Applying an Equalizing Charge

Equalizing Charge for Lead Acid Batteries


You have probably heard of the term "Equalizing charge" but didn't understand what it meant and why it is used or applied. Basically, an equalizing charge is an intentional overcharge that is applied to lead acid batteries in order to remove sulphation or correct a charging imbalance.

applying an equalizing charge

This post will help you understand what this procedure is all about and how this charge may be applied to lead acid batteries. So before we get into the fine details, let's look at the basics.


What is the purpose of an equalizing charge?


Chances are you have a battery but don't know whether or not it needs an equalizing charge. Anyone who has used a lead acid battery for a long time knows too well the importance of equalization. Lead acid batteries are prone to crystallization over time, which is a leading cause of battery failure.


Left unattended, a buildup of crystals can lower the charging capacity and the battery's shelf life. So applying an equalizing charge can help reduce the buildup of crystals and restore the health of your battery.


Applying an equalizing charge can also help you reverse acid stratification. This is where the electrolytes of a battery become concentrated at the bottom.


An equalizing charge can also be used to bring battery cells that are out of balance to a state of equal charge. The charge should correct the imbalance and bring all cells back to a similar level or state.


A charge can also be applied as part of general battery maintenance. Experts often advise the application of equalizing services anywhere from once a month to a couple of times a year. Regular maintenance of this type can be applied to lead acid batteries to prolong its charging capacity and shelf life.


Procedure for Applying Equalizing Charge

Equalizing Charge

Equalizing a battery (new or old) is generally a straight forward procedure. Though the time parameters of equalization vary among manufacturers, the basic steps of equalization are pretty much the same. Here is what normally happens during equalization.


First, the battery is charged fully. Next the battery gravity is measured and, where the difference is more than 0.030, equalization is performed. The typical charge applied is at least 2.5 volts/cell or the equivalent of 15 volts for a 12 volt lead acid battery.


During equalization, gravity checks should be done every hour until the measurements of each cell have equalized.


When applying equalizing charge, it is advisable to keep batteries in a cool environment. Batteries should be constantly monitored for heating or excessive venting. Good ventilation is required to prevent hydrogen buildup.


The Step by Step procedure:

  • Ensure your battery is a flooded lead acid battery
  • Remove all electrical connections to the battery
  • ​Connect the battery to the charger (some chargers will have an equalizing mode)
  • ​Set charger to the equalizing voltage
  • ​Start charging your battery
  • ​Take hourly gravity readings
  • ​Gassing/bubbling of the electrolytes will occur as a result of correct equalizing
  • ​Disconnect the charger when the gravity values stop increasing during the gassing/bubbling phase




When Should I Apply an Equalizing Charge?


If you notice a significant reduction in performance, then that should prompt you to perform equalization. Equalization should be done the first time a battery is purchased (freshening charge) and at least once per month (or after every 10 discharge cycles).


However, some battery manufacturers recommend that an equalizing charge be applied every month. It’s best to inquire or find out what the manufacturer has recommended for your particular battery type.


Final Thoughts


Equalizing your lead acid batteries is a fantastic way of prolonging its shelf life and preventing any unwanted operational costs. This procedure will also reduce the formation of lead sulphate crystals on the plates, a common problem that shortens the life of batteries.


If you do it from time to time, you will be able to maintain the charging capacity and power of your battery.


Note: Applying an equalizing charge will cause gassing & bubbling of the electrolytes. Make sure you replace lost water during this process.


The complete guide to this procedure can be found in the battery reconditioning guide.


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