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My Forklift Battery Smells Like Rotten Eggs

Written by editor on May 12, 2012 – 11:54 am - (19999 views)

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It is the start of the day and standing at your door way is your lead hand with something urgent to say,  “Boss, we have a problem.  One of the forklift batteries smells like rotten eggs.  What do we do?”

Forklift batteries, when charging, should not smell like rotten eggs. The slightly acrid acid smell of a charging (gassing) battery is normal, but if the lift truck battery smells of rotten eggs, there is a problem.

The Rotten Eggs Smell is Sulfur

As you know, forklift batteries are made from lead plates, covered in lead oxide paste, in a bath of sulfuric acid.

When one of the cells in your forklift battery stops accepting a charge, the forklift battery charger stubbornly continues to charge the cell, hoping to bring the cell up to full voltage.  The cell gets hot and starts to boil off the acid inside.  Baked sulfuric acid smells like rotten eggs.

Rotten Eggs Smell is Coming From IC Lift Truck or Car

If the battery is in an internal combustion (IC)  forklift, or a car, it is possible for the alternator to be overcharging the battery and become the source of the rotten eggs smell.   Don’t replace your battery a second time needlessly – have your alternator checked when you replace your stinky battery.

Forklift Battery Smells Like Rotten Eggs – What do I do?

Forklift batteries are different to car batteries.  They are bigger, heavier (1600 lbs to 3000 lbs) and more expensive.  If your battery is smelling like rotten eggs while on charge, this is what you do:

  1. Turn off the charger
  2. Let it cool down
  3. Do not used the battery – red tag it!
  4. Call in a professional battery and charger company
  5. Replace the defective cell or battery
  6. Check your charger is working properly


What Happened?  Why did the Forklift Battery Fail?

So you are probably wondering what happened to the battery for the cell to fail.  Assuming the problem is not your charger, what happened is one of the 12, 18 or 24 cells in your forklift battery shorted out.

Bad Warehouse Floor

One of the causes can be the jarring of the forklift of the electric forklift on a rough, uneven floor.  Constant jarring knocks the paste off the forklift battery plates causing them to short out prematurely.  When the bottom of the cell fills with loose lead oxide shed from the sides of the battery plates, a circuit can be created causing the battery cell to “short out”.


Another cause could be the quality of the water used to water the forklift  battery.  If the water you are adding after charging the battery is full of dissolved minerals, those minerals can accumulate and make it difficult to charge the battery.  The cell can overheat and send an eggy smell throughout the warehouse.

Battery Manufacturer’s defect

Of course, sometimes a battery cell can reverse polarity because the wraps around the cell tear prematurely, shedding material and shorting the cell.  Check with your battery manufacturer for warranty repairs.

Egg smell coming from a forklift battery - Sulfur

Rotten egg smell from your forklift?

Forklift batteries are generally warrantied for a minimum of 3 years and up to 6 or 7 years.  A manufacturer’s defect is going to show up early or in at least in the first year.  After that your  lift truck battery will likely work reliably until it simply wears out.  The warranty period provided after 3 years is often offered as a “short life credit” and is designed to keep you purchasing the same brand of forklift battery.  If your large forklift battery is lasting less than 8 years, check your battery charging, maintenance and watering practises.

Replacement Forklift Battery

Be sure in the process of repairing a lift truck battery to budget for a new battery.  You may be able to repair the battery, especially if the battery is less than 3 years old, but if the battery is older than that and has a cell that has failed, you are likely looking at another cell failing shortly afterwards.  Do not keep pumping money into a failing battery.  A failing battery will:

  • Run hot
  • Run out of juice before the end of the shift
  • Pull too many amps through forkilft components increasing the need for forklift repairs
  • Consume more electricity to charge

Here are some popular brands of replacement forklift batteries in alphabetical order:


Did we cover everything?  Do you agree with the advice offered?  Did we include your favorite battery manufacturer?  Please post comments below.

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Posted in Battery Charger, Battery Maintenance, Electric Forklift, Forklift Battery, Forklift Battery & Charger, Lift truck, Warehouse Basics | Comments Off on My Forklift Battery Smells Like Rotten Eggs

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