Below is a calculator to help you determine the best motive energy source for a fleet of forklifts. Then read on for a comparison of three motive energy power sources for forklifts, including the advantages and disadvantages of each power source.
Best Motive Power Energy Source for Forklifts
In this comparison of three motive energy power sources for forklifts, we will look at lead-acid batteries, lithium-ion batteries, and hydrogen fuel cells.
History of Lead-Acid Batteries and Charging Strategies
The lead–acid battery is a type of rechargeable battery first invented in 1859 by French physicist Gaston Planté. It is the first type of rechargeable battery ever created. Compared to modern rechargeable batteries, lead–acid batteries have relatively low energy density. Despite this, their ability to supply high surge currents means that the cells have a relatively large power-to-weight ratio. These features, along with their low cost, make them attractive for use in motor vehicles, such as cars and ICE forklifts, to provide the high current required by starter motors. Lead-acid batteries in electric forklifts suffer from a relatively short overall lifespan, usually less than 1500 cycles, due to the sulfation in the discharged state.
Nevertheless, the combination of weight and energy density made lead-acid batteries the standard for powering electric forklifts over an 8-hour shift.
Charging strategies for forklifts
Traditional charging cycles were designed around 8 hours to power the forklift (discharge), 8 hours to recharge, and 8 hours to cool.
Standard chargers are matched to the battery based on voltage and total amperage. They charge at the rate of 12% of the stated ampere hour capacity of the battery for the first 6 hours, and then they taper their charging rate to 3% in the last 2 hours to finish and gas the battery. The finishing charge tops the battery up to ~100% and the gassing phase mixes the electrolyte consistently, top to bottom, in the battery. Gassing creates the need for regular watering of the battery.
Overwatering causes boilovers, a dilution of electrolyte, the need for regular acid adjustments, and a mess to clean up on the floor. Spill kits are a required feature for every battery room.
Although lead-acid batteries have changed little over time, charging has changed significantly over the last 30 years.
The advent of opportunity charging for forklifts
Opportunity charging is a popular strategy to extend a standard shift from 8-10 hours by charging on breaks.
In 2005, opportunity chargers started to become popular despite initial market resistance. The high-powered chargers shortened the main charging time from 6 hours to 4 hours. This was achieved by raising the charging rate to 25% of the stated ampere hour capacity of the battery. Chargers, however, taper their charge rate based on the charging resistance of the cells by polling for both voltage and heat through a thermistor installed in the center of the battery. By regulating charging when the batteries are hot, the smart charger can extend the otherwise shortened life of the battery. Despite this, opportunity-charged batteries are not expected to last much longer than 3 years.
Strict adherence to an opportunity charging schedule during statutory breaks is a must. Failure to place the forklift batteries on charge during breaks will risk the lift truck running out of energy before the end of the shift. If the battery is too hot to charge over the break, the battery may run out of current, and force the lift truck and its operator to be idle during the remainder of the shift.
Fast charging for forklifts
To extend the shift life of batteries for longer than 10 hours, fast charging was introduced.
Although fast charging has been around since the 1970s, fast-charging forklifts involves charging 80% of a battery at 40% to 50% of the stated ampere hour capacity of a forklift battery. This reduces the charging time from 6 hours to 2 hours. Great care, however, must be taken when charging the batteries at this rate, as heat severely impacts the lifespan of the battery, reducing its life to only a couple of years. Additionally, fast charging is never recommended for more than 2 shifts. This is because a battery must have time to cool, must have a full 8 hours to charge fully, and must have the opportunity to equalize charge for a full 12 hours on a weekly basis at a minimum.
Lead-Acid Batteries for Forklifts Advantages
- Good (but not great) energy density: Lead-acid batteries can store a large amount of energy in a relatively small space. They have good power to weight ratio, which makes them well-suited for forklift operations.
- Long lifespan: With proper maintenance, lead-acid batteries can last for over seven years.
- Wide availability: Lead-acid batteries are widely available and easy to find, which makes them a convenient choice for forklift fleet managers. The technology is widely accepted and familiar to most forklift drivers and operations managers.
- Recyclable: Lead-acid batteries are 98% recyclable, with lead recycling facilities available in most major population centers.
- Lead-acid batteries are heavy, which is useful for material handling equipment by providing ballast weight for the forklift.
Disadvantages of Lead-Acid Batteries for Forklifts
However, lead-acid batteries also have some weaknesses, including:
- Heavy weight: Lead-acid batteries are relatively heavy, which can make them difficult to handle, and slow to exchange in a multi-shift operation. Whereas the weight is an advantage for forklift ballast, there is a downside to extracting, exchanging, and moving lead-acid batteries around. Their handling is difficult and dangerous, requiring specialized equipment and significant time.
