Forklift Batteries

The battery is the heart of any electric forklift. It provides the energy to lift loads, drive the truck, and power all onboard systems. Choosing the right battery technology, sizing it correctly, and maintaining it properly can mean the difference between a productive fleet and one plagued by downtime and unexpected costs.

Electric forklifts have become the dominant choice in warehouses, distribution centres, and manufacturing plants worldwide. They produce zero direct emissions, run quietly, and in many applications cost less to operate than internal combustion alternatives. But their performance depends entirely on the battery pack sitting in the compartment beneath the operator.

This guide covers the main battery technologies used in forklifts today, explains how to size and select a battery, and walks through the practical realities of charging, maintenance, and eventual replacement. Whether you manage a single truck or a fleet of hundreds, understanding forklift batteries will help you make better decisions and avoid costly mistakes.

Why battery choice matters

A forklift battery is not a minor accessory. In a typical electric counterbalance forklift the battery accounts for a significant portion of the vehicle weight, often between 800 and 2500 kilograms depending on truck size. This mass serves a dual purpose. It stores energy and it acts as counterweight to balance loads on the forks.

Battery selection affects

How many hours the truck can work before it needs charging or a battery swap
How quickly you can return the truck to service after a break
How much floor space and infrastructure you need for charging areas
The total cost of ownership over the life of the forklift
Safety risks including hydrogen gas, acid spills, and thermal events

Getting this decision right up front saves money and headaches for years to come. Getting it wrong can leave you with trucks that cannot finish a shift or charging systems that cannot keep up with demand.

Lead acid batteries

Lead acid batteries have powered electric forklifts for over a century. They remain the most common choice in many markets because the technology is mature, widely understood, and relatively inexpensive to purchase.

How lead acid batteries work

A lead acid battery contains cells made of lead plates immersed in a sulfuric acid electrolyte. When the battery discharges, a chemical reaction between the lead and the acid releases electrons that flow through the external circuit to power the forklift motors. Charging reverses the reaction, restoring the plates and electrolyte to their original state.

Each cell produces about 2 volts. Forklift batteries stack cells in series to reach common system voltages of 24, 36, 48, or 80 volts. A 48 volt battery contains 24 cells. An 80 volt battery contains 40 cells.

Flooded lead acid

Flooded lead acid batteries, sometimes called wet cell batteries, are the traditional design. The electrolyte is liquid sulfuric acid that covers the plates. During charging, water in the electrolyte breaks down into hydrogen and oxygen gas which escapes through vents in each cell cap.

This gassing means flooded batteries require regular watering. Operators or maintenance staff must check electrolyte levels and add distilled or deionised water to keep plates covered. If water levels drop too low, plates become exposed and suffer permanent damage. If batteries are overfilled, acid can overflow and corrode surrounding components.

Flooded batteries also produce hydrogen gas during charging. Hydrogen is flammable and can create explosion risk if it accumulates in poorly ventilated spaces. Charging areas for flooded batteries must have adequate ventilation and prohibit open flames and sparks.

Despite these demands, flooded lead acid batteries offer the lowest purchase price per kilowatt hour of capacity. For operations that can manage the maintenance requirements, they remain a cost effective choice.

Sealed lead acid and AGM

Sealed lead acid batteries, including absorbed glass mat (AGM) designs, contain the electrolyte in a form that does not spill if the battery tips over. Gas produced during charging recombines internally under normal conditions, so these batteries need no watering and produce less hydrogen.

AGM batteries cost more than flooded designs but reduce maintenance labour and simplify ventilation requirements. They are popular in smaller forklifts, walkie stackers, and electric pallet jacks where compact size and reduced maintenance matter more than absolute lowest cost.

Lead acid battery lifespan

A well maintained flooded lead acid forklift battery typically delivers between 1000 and 1500 charge cycles before capacity drops below useful levels. At one cycle per day this translates to roughly four to six years of service. Poor maintenance, deep discharges, high temperatures, and fast charging can shorten life significantly.

Signs of an aging lead acid battery include reduced run time, slower acceleration, longer charging times, and cells that boil excessively during charging. When capacity falls below about 80 percent of original, most operations replace the battery.

Lithium ion batteries

Lithium ion batteries have transformed consumer electronics and electric vehicles over the past two decades. They are now making rapid inroads into the forklift market, offering advantages that suit high intensity operations.

How lithium ion forklift batteries work

Lithium ion batteries use lithium compounds in the cathode and typically graphite in the anode, with a liquid or gel electrolyte carrying lithium ions between them. Different cathode chemistries exist, but lithium iron phosphate (LFP) dominates the forklift market because it offers excellent safety, long cycle life, and tolerance for demanding duty cycles.

