Battery 101: Equalizing Charges

A topic we receive regular questions about is equalizing charges – or the deliberate overcharging of a battery. Since there’s a lot of confusion about what it is, how it affects your battery type, how to do it, and when it should be done, we’ve compiled the basics of an equalizing charge. Let’s jump in.

What is an Equalizing Charge?

An equalizing charge is just another way of describing a deliberate overcharge of the battery, and is part of a proper maintenance routine that should be performed on lead acid batteries.

The purpose is to remove sulfate crystals from the battery plates. Over time the battery plates develop a sulfate coating – which is the number one cause of failure in lead acid batteries. Equalizing the battery also helps fight against stratification.

How Does it Work?

When a battery is given an equalizing charge, it is being overcharged in such a way as to remove (or blow off) the sulfate coating. This allows the surface area of the plates to interact fully with the electrolyte in the battery. It also helps with acid stratification. This is when the acid concentration is greater toward the bottom of the battery.

Stratification occurs over time as the heaviness of the acid causes separation from the water, creating an unequal mixture and reduction in capacity. The equalization charge process causes the electrolytes to bubble – which is great because it  mixes up the acid and creates a more even distribution.

When Should You Perform the Equalizing Charge?

For a 12 volt battery, you should charge it with a minimum voltage of 14.4 volts every 10 discharge cycles for at least one hour. This typically averages out to once per month. There are some manufacturers that suggest the equalization charge needs to only be carried out twice a year or as necessary.

A good rule of thumb is to gauge how often your battery is fully charged. A battery that regularly reaches a full charge will need an equalization charge less frequently compared to a battery that is not used as often. If you experience reduced battery performance, this is a good indication that you may need to give it an equalizing charge.

How Should You Perform an Equalizing Charge?

There are a few things you should keep in mind when equalizing your battery.

First and foremost, do not begin the process and then walk away. You should keep a close eye on the process. If the battery begins to overheat things could go bad – fast. As the battery heats up, hydrogen is emitted. This venting is normal but the hydrogen is very flammable.

If the room is not properly ventilated and the battery gets too hot, the hydrogen could explode. It’s a good idea to keep the room cool and ensure good ventilation before you get started. (Hydrogen only has to reach a concentration of 4% before it becomes explosive so it’s best to have the room properly set up before you start.)

Ok. Now that you’ve got the basics down, keep these pro tips in mind.

Pro Tips:

  • Don’t forget: make sure the battery is fully charged before you begin.
  • Disconnect loads: because you are overcharging the battery, you could damage any equipment that may still be connected.
  • Not all chargers have an equalizing charge setting. Make sure yours does before you begin – if you’re unsure, you can always ask us for help.
  • Check the specific gravity (SG) readings before you begin and then monitor them throughout the process.
  • Only begin equalization if the SG reading shows a difference of 0.030 between the cells.
  • End the charge when the SG reading stops rising.
  • Keep a close eye: monitor the battery temperature and do not allow the battery to become much hotter than 115 degrees Fahrenheit.
  • Patience is a virtue: depending on the amount of sulfation and the battery type, the process could take hours.

Giving your battery an equalizing charge is one of the best forms of maintenance you can do beyond the typical care of keeping the battery clean and storing it in a cool place.

This process can be tedious, time-consuming and, frankly, it can be a bit smelly. Only perform this process if you can do so in a safe manner and have the appropriate equipment. Proper maintenance of your batteries will not only maximize their longevity, but will also maximize their level of performance throughout their life cycle.