- Short lifespan: Lead-acid batteries can be expected to last a long time when watered, washed, acid-adjusted, charged slowly, and allowed to cool properly. You can expect a much shorter lifespan for lead-acid batteries when they are opportunity-charged, fast-charged, over discharged, poorly maintained, not watered regularly, and allowed to overheat, and allowed to boil over during charging.
- Maintenance required: Lead-acid batteries require regular maintenance, including frequent watering, acid-adjustment, and cleaning.
- Environmental concerns: Lead-acid batteries are not environmentally friendly, as they contain lead and sulfuric acid, both of which can be harmful to the environment if not disposed of properly.
- Sensitive to extreme temperatures: Very cold and very hot environments will reduce the shift life of lead-acid batteries significantly. In cold-storage environments, lead-acid batteries will lose up to 50% of their rated capacity due to cold temperatures. Never store a lead-acid battery in the cold. A frozen battery will damage the internal cells and will not work properly.
- Safety concerns: Lead-acid batteries contain sulphuric acid which can poison the air with acid if allowed to charge dry, can splash acid on maintenance workers, require PPE when handling, and are very heavy which creates a danger when handling. Spill kits are a required safety item, and are used for when a battery tips over. Every precaution should be taken to prevent the battery from spilling its electrolyte into drains, sewers, and streams.
- Lead-acid batteries require equalization charging – 12-hour charge. Lead-acid batteries contain cells that charge and discharge at different rates. Equalization charges are needed to bring all the battery cells up to full charge using a prolonged slow trickle charge. 7-day per week operations that do not have enough time to equalize-charge their batteries will find the batteries have a much shorter shift-life and operating lifespan, increasing the need for early replacement.
- Batteries are not GHG zero-emission – Lead-acid batteries are most often refueled with high-carbon intensity electricity (61% of grid energy is produced using fossil fuels in the United States).
Overall, Lead-acid batteries are a reliable and cost-effective option for forklifts, but they do have some significant limitations.
Recommendation: Lead-acid batteries make sense for single shift operations. A shift and a half operation is possible when using opportunity chargers. A battery exchanger is required for multi-shift operations.
History of Lithium-Ion Batteries for Forklifts
Research on rechargeable Li-ion batteries dates to the 1960s; one of the earliest examples is a battery developed by NASA in 1965.
Exxon tried to commercialize a lithium battery in the late 1970s but found the synthesis expensive and complex, and sensitive to moisture. The early chemistry released toxic gas on contact with water.
In 1987, Akira Yoshino patented what would become the first commercial lithium-ion battery. In 1991, using Yoshino’s design, Sony began producing and selling the world’s first rechargeable lithium-ion batteries.
Significant improvements in energy density were achieved in the 1990s.
In 2019 the Nobel Prize in Chemistry was awarded to the early scientists “for the development of lithium-ion batteries”.
Guidelines for storing lithium-ion batteries for forklifts
Although the design of Lithium-ion batteries has evolved over the years, manufacturers have some strict guidelines around storing lithium-ion batteries in either a fully charged or a fully discharged state. Storing a battery fully charged will reduce the battery’s life span. Storing it in a fully discharged state can cause the lithium-ion battery to combust. To avoid these dangers, it’s best to store lithium-ion batteries at a charge level between 40-60%. If you’re storing a lithium-ion battery for an extended period of time, it’s also a good idea to charge and discharge it once every few months to help maintain its health.
Lithium-ion batteries will lose 20% of their cyclable charge capability irreversibly over 3-5 years, or after 1000-2000 cycles at 25C. That means lithium-ion batteries are best on their first day of use, but degrade over time and/or use.
The problem of heat with lithium-ion batteries for lift trucks
Batteries generate heat when being charged or discharged, especially at high currents. Large battery packs, such as those used in electric vehicles and forklifts, are generally equipped with thermal management systems that maintain a temperature between 15 °C (59 °F) and 35 °C (95 °F). Poor internal ventilation may increase temperatures. For large batteries consisting of multiple cells, non-uniform temperatures can cause accelerated degradation.
Because lithium is only able to cool itself through heat radiation, heat concentrations can be a challenge both to the operation of the battery and the durability of heat-sensitive components in the lift truck. Said another way, the battery will create reliability challenges and component failures in the lift truck. This is not something you want if your goal is to operate a reliable fleet of material handling equipment.