Unlike lead acid cells at 2 volts each, lithium ion cells produce about 3.2 volts for LFP chemistry. Fewer cells are needed to reach a given voltage, and packs include a battery management system (BMS) that monitors cell voltages, temperatures, and state of charge to protect the pack and optimise performance.

Advantages of lithium ion

Lithium ion batteries offer several compelling benefits for forklift applications

Opportunity charging. Lithium ion packs can be charged during breaks, lunch periods, and shift changes without damaging the battery. This eliminates the need for battery swaps in many operations and means one battery can power a truck through multiple shifts.
Fast charging. Many lithium ion forklift batteries can charge from 20 to 80 percent in about an hour. Some systems offer even faster rates. This speed keeps trucks productive with minimal downtime.
No watering or equalisation. Lithium ion batteries are sealed and require no electrolyte maintenance. There is no hydrogen gassing under normal operation, so ventilation requirements are simpler.
Flat discharge curve. Lithium ion batteries deliver consistent voltage and power throughout most of the discharge cycle. Forklifts feel strong and responsive even as the battery approaches empty, unlike lead acid where performance fades as charge drops.
Longer cycle life. Quality lithium iron phosphate packs can deliver 2500 to 4000 cycles or more. This can translate to a decade or longer of service in typical applications, potentially outlasting the forklift itself.
Reduced weight for same energy. Lithium ion batteries store more energy per kilogram than lead acid. However, forklift designers often add ballast to maintain proper counterweight, so weight savings may not always apply.

Disadvantages and considerations

Lithium ion batteries are not without drawbacks

Higher upfront cost. A lithium ion forklift battery typically costs two to three times as much as an equivalent lead acid pack. The total cost of ownership may be lower over time, but the initial investment is significant.
Temperature sensitivity. Lithium ion batteries perform best in moderate temperatures. Extreme cold reduces capacity and charging speed. Extreme heat accelerates degradation. Some packs include heating or cooling systems to manage this.
Infrastructure changes. Chargers designed for lead acid batteries cannot charge lithium ion packs. Converting a fleet requires new chargers and possibly electrical upgrades.
Thermal runaway risk. Although rare with LFP chemistry, lithium ion batteries can experience thermal runaway if damaged or improperly managed. The BMS provides protection, but proper handling and maintenance remain important.

When lithium ion makes sense

Lithium ion batteries deliver the greatest return in operations with

Multi shift use where battery swapping would otherwise be needed
Limited space for battery rooms and charging infrastructure
High utilisation rates that reward fast opportunity charging
Cold storage applications where opportunity charging avoids moving batteries in and out of freezers
Long planning horizons where lifecycle cost matters more than purchase price

Other battery technologies

While lead acid and lithium ion dominate the market, other technologies appear in specialised applications.

Nickel iron batteries

Nickel iron batteries, sometimes called Edison batteries after their inventor, use nickel oxide hydroxide cathodes and iron anodes in an alkaline electrolyte. They are extremely durable and can last 20 years or more with proper care.

However, they are heavy, inefficient compared to modern alternatives, and produce hydrogen during charging. They see limited use in forklifts today but remain popular in some stationary and off grid applications where extreme longevity outweighs other factors.

Nickel cadmium batteries

Nickel cadmium (NiCd) batteries offer good performance in extreme temperatures and tolerate deep discharges well. They were once common in European forklift fleets, particularly in cold storage.

Environmental concerns about cadmium have reduced their popularity, and lithium ion now offers similar or better cold weather performance without the toxic heavy metal. NiCd batteries are still available but increasingly rare in new installations.

Hydrogen fuel cells

Hydrogen fuel cells generate electricity by combining hydrogen gas with oxygen from the air. The only byproduct is water. Fuel cell forklifts refuel in minutes, similar to filling a propane tank, and can run continuously through long shifts without battery swaps or charging breaks.

Major companies including Amazon, Walmart, and BMW have deployed fuel cell forklift fleets in large distribution centres. The technology works well in high throughput operations where battery charging would create bottlenecks.

Challenges include the cost of hydrogen, the need for on site hydrogen storage or generation, and the higher purchase price of fuel cell systems. Infrastructure requirements limit adoption to large operations that can justify the investment.

Battery specifications and sizing

Selecting the right battery requires matching specifications to your forklift and operational demands.

Voltage

Forklift batteries come in standard voltages that must match the truck design. Common voltages include

Voltage	Typical applications
24V	Walkie pallet jacks, small stackers, light duty trucks
36V	Three wheel sit down forklifts, walkie stackers, some pallet trucks
48V	Four wheel counterbalance forklifts, reach trucks, order pickers
80V	Large counterbalance forklifts, heavy duty applications

Installing a battery with the wrong voltage can damage the forklift electronics or fail to provide adequate power. Always verify voltage requirements before ordering.

