What is a Sulfated Lead Acid Battery - Things You Should Know

Invented in 1859, lead acid batteries are the most widely used rechargeable battery due to their high power density and power-to-weight ratio. However, with time, lead-acid batteries undergo a sulfation process when the electrolyte begins to break down, leading to the separation of sulfuric acid and the formation of sulfur ions, decreasing the battery's overall efficiency and storage capacity. 

 

So, what exactly is lead acid battery sulfation? In this blog, we will explore the science behind sulfation and its effects on lead-acid batteries, as well as tips for preventing and treating sulfation to help prolong the life of your batteries.

What Is Sulfation in Lead Acid Battery?

Sulfation is common in lead-acid batteries that can drastically reduce their efficiency and lifespan. As the electrolyte in the battery begins to break down, the sulfuric acid separates, releasing sulfur ions that combine to form crystals. These crystals then adhere to the lead plates, forming lead sulfate crystals that can grow in size and harden over time, eventually covering the plates entirely. 

Sulfation can grow in size over time, just like salt crystals, and this can obstruct the negative active material, preventing it from participating fully in the battery reactions. This buildup can severely diminish the battery's power storage capability and overall efficiency, ultimately leading to failure if left untreated.

What Causes a Sulfated Battery?

Sulfation is unavoidable in all lead-acid storage batteries, as sulfate is formed each time the battery is discharged and recharged. However, certain factors can accelerate the sulfation rate and shorten the battery's lifespan. Overcharging or undercharging and leaving the battery discharged for even a few days can rapidly increase sulfate buildup. Even storing a fully charged battery can lead to sulfation unless a desulfation battery charger is used. Moreover, high temperatures above 75°F can significantly increase the self-discharge rate and sulfation rate. For every 10°F rise in room temperature, the rate of sulfation is increased up to 2x times.

Signs of Lead Acid Battery Sulfation

When a lead-acid battery starts to sulfate, it may display a range of signs indicating it needs attention. Some common symptoms of lead acid battery sulfation are:

• Early gassing
• Poor charge acceptance and higher charging voltage
• Fall in battery capacity
• Chunky shedding and bulking of active material
• Plate discolouration and gritty/sandy feeling to the touch

Common Reasons for Lead Acid Battery Sulfation

There are several common reasons for battery sulfation, including:

 

• If a battery is left unused for an extended period, sulfate crystals can form on the lead plates. In hotter climate regions, sulfation starts in 24 hours, and in colder regions, it starts after a few days.
• If a battery is stored without being connected to a charger or other energy source, it can develop sulfation.
• Undercharging a battery to just 90% of its capacity can leave 10% of the battery inactive, allowing sulfation to occur. Additionally, incorrect charging settings can contribute to sulfate buildup.
• When the electrolyte level in a battery is low and the plates are exposed to air, sulfation can occur quickly.

How to Reverse Lead Acid Battery Sulfation?

Two types of sulfation may occur in lead sulfate batteries: Permanent and Reversible. Reversible sulfation may be reversed if detected early, but it should only be attempted by someone with experience working with lead-acid batteries, such as the retailer where the battery was purchased. On the other hand, permanent sulfation can't be reversed and requires battery replacement.

Permanent Sulfation

Permanent sulfation occurs when a battery remains in a low charge for an extended period, typically weeks or months. Although restoration is sometimes possible, it is unlikely and often requires battery replacement.

Reversible Sulfation

There is a simple solution to reverse reversible sulfation in a lead battery. An overcharge can be applied to a fully charged battery with a 200mA regulated current. The battery terminal voltage should be raised to 2.50V and 2.66V per cell (15V and 16V on a monoblock of 12V) for approximately 24 hours. Additionally, increasing the battery temperature to 50°C to 60°C (122 to 140°F) at the time of corrective service helps to dissolve the crystals effectively.

While anti-sulfation devices can prevent and reverse sulfation on healthy batteries by applying pulses to battery terminals, they may not be able to reverse the damage entirely and are not always recommended.

How to Prevent Lead Battery Additive Sulfation?

Preventing battery sulfation is essential to extending the lifespan and maintaining the efficiency of lead-acid batteries. Proper storage is one of the easiest ways to prevent battery sulfation. Even when stored at a full charge, a battery must be charged enough to prevent it from dropping below 12.4 volts, as applying this maintenance charge will prevent sulfates from building up. Additionally, it's crucial to note that storing batteries in temperatures above 75 degrees Fahrenheit accelerates the rate of self-discharge and doubles the sulfation rate for every 10 degrees above room temperature.

Performing regular battery maintenance and following charging best practices are simple steps to prevent sulfation. Once sulfation has occurred, reversing the effects is highly unlikely, making it even more critical to take care of your batteries from the start. Don't wait until it's too late - start preventing sulfation today to prolong the life and performance of your batteries.

Note: Many believe disconnecting a battery will prevent sulfation, but unfortunately, this is just a myth. Disconnecting the battery may avoid discharge trickle, but it does not prevent the electrolyte from breaking down inside the battery. While it may help slow down the process of battery sulfation, it will not prevent it from ultimately occurring.

Conclusion

Batteries have become integral to our daily lives, powering our devices and vehicles. Replacing a battery increases the maintenance charge. Therefore, it is vital to ensure proper battery charging to extend the life of your investment. Regularly charging your battery can prevent premature failures and avoid the common issue of battery sulfation. 

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