Advantages of Lithium-ion Batteries for Forklifts
Lithium-ion batteries are becoming increasingly popular in forklifts due to their high energy density and long lifespan. Their strengths include:
- Batteries are sealed: Lithium-ion batteries will not leak acid if tipped over. This means you can orient batteries on their sides without fear of leaks or spills.
- High energy density: Lithium-ion batteries can store a large amount of energy in a relatively small space, which allows for longer run-times if the battery ampere hour rating is sized appropriately.
- Quick to recharge: Lithium-ion batteries, when using a high-capacity charger can be fully recharged in one hour only.
- Long lifespan: With proper maintenance, lithium-ion batteries can last for several years, much longer than lead-acid batteries. Early estimates have suggested a 13 year lifespan, although in practice, the operating life is proving to be shorter.
- Low maintenance: Lithium-ion batteries require less maintenance than lead-acid batteries. Lithium-ion batteries for forklifts do not require regular watering or annual cleaning.
Disadvantages of Lithium-ion Batteries for Forklifts
Lithium-ion batteries are not without their disadvantages.
- Expensive: Lithium-ion batteries are more expensive than lead-acid batteries. Expect to pay 2.5 times the cost of a lead-acid battery. Due to their relatively high cost, lithium-ion batteries are usually manufactured to contain 66% of the rated AH capacity as their lead-acid batteries they are replacing. As a result the require frequent recharging.
- High-temperature sensitivity: Lithium-ion can perform well at elevated temperatures but prolonged exposure to heat reduces longevity. Charging and discharging at elevated temperatures is subject to gas generation that might cause a cylindrical cell to vent and a pouch cell to swell. Many chargers prohibit charging above 50°C (122°F).
- Low-temperature sensitivity: In general, lithium-ion batteries can be discharged in temperatures as low as -4°F (-15°C), but their energy density and capacity can be decreased at extremely low temperatures. At very low temperatures, the ions move slower through the electrolytes, resulting in a reduction of capacity. Additionally, low temperatures cause the charge transfer velocity to decrease, which can make it difficult to charge a battery. The lowest charging temperature of a lithium-ion battery is 32°F (0°C). If a battery is charged in freezing temperatures, it can cause permanent solid electrolyte interphase (SEI) buildup on the anode, creating irreversible damage to the battery.
- Reduced shift-life in cold temperatures: Expect lithium-ion batteries to provide up to 35% less energy when operating in cold temperatures.
- Safety concerns: Lithium-ion batteries have the potential to catch fire if they are damaged or stored for long periods in a discharged state, or overcharged, which can be a safety risk. Lithium-ion battery fires are extremely difficult to extinguish.
- Maintenance can be expensive: Some forklift lithium-ion battery manufacturers recommend rewiring lithium-ion batteries once or twice a year at the cost of $600 per service. This is required to reduce the premature wear and tear in the cell closest to the charger cable. They call this practice, “shuffling the deck”.
- Charging concerns: To take advantage of lithium-ion batteries’ quick recharge capabilities, an expensive high-capacity charger is required. The charger can pull significant amps from the wall and increase peak-demand charges on one’s electricity bill. The current demand in any 15 minutes in any 24-hour period will be considered the day’s demand and a company will be charged at that peak rate for the entire day. This is how a 14 cent/kwh rate can be billed at 32 cents per kWh.
- Recycling concerns: Lithium-ion batteries cannot easily be recycled and very few recycling facilities exist for lithium-ion batteries. In some instances, one lithium-ion forklift battery can cost up to $2,000 in disposal fees. Lithium-ion battery manufacturers promise to take used and failing batteries back on trade and reuse them for other applications. Be sure to receive this commitment in writing.
- Storage concerns: Lithium-ion batteries stored in a discharged state can become volatile and catch on fire. Always store lithium-ion batteries at 40%-60% state of charge. Damaged or unstable batteries and improper charging, storage or disposal can cause the batteries to overheat, leading to an explosive, aggressive fire that spreads rapidly, can reignite and is challenging to extinguish. Lithium-ion battery fires are very dangerous. Water may not prevent a battery from burning and spreading. Battery cells are known to explode and quickly spread to another battery. Lithium-ion fires can spread to other devices. These batteries may continue to generate heat even when there is no visible sign of fire. Once heat reaches a certain level fire may reignite in the battery and surrounding area. Fire Extinguishers do not work on lithium-ion battery fires. If you observe a lithium-ion battery fire, leave the area, CLOSE the door, and call 911 immediately. Reignition of lithium-ion batteries is common. Lithium-Ion batteries are known to unexpectedly re-ignite (without warning) minutes, hours and even days after all visible fire has been put out. Lithium-ion batteries can enter an uncontrollable, self-heating state. This can result in the release of gas, cause fire and possible explosion.
