How to Repair Your Forklift Battery

Forklift batteries are similar to the lead acid batteries seen in cars, albeit those used to run forklifts are much larger, heavier, and more difficult to repair or refurbish.  Unlike car batteries, forklift batteries are deep-cycle batteries and can therefore be discharged to lower levels without causing damage.  While there are number of DIY steps that forklift users can take themselves to work on batteries like cleaning, replacing fluids, and removing sulfation. That being said, extensive refurbishment is best left to professionals who can apply both experience and equipment to the task.

Battery Exam: Troubleshooting and Common Problems

When a forklift isn’t behaving properly, one of the best places to start looking is the battery, as any number of problems here will almost immediately begin effecting the performance of the machine.  Taking the steps to repair a battery should be done with batteries that are performing below 80 percent rated capacity; it is almost identical to repairing a car battery. You should remember that your car dealer is responsible for the technical state of your car.

Low Water Levels

One of the most common reasons for battery failure is low water levels and can even lead to irreparable damage.  When the battery dries, the uppermost portion of the ‘plates’ begin to burn, leaving permanent high resistance and isolating the submerged portion.  Even if water levels are restored, the damage continues to cause problems, accelerating water loss and causing a higher rate of overheating.

To prevent drying and overheating, add water before or after cleaning, but just enough to cover the perforated splash guard.  Be sure not to overfill. Using a hydrometer to measure if the fluids are 30 percent sulfuric acid and 70 percent water is also important.

Overcharging & Opportunity Charging

At bare minimum, industrial batteries should last 1,500 charge cycles in a five-year period and every time the battery is charged, regardless of time, counts as one cycle.  Unless the battery needs charging it should be left alone though many people make the mistake of opportunity charging during a lunch break, cutting the battery life by 50 percent or regularly charging before it’s been discharged 80 percent.

Over Watering

This washes out electrolytes from cells, dilutes the acid, and causes corrosion till the battery is no longer useful.  It can however be slightly mitigated by adjusting the acid, though battery life is still shortened.  Acid adjustments should not be undertaken by individuals.

Failing to Equalize Charge

Equalizing should be done once every two weeks and can be done using the chargers Equalize feature. It also should not be done more than once every 5th charge cycle or the battery will get damaged as doing it too frequently reduces battery life. Equalizing adds 3 hours to charge time.


Washing and rinsing the battery yearly helps prevent corrosion as acid vapors regularly escape during charge and cause corrosion. Check battery, cables, and connectors for corrosion only while the battery is disconnected.  If any cables come loose they need to be fixed.


While servicing the battery never wear any metal objects, never smoke or have flames near the battery, and always wear eye protection. Carry out work in a well ventilated area and make sure the forklift is shifted off. Making sure to follow proper forklift safety and maintenance guidelines is always recommended when doing any work on heavy machinery.

Beyond Repair

In some instances there is nothing that can be done and a battery has been irreparably damaged. Normally this is around the 5 year mark when positive plates soften and expand in size, causing internal pressure inside the cells. Some batteries that fall can also sustain damage that can’t be fixed.

About Tom Reddon

Tom has been involved in the forklift industry since 1986. He loves doing research, blogging, and speaking about forklifts. You can contact Tom on his Twitter or Google+ profiles.

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