Capacity

Battery capacity is measured in ampere hours (Ah). A 1000 Ah battery can theoretically deliver 1000 amps for one hour, or 100 amps for 10 hours, or other combinations that multiply to the same total.

Higher capacity means longer run time between charges. Common forklift battery capacities range from about 200 Ah for small pallet jacks to 1500 Ah or more for large counterbalance trucks working heavy loads through full shifts.

To estimate required capacity, consider

How many hours per shift the forklift operates
The average power draw based on load weights and travel distances
Whether opportunity charging is available during breaks
A safety margin of 20 to 30 percent to avoid deep discharges

Forklift manufacturers and battery suppliers can help calculate requirements based on your specific application.

Physical dimensions and weight

Batteries must fit the forklift compartment and meet minimum weight requirements for counterbalance. Compartment dimensions vary by forklift model, and batteries are built to match standard sizes.

If you are replacing a lead acid battery with lithium ion, the new pack may weigh less. Some lithium ion batteries include ballast to maintain proper truck balance. Others require separate counterweight additions. Verify that the total installed weight meets the forklift manufacturer specifications.

Charging systems and infrastructure

The charger and charging area are as important as the battery itself. Poor charging practices shorten battery life and create safety hazards.

Charger types

Forklift battery chargers fall into several categories

Conventional chargers deliver a fixed charging profile over 8 to 12 hours. They suit single shift operations where batteries charge overnight.
High frequency chargers use solid state electronics to deliver more efficient charging with less heat. They are smaller, lighter, and often more energy efficient than conventional designs.
Opportunity chargers deliver high current to quickly add charge during breaks. They work with batteries designed for partial charging and are essential for multi shift operations without battery swaps.
Fast chargers push even higher currents for rapid charging. They require batteries specifically designed for fast charging and generate more heat.

Lithium ion batteries require chargers designed for their chemistry and communication protocols. Lead acid chargers will not work with lithium ion packs and attempting to use them can cause damage or safety incidents.

Charging area requirements

Lead acid battery charging areas need

Adequate ventilation to disperse hydrogen gas, typically 1 cubic foot per minute per cell during charging
Eye wash stations and spill containment in case of acid exposure
No smoking signs and prohibition of open flames and sparks
Electrical capacity to run multiple chargers simultaneously
Space for battery handling equipment if swapping batteries between trucks and charging stations

Lithium ion charging areas have simpler requirements since there is no gassing or acid exposure. However, they still need appropriate electrical capacity and fire safety measures.

Battery changing equipment

Operations that swap batteries between trucks and charging stations need equipment to handle heavy packs safely. Options include

Battery extractors that pull and insert batteries from the side of the forklift compartment
Overhead cranes with spreader bars for top loaded compartments
Transfer carts that carry batteries between trucks and charging racks
Roller stands and conveyor systems for high volume battery rooms

Handling equipment must match battery weight and compartment design. Dropping a battery or misaligning it during insertion can cause serious injury and equipment damage.

Battery maintenance

Proper maintenance extends battery life and prevents costly failures. Requirements differ by battery type.

Lead acid maintenance

Flooded lead acid batteries need regular attention

Watering. Check electrolyte levels weekly and add water as needed. Water only after charging when levels are at their lowest reading point. Use distilled or deionised water only.
Equalisation. Periodic equalisation charges at higher voltage help balance cell voltages and prevent stratification of the electrolyte. Follow the battery manufacturer schedule, typically every 5 to 10 cycles.
Cleaning. Keep battery tops clean and dry. Acid residue and dirt can create conductive paths that drain the battery. Neutralise acid with baking soda solution and rinse with clean water.
Connection inspection. Check cable connections for corrosion and tightness. Loose or corroded connections cause resistance, heat, and power loss.
Temperature monitoring. High temperatures accelerate degradation. If batteries run hot, investigate causes such as overcharging, excessive discharge rates, or inadequate ventilation.

Lithium ion maintenance

Lithium ion batteries require less routine maintenance but still benefit from attention

Keep connections clean. Inspect charging contacts and power connections regularly.
Monitor BMS alerts. The battery management system tracks cell health and will flag problems. Investigate any fault codes promptly.
Avoid extreme temperatures. Park trucks in moderate conditions when possible. If batteries include heating or cooling systems, ensure they function correctly.
Follow charging guidelines. While opportunity charging is allowed, some manufacturers recommend occasional full charges to help the BMS calibrate state of charge readings.

