How Lead-Acid Forklift Batteries Work

Last year, electric forklifts accounted for 64% of the US forklift market; so far, part (or all) of your fleet may be powered by lead-acid batteries.

If you are accustomed to seeing electric forklifts sliding around the facility every day, it is easy to take its power source for granted. However, lead-acid forklift batteries deserve detailed consideration. This is a fascinating technology, and understanding the basic science behind forklift batteries will help you implement effective battery maintenance procedures and improve the efficiency of your entire fleet.

Lead-acid forklift battery on charging standLead-acid forklift batteries provide voltage between two output terminals with a series of electrochemical reactions. Here’s how the process works:

Three substances interact within the cell of a lead-acid forklift battery:

Plates of lead dioxide.

Plates of pure, soft lead called “spongy lead.”

An electrolyte mixture of sulfuric acid and water.

The alternating plates of each battery cell contain layers of lead dioxide and spongy lead. When acidic electrolytes come into contact with these compounds, complex chemical reactions can create an electronic imbalance between the two types of plates. Electrons naturally flow from the negative plate to the positive plate, trying to correct the imbalance of subatomic particles.

All lead dioxide plates are connected to a positive terminal, while the spongy lead plate is connected to the negative terminal. These terminals constitute an external circuit. If we connect a terminal to a conductor (for example, the power system of a forklift), electrons will move from one terminal to the other through the conductor. This is how we use the voltage generated by the battery’s chemical reaction.

The forklift battery charger reverses the process with a steady voltage flow. The energy from the charger converts the lead sulfate back to its original form, thereby increasing the specific gravity of the sulfuric acid present in the electrolyte. This prepares the battery to restart the discharge process. This is not like filling a gas tank, but like evaporating and condensing the same glass of water again and again.

Chemical Reactions and Forklift Battery Maintenance

Like any chemical reaction, the interaction between sulfuric acid, water, and lead also produces new substances. If left unchecked, these substances will limit the efficiency of the battery and even damage the battery itself.

Lead sulfate and water are generated when forklift batteries are discharged. The growth of lead sulfate is called sulfation, which reduces the efficiency of the battery. Regular washing in a dedicated battery washing cabinet can help remove powdered lead sulfate that has accumulated on the terminals. Washing can also remove leaking electrolyte and prevent unnecessary discharge.

The discharge of a forklift battery also converts a large amount of electrolyte into water, which is then decomposed into hydrogen and oxygen molecules. As these molecules escape, the water level in the battery cell will drop. This is dangerous to the board; if the printing plates are exposed to air, they will oxidize and lose capacity permanently.

Under certain conditions, the battery will also release hydrogen and oxygen during the charging process. This is the so-called “venting”, which is why the ventilation requirements for lead-acid batteries in the battery replacement area are so strict. Outgassing can also cause moisture loss. Develop a strict schedule to monitor the battery and replace the water when necessary. Consider installing an integrated watering system to automatically water the entire battery pack after the charging process is complete.

Don’t worry about maintenance tasks starting to become onerous. A battery fleet management system (such as BHS Fleet Tracker) can help you proceed as planned. It is also helpful to train employees on the details of how the electric forklift battery actually works-it is always easy to follow the maintenance schedule when you fully understand what is inside the battery box.