure the battery’s voltage. If you find the voltage <12.4 V, it’s an indication that the battery is sulfated. A reading higher than 12.4 V means you can still recover the battery.
  • Charge the battery again and rest it for 72 hours.
  • Repeat until the battery voltage reaches maximum capacity, or no improvement is evident.

What Are The Effects Of A Sulfated Battery?

Prolonged charging periods and excessive heat build-up might occur when sulfates accumulate. Furthermore, decreased charging times, battery efficiency, and battery breakdown might be detected.

Sulfation causes a considerable loss in cranking performance and affects the battery cycle-life. When trying to ignite your automobile, you could find that the battery fails. Sulfation also raises the likelihood of boil over, which occurs when acid boils and spills over the battery.

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Sulfation also reduces your battery’s functional running times among charges. Any above factors might cause a battery system to die sooner than intended.

How to Fix a Sulfated Battery Unit

Sulfation is a common issue for lead acid batteries. There are two types of sulfation in battery chargers: reversible and irreversible or permanent.

What does sul mean on a battery charger

Here is how to fix a sulfated battery:


To fix this problem, you must overcharge a fully-charged battery with a 200mA. Raise the terminal voltage to 2.50 – 2.66 V for 24 hours. It will increase the battery temp to 122–140°F (50–60°C) and dissolve the sulfate crystal.

You can also use an anti-sulfation system for the battery terminals that prevent reverse sulfation.

Irreversible or permanent

When the battery remains uncharged for a prolonged time (weeks to months), the battery plates may become covered with lead sulfate crystals. In that case, you cannot restore the unit.

Using a battery desulfator

The sulfation develops due to undercharged batteries. Reversing the procedure becomes difficult for a converter to complete on its own.

Yet, a cell desulfator can be used to restore adequate levels. A desulfator can remove any sulfate crystals by subjecting the batteries to high-voltage surges.

How to Prevent Battery Sulfation?

The easiest way to prevent sulfation is to charge your battery correctly. Do it by using a compatible charger and keeping your battery charged.

Below are a few quick tips that may help you avoid sulfation:

  • Charge batteries after each full discharge and before long periods of non-use.
  • Avoid overcharging or over-discharging your batteries.
  • Use the battery regularly.
  • Clean the battery terminals periodically.
  • Be sure to store your batteries in a cool, dry place.
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Can You Charge A Sulfated Battery?

Yes, but you might need to raise the power to break down the hard lead sulfate crystals. If the battery temperature rises over or above 125° F, you should consider stopping the charging process and cooling down the battery before resuming.

Finally, you may cycle the battery, deplete it to 50%, and then recharge it for several cycles to evaluate its endurance.


What are the recommended chargers to recover sulfated batteries?

Using a battery desulfator charger is the best way to restore sulfated batteries. The charger will clean out and remove any sulfation in the battery.

Does a battery Desulfator really work?

Yes, a battery desulfator can recover sulfated batteries. It’s an inexpensive device, so try it before using other methods.

Is a sulfated battery ruined?

Permanent battery sulfation can cause a variety of issues including: Loss of starting/cranking power. Substantially longer charging times. Increased heat build-up.

How long does it take a battery charger to Desulfate a battery?

Depending on the size of the battery, the desulfation process can take from 48 hours to weeks to complete.

What causes a battery to sulfate?

Batteries develop sulfation each time they are used (discharged – recharged). If they are overcharged or undercharged or left discharged, some for even just several days, they will rapidly develop sulfate. Even when a battery is stored fully charged, sulfate will form unless a desulfating battery charger is used.

Above is information about What does sul mean on a battery charger? that we have compiled. Hopefully, through the above content, you have a more detailed understanding of Causes and symptoms of a sulfated battery. Thank you for reading our post.

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