Common problems and solutions

Problem	Possible causes	Solutions
Reduced run time	Aging cells, low water, sulfation, BMS fault	Test capacity, check water levels, perform equalisation, inspect BMS
Slow charging	Charger fault, high temperature, connection resistance	Test charger output, improve ventilation, clean connections
Excessive heat	Overcharging, high discharge rates, internal shorts	Verify charger settings, reduce duty cycle, test for shorts
Leaking acid	Cracked case, overfilling, damaged cells	Inspect case, adjust watering procedure, replace damaged cells

Cost considerations

Battery costs extend well beyond the purchase price. A complete analysis includes

Initial investment

Lead acid batteries typically cost between 3000 and 15000 euros depending on voltage and capacity. Lithium ion packs for the same applications range from 8000 to 35000 euros or more. Hydrogen fuel cell systems are even more expensive initially.

Charging infrastructure

Chargers cost from a few hundred euros for small units to several thousand for high frequency or fast chargers. Electrical upgrades to support multiple chargers can add significant expense. Hydrogen operations require storage tanks, dispensers, and either delivered hydrogen or on site generation equipment.

Maintenance labour

Lead acid batteries need regular watering, cleaning, and inspection. This labour cost adds up over years of operation. Lithium ion batteries reduce maintenance labour significantly. Fuel cells require periodic stack inspections and filter replacements.

Energy costs

Charger efficiency affects how much electricity you pay for versus how much reaches the battery. High frequency chargers typically achieve 90 percent efficiency or better. Older conventional chargers may be only 80 to 85 percent efficient. Lithium ion charging is generally more efficient than lead acid.

Replacement cycles

A lead acid battery lasting 5 years will be replaced multiple times over a 15 year planning horizon. A lithium ion battery lasting 10 to 15 years may never need replacement during the same period. Factor in the cost and disruption of future replacements when comparing options.

Total cost of ownership example

For a 48V forklift running two shifts per day

Cost element	Lead acid (10 year)	Lithium ion (10 year)
Battery purchase	€8,000 × 2 = €16,000	€20,000 × 1 = €20,000
Charger	€2,500	€3,500
Maintenance labour	€6,000	€1,500
Energy (efficiency loss)	€3,000	€1,800
Total	€27,500	€26,800

These figures are illustrative. Actual costs vary by region, electricity prices, labour rates, and specific equipment. The key point is that higher upfront costs can be offset by lower ongoing expenses, particularly in demanding applications.

Safety considerations

Forklift batteries contain large amounts of stored energy and potentially hazardous materials. Safe handling protects workers and equipment.

Lead acid safety

Sulfuric acid causes severe burns. Wear face shields and acid resistant gloves and aprons when working with batteries.
Hydrogen gas is explosive. Ensure ventilation, prohibit smoking and flames, and avoid creating sparks near charging batteries.
Batteries are heavy. Use proper lifting equipment and never attempt to manually lift a forklift battery.
Electrical shorts can cause arcing, burns, and fires. Remove jewellery and use insulated tools when working on battery connections.

Lithium ion safety

Damaged cells can experience thermal runaway. Inspect batteries after impacts and remove from service any pack with visible damage.
Do not expose lithium ion batteries to fire. If a lithium ion battery catches fire, use large amounts of water to cool it and prevent spread.
Follow manufacturer guidelines for storage, charging, and disposal.

General precautions

Train all personnel who handle or charge batteries.
Post safety procedures and emergency contacts in charging areas.
Maintain fire extinguishers and first aid supplies accessible to battery areas.
Report and investigate any battery incidents to prevent recurrence.

Choosing between battery technologies

The right choice depends on your specific situation. Consider these factors

Choose lead acid when

Initial cost is the primary constraint
Single shift operation with overnight charging
Maintenance staff and procedures are already in place
Existing infrastructure supports lead acid charging
Planning horizon is short or uncertain

Choose lithium ion when

Multi shift operation without space for battery swapping
High utilisation demands fast opportunity charging
Reducing maintenance labour is a priority
Cold storage application where battery swapping is impractical
Long planning horizon favours lifecycle cost over purchase price

Consider hydrogen fuel cells when

Very high throughput operation with continuous forklift use
Large fleet size justifies hydrogen infrastructure investment
Fast refuelling is critical to productivity
Corporate sustainability goals favour zero emission technology

Future trends

Battery technology continues to evolve. Trends affecting the forklift industry include

Falling lithium ion costs. Manufacturing scale and technology improvements continue to reduce lithium ion prices, making the business case stronger each year.
Solid state batteries. Next generation batteries using solid electrolytes promise higher energy density and improved safety. Commercial availability for industrial applications is still several years away.
Vehicle to grid integration. Large battery fleets may eventually provide grid services, charging during low demand periods and potentially feeding power back during peaks.
Improved battery management. Advanced BMS software and connectivity enable predictive maintenance, optimised charging, and better fleet management.
Hydrogen infrastructure growth. As hydrogen production and distribution expand for other applications, costs for forklift fuel cell operations may decrease.