Charging Lead Acid Batteries

When it comes to effectively charging a battery, end users should be aware of some common mistakes.

Contrary to what many believe, a battery should never run until it is “out of juice,” or “dies.” Manufacturers say operators should check battery discharge indicators included on most floor equipment and return the machine to the charging dock well before it dies. Instead batteries should discharge to about 25 percent, though this rate varies among battery suppliers. The discharge rate may also differ for new batteries, Bohlman says.

“With new batteries, you need to be careful not to discharge more than 60 percent,” says Bohlman. “Some people will use them excessively until 90 percent (discharged) and plug them in. It takes approximately 20 charging cycles until you can use the batteries to their full capacity.”

Users should also be careful not to overcharge a battery. This happens when a battery is charged for an extensive period of time, such as over a weekend, Ghen says, something many end users mistakenly believe is the solution for a battery that isn’t performing to its full capacity.

When a battery is overcharged the hydrogen created during gassing can result in bloating, or worse, can make a battery explode. Consequently, batteries should never be charged in temperatures above 120 degrees — or in temps below 32 degrees, for that matter, when the electrolyte can turn to ice and expand.

If the person performing maintenance suspects a malfunctioning battery they should first try to equalize the battery.

 According to manufacturers, equalization is a controlled overcharge that helps remove sulfate crystals that may be built-up on plates, and reverses other chemical effects such as stratification. This overcharge is conducted after a battery has already been fully charged.

Most battery chargers have an equalization mode on the dashboard. Users simply place the setting to equalization, and monitor voltage readings every hour until the voltage stops rising using a handheld voltmeter.

A person can also use a hydrometer to gauge gravity levels inside the cell (which indicates the presence of sediment), but this step is more than often left to the equipment servicer, and technical.

Once a battery is charging, the charge cycle should never be interrupted.