FDNY will take immediate action if hazardous conditions are discovered
In summary, Lithium-ion batteries are a good option for small fleets of forklifts because they have a longer life-span, less maintenance, and are quick to recharge. But due to the expense of charging, the high current demands, heat issues, and the acquisition expense, they are not the perfect solution for all fleets and all operations.
History of Fuel Cells for Forklifts
Fuel cells have been used in forklifts for several decades now, and their use in this application has steadily increased over time. The history of fuel cells for forklifts dates back to the early 1990s, when the first fuel cell-powered forklift was developed by General Motors (GM) and presented at the 1992 World’s Fair in Seville, Spain.
Fuel cells were first invented in 1839 by Sir William Grove, a Welsh judge and physicist. However, it wasn’t until the 20th century that scientists and engineers began to seriously explore the potential of fuel cells as a source of clean, efficient, and reliable energy. In the 1960s and 1970s, fuel cells were developed for use in NASA’s space program, and since then, they have been the subject of ongoing research and development efforts, with the goal of making them more practical and affordable for widespread use in a variety of applications, including transportation, stationary power generation, and portable power.
How hydrogen fuel cells work
Fuel cells work by converting the chemical energy from hydrogen into electricity, which can then be used to power a vehicle or machine. In the case of forklifts, the fuel cell generates electricity to power the electric motor, which drives the wheels and performs the lifting and carrying operations.
One of the main benefits of using fuel cells in forklifts is that they provide a much longer operating time compared to traditional battery-powered forklifts. With battery-powered forklifts, the batteries need to be recharged periodically, which can take several hours and can cause downtime in the warehouse. In contrast, fuel cells can be refueled in a matter of minutes, allowing for continuous operation of the forklift.
Environmental benefits for hydrogen fuel cells in forklifts
Fuel cell-powered forklifts also offer significant environmental benefits, as they do not emit any harmful pollutants during operation. This makes them an attractive option for companies looking to reduce their carbon footprint and meet sustainability goals.
In 1997, GM launched the first commercial fuel cell-powered forklift, which was designed to operate in a warehouse environment. The fuel cell-powered forklift had several advantages over traditional battery-powered forklifts, including faster refueling times, longer operating times, and better overall performance.
Fuel cell leaders in the material handling equipment industry
Over the years, other companies such as Toyota, Hyster-Yale, and Plug Power have also entered the fuel cell forklift market, offering a range of products and solutions for various industries.
Plug Power is a company that was founded in 1997 and is based in Latham, New York. It is a leading provider of hydrogen fuel cell systems for material handling equipment, such as forklifts, and is also involved in the development of hydrogen fueling infrastructure.
The company was initially focused on developing proton exchange membrane (PEM) fuel cell systems for the telecommunications industry, but later shifted its focus to material handling equipment in the early 2000s. In the following years, Plug Power made several strategic acquisitions and partnerships, allowing it to expand its capabilities and build a strong position in the hydrogen fuel cell market for material handling equipment.
In recent years, Plug Power has been at the forefront of efforts to commercialize hydrogen fuel cells for use in a wider range of applications, including heavy-duty vehicles and data centers. The company has established commercial partnerships with major retailers, such as Amazon and Walmart, to bring forklift fuel cell solutions to their operations. It has also been involved in the development of hydrogen fueling infrastructure, with the goal of making hydrogen fuel more widely available for use in transportation and other applications.
In summary, the history of fuel cells for forklifts dates back several decades and has seen significant advancements in technology and adoption. Fuel cell-powered forklifts offer numerous advantages over traditional battery-powered forklifts, including longer operating times, faster refueling, and better overall performance. As companies continue to prioritize sustainability and environmental responsibility, it is likely that the use of fuel cell-powered forklifts will continue to increase in the future.
Fuel Cells for Forklifts Advantages
Fuel-cell powered forklifts are becoming increasingly popular due to their quick refueling capabilities and long shiftlife operation. Their strengths include:
- High energy density: Fuel cells can store a large amount of energy in a relatively small space, which allows for longer run-time and fewer battery changes. 10-hour shifts on a single refueling have been reported.
- High efficiency: Fuel cells are highly efficient and can convert 50% to 60% of the energy stored in the fuel into usable electricity (depending on size and operating load).
