Types of forklift batteries – Different batteries explained

Charging a forklift battery

Lead-acid batteries (forklift batteries) are fairly slow to recharge and must be stored in a fully charged state.  Charging is required every 30 days to avoid sulfation, which can rob the battery of its ability to be recharged.

Preventing damage to a forklift battery

Another condition to be careful to avoid is deep-cycling.  When a battery is deeply discharged, the strain shortens its life.  Attention should be paid to keep the battery above the lower discharge limit.  Many forklifts will prevent overdischarge by showing 0% charge when the battery is at 20%.

Life expectancy for a lift truck’s battery

Forklift lead acid batteries usually have work life of 1500 cycles or more.  Maintaining charging and watering records will help you to collect on your manufacturers warranty.  Battery companies can check how the battery was charged, watered and discharge by using a destructive cell analysis that will show grid corrosion, depletion of active material from the grid inside the cell and positive plate growth.  With photographs of the damage, a larger or smaller short life credit will be offered to encourage you to purchase another battery of the same brand.  Good records will increase your negotiating position.

How heavy is a forklift battery?

Though lead-acid batteries have a low energy density compared to other battery technologies, due to the weight of the lead, they provide an important source of ballast.  A typical 3000 lbs capacity reach truck needs at least 1900 lbs of ballast weight to counterweight the load being lifted.  Lead-acid batteries, therefore provide more than just a rechargeable energy supply but are integral in the safe operation of the forklift.

Plate thickness and ballast weight

More than just for ballast, the weight of a battery can predict the service life of a battery.  Because a thicker positive plate has more active material to corrode and shed as sediment to the bottom of the battery, the weight of a battery is a good indication of the lead content and therefore the life expectancy.  Ask your battery supplier for the weight of their battery to help compare value for money.

Forklift batteries have plates that exceed 1/4” (6mm).  Most industrial flooded deep-cycle batteries use lead-antimony plates that improves the plate life but increases gassing and water loss.

Sealed lead-acid forklift battery

Maintenance-free batteries are a popular option for use in controlled working environments such as pharmaceutical manufacturing.  pallet trucks (electric pallet jacks) as they can operate in any position.  The acid inside the forklift battery is made into a gel and sealed inside the cell.  Valved cell caps allow for venting during charging.  The loss of moisture shortens the life of the maintenance-free battery over time.  Many manufacturers recommend operating the battery always above 40% discharge but below 80% discharge to extend the life of the battery.  These types of batteries do not last long when deeply discharged or over-charged.

Temperature of forklift battery

The optimum operating temperature for the lead-acid battery is 25*C (77*F). Higher temperatures reduce longevity. As a guideline, every 8 degrees Celsius (15 degrees F) rise in temperature will cut the battery life in half. A valve-regulated lead-acid battery, which would last for 10 years at 25C (77F), will only be good for 5 years if operated at 33C (95F). Theoretically the same forklift battery would last a little more than one year at a desert temperature of 42C (107F).

Absorbed Glass Mat Batteries (AGM) for forklifts

German high performance cars us AGM batteries due to their durability and ability to endure extensive shock and vibration.  This technology is sealed and maintenance free, however are almost twice the cost of flooded lead-acid batteries.  By using absorbed glass mats between the plates, the batteries recombine the oxygen and hydrogen inside the cells and lose almost not water.

Pros and Cons of Lead-Acid forklift batteries

Pros

• Inexpensive and simple to manufacture.
• Mature, reliable and well-understood technology – when used correctly, lead-acid is durable and provides dependable service.
• The self-discharge is among the lowest of rechargeable battery systems.
• Capable of high discharge rates.

Cons

• Low energy density – poor weight-to-energy ratio limits use to stationary and wheeled applications.
• Cannot be stored in a discharged condition – the cell voltage should never drop below 2.10V.
• Allows only a limited number of full discharge cycles – well suited for standby applications that require only occasional deep discharges.
• Lead content and electrolyte make the forklift battery environmentally unfriendly.
• Transportation restrictions on flooded lead-acid – there are environmental concerns regarding spillage.
• Thermal runaway can occur if improperly charged.

For a great resource on various types of battery technologies, please visit: http://batteryuniversity.com