Maintaining lead-acid batteries: the importance of equalization charge

Lead-acid batteries are widely used in a variety of applications, ranging from stationary energy storage systems to vehicles. They provide a reliable and cost-effective solution for many energy storage requirements.

An essential maintenance procedure for lead-acid batteries is the application of a so-called equalization charge.

What is an equalization charge?

An equalization charge is a controlled overcharge in which the battery voltage is increased to approximately 2.50 V per cell. This process is intended to address two common issues in lead-acid batteries:

• Sulphation: over time, sulphate crystals can accumulate on the battery plates. An equalization charge helps break down and remove these crystals.
• Acid stratification: this occurs when the acid concentration inside the battery becomes unevenly distributed. The equalization process helps mix the electrolyte evenly throughout the cells.

➜ Also read more about the advantages of lead-acid batteries

When and how often should an equalization charge be performed?

In general, it is recommended to perform an equalization charge anywhere from once a month to twice a year, depending on battery usage and manufacturer recommendations.

A more accurate method is to fully charge the battery and then measure the specific gravity (SG) of the electrolyte in each cell using a hydrometer. If the SG difference between cells exceeds 0.030, an equalization charge may be necessary.

Equalization charging process: important considerations

During the equalization process, it is important to monitor the SG values hourly and disconnect the charger once the SG values stop increasing.

Ensure that the battery remains properly cooled and is continuously supervised during charging. Hydrogen gas released during overcharging is highly flammable. Always charge batteries in a well-ventilated area.

Equalization charging for VRLA and other sealed batteries

Equalizing Valve Regulated Lead Acid (VRLA) batteries requires extra caution. Since VRLA batteries are generally sealed and do not provide access to the electrolyte, direct measurement is usually not possible.

It may nevertheless be advisable to apply an equalization charge periodically, typically once a month for a duration of approximately 2 to 16 hours, depending on manufacturer specifications.

An equalization charge plays an important role in maintaining the performance and lifespan of lead-acid batteries. Always follow the battery manufacturer’s recommendations and apply the appropriate safety precautions.

Let Elfa advise you

Are you looking for the right lead-acid battery for your application or industry? Explore the available range in our catalog or contact the experts at Elfa for professional advice.