- Low emissions: Fuel cells produce zero emissions, making them an environmentally friendly option. When operating, they produce only electricity, water, and heat. No greenhouse gasses are produced in the production of electricity.
- Quiet operation: Fuel cells are quiet in operation compared to internal combustion engines. All the benefits of fossil fuel without the noise.
- Quick to refuel: Fuel cells for forklifts can be fully refueled in under 3 minutes, with a shift lasting up to 10-hours, depending on the workload.
- One fuel cell per forklift: fuel cells stay in the forklift and are refueled, as necessary. The only time you remove them is for maintenance and repair. That means you do not need to exchange the forklift’s powersource, nor do you need to wait while the forklift’s powersource is being recharged.
- The labor savings: no exchange and short refueling. Not having to remove the fuel cell for refueling is significant and can represent a major savings for warehouse distribution operations.
- No voltage droop: Fuel cells deliver a steady high voltage which reduces maintenance costs and increases productivity, especially with pallet lifting speeds.
- 30% ITC tax credit: The Investment Tax Credit (ITC) is a federal tax credit that incentivizes businesses and individuals to invest in certain qualified assets, such as renewable energy systems or energy-efficient equipment. The ITC allows taxpayers to reduce the amount of federal income tax they owe by the value of the credit, which is calculated as a percentage of the cost of the qualifying assets. The specifics of the ITC program depend on the type of asset being invested in, as well as the year in which the investment was made. However, some general features of the ITC include:
- Eligible assets: The types of assets eligible for the ITC can vary, but typically include solar, wind, fuel cell, geothermal, and microturbine systems. Some energy-efficient equipment, such as HVAC systems, lighting, and building insulation, may also be eligible.
- Credit amount: The amount of the ITC depends on the type of asset being invested in but can range from 10% to 30% of the cost of the asset. The exact credit amount can change from year to year, so it is important to check the most up-to-date information.
- Timing: The ITC is claimed in the year that the investment is made and can be used to offset the taxpayer’s federal income tax liability for that year. If the credit is more than the taxpayer’s tax liability for the year, the excess can be carried forward to offset tax liability in future years.
- Recapture: If the taxpayer disposes of the asset within a certain timeframe (usually five years), they may be required to “recapture” a portion of the credit by paying back the government.
Overall, the Investment Tax Credit is a valuable tool for businesses and individuals looking to invest in certain types of renewable energy or energy-efficient assets like Plug Power GenDrives. By reducing the cost of these investments, the ITC helps to encourage the growth of these industries and more importantly, the adoption of clean energy technologies.
Fuel Cells for Forklifts Disadvantages
However, fuel cells are not for everyone:
- High cost: Fuel cells are not cheap and can be more expensive than traditional power sources, such as lead-acid batteries, which can make them a less cost-effective option for some forklift operators. They do however compare favorably with lithium-ion batteries. Fuel cells can cost two to two and half times more than a lead-acid battery, which is why they are recommended for multi-shift applications.
- Skilled maintenance required: Fuel cells are more complex than traditional power sources and require specialized training to repair. Maintenance, however, is fairly simple, involving filter changes and checking coolant. Repairs are more complicated.
Need hydrogen storage infrastructure: Just like any energy system, the warehouse or distribution center requires a way to deliver the energy into the building. Instead of additional electrical supply, green H2 storage and dispensing is provided. This hydrogen infrastructure is often less expensive than upgrading the electrical infrastructure.
Fuel cells are not inherently “better” or “worse” than batteries. Both fuel cells and batteries are energy storage devices, and each has its own strengths and weaknesses.
Batteries store energy in the form of chemicals and release that energy through an electrochemical reaction. Batteries are well-suited for applications that require a compact, portable source of energy, such as cell phones and laptops.
For batteries to work, you will need SPACE, TIME, and ELECTRICAL CURRENT. When these are present in abundance, batteries are a great choice. When they are not, fuel cells are a compelling alternative.
Fuel cells generate electricity through a chemical reaction between hydrogen and oxygen, producing water as the only byproduct. Fuel cells are typically larger and more complex than batteries but can provide a continuous source of electricity for much longer periods of time, making them well-suited for applications that require a reliable, long-lasting source of power, such as electric vehicles, forklifts, or backup power systems.
In terms of efficiency, fuel cells are typically more efficient at converting chemical energy into electrical energy than batteries, as the reaction in a fuel cell is continuous as long as hydrogen is supplied, while the reaction in a battery is limited by the amount of stored energy.
Ultimately, the choice between a fuel cell and a battery will depend on the specific application and the user’s requirements. Each has its strengths and weaknesses, and each is best suited for different types of applications.