INTERESTING FACTS ABOUT ELECTRIC FORKLIFTS

As far as powered industrial trucks are concerned, the forklift truck in all its forms is one of the most important game changers in the global economy. Electrically powered models came onto the market quite early on, but remained fairly niche products for a long time. Today, however, electric forklift trucks of this type have no alternative in some areas and are increasingly competing with conventionally powered models in other segments. But what makes these special forklifts so special?

This is usually an electric motor drive. It comprises the following components:

• Accumulator: It acts as a storage unit for electrical energy and must be charged regularly by an external power supply.
• Electric motor: It converts the electric current into a rotary motion. This is used in two ways:
• Hydraulic pump: It pressurizes hydraulic fluid. This pressure is used in particular to control the entire lifting system.
• Differential gearbox: This is also directly connected to the electric motor and distributes its rotary motion to the driven wheels of the electric forklift truck.

Some models take a slightly different approach. They have two electric motors, each of which acts on one wheel. This eliminates the need for a differential gear. It is also possible to have both motors turn in different directions with the appropriate control elements. Such electric forklifts can turn on the spot, similar to a bulldozer, for example. This now applies to both two- and four-wheeled forklifts.

The rest of the technology, on the other hand, is largely uniform. Likewise, the operating concepts hardly differ from one another. This means that anyone who can operate an IC engine-powered forklift truck will not need a major rethink to be able to safely control a similarly sized electric counterpart.

Late developer of industrial trucks

The forklift truck as a self-propelled vehicle with two forks for standardized pallets, as we define it today, is the end result of a long development process. This began in Great Britain and the USA during the First World War (1914-1918).

Towards the end of the 1930s, the forklift truck had become an indispensable logistical aid, particularly in the USA. Electric drives were already in use. For example, the manufacturer Yale & Towne had already developed an electrically powered forklift truck in the early 1920s.

However, the majority of forklifts of that era were powered by internal combustion engines. Electricity, if used at all, was primarily used to lift the forks, although hydraulics also played a major role here. The electric forklift truck therefore remained an absolute niche product. Not least because technical developments at the time did not allow for compact batteries with a high power density.

 

The Second World War saw the forklift truck literally triumph. In the USA in particular, neither the gigantic production volumes nor the huge logistical supply around the globe would have been possible without so many forklift trucks and standardized pallets.

In the first decades after the war, the forklift truck became an increasingly important helper between production and logistics in many other nations following this impressive demonstration of its capabilities. But then two things happened:

1. Oil became more and more expensive, which finally culminated in the first oil crisis in 1973.
2. The topics of occupational health and safety and environmental protection were given a much higher priority.

Neither of these meant the end of petrol and diesel-powered forklifts. Nevertheless, a rethinking process was initiated.

In 1971, for example, Linde launched its first electric forklift truck, the E10-E15. The model quickly proved to be a success. In the years that followed, more and more other manufacturers also brought electric forklift trucks onto the market.

In the meantime, the electric forklift truck has not only established itself globally, but has also become the only forklift truck in use in various sectors – not least due to legal requirements in many countries.

LOW EMISSIONS AS A STRONG – BUT NOT THE ONLY – ARGUMENT

Since the electric drive in forklift trucks went from being a marginal product to an established form of drive, practically nothing has changed in terms of its strengths:

Exhaust gas free

Since no form of combustion takes place in an electric motor, an electric forklift truck operates completely emission-free. Even when the first models appeared, this meant an enormous reduction in the workload for operators and other people on site, especially in warehouses and other indoor areas.

Because where air exchange is only possible by technical means due to the conversion, even intensive use of electric forklift trucks does not affect the air quality.

As a result, electric forklift trucks are the only type of industrial truck in Germany that can be used indoors without any restrictions – regardless of how well or poorly the rooms are ventilated. Even gas-powered forklift trucks, which have lower exhaust emissions (compared to diesel-powered forklift trucks), may only be used indoors under strict ventilation conditions.

Low noise

No combustion, no air intake, no exhaust pipe. These three technical realities of an electric forklift truck ensure very low operating noise. In practice, this is limited to a rather high-pitched hum that only gets louder when the hydraulic pump has to work. Once again, this is a great relief for forklift drivers and anyone else working in the immediate vicinity.

As the low volume does not impair human communication and hearing in particular, it also contributes to safer operation overall.

 

Technical simplicity

Electric forklift trucks may be powerful industrial trucks. However, when it comes to drive technology, they have a very simple design. The electric drive has few moving parts. It also requires no cooling, no extensive lubrication (including the necessary auxiliary units) and only a differential gear.

This provides several advantages: The drive is more compact overall. The probability of failure is reduced because fewer parts are installed overall and the electric motor has fewer moving parts. For the same reason, maintenance and inspections can be carried out more quickly and cost-effectively – similar to repairs for drive-related damage.

Security

The electric forklift truck has another strength, especially for use in areas where there is a risk of fire or explosion: Explosion protection through encapsulation is much easier to apply here than with all other types of drive due to the drive concept.

Almost all electric forklifts are more expensive to purchase than comparable diesel or gas-powered forklifts. However, this initial cost disadvantage is offset by the lower running costs. This applies not only to maintenance and repairs, but also to energy supply in particular.

Electric forklift trucks, performance classes and areas of application

Today’s electric forklift trucks are hardly less versatile than the combustion engine-powered version. Nevertheless, with a few exceptions, it has so far tended to be a machine for handling light to medium-duty tasks. Most of these vehicles are designed for use on firm, level surfaces – although the first all-terrain electric forklift trucks have recently been launched on the market.

 

Most of today’s electric forklifts are designed for either pure indoor or mixed operation. As with other forklifts, the performance classes differ depending on the maximum lifting load. In contrast to this, however, in the case of electric forklifts this is always linked to the voltage of the battery and electric motor. The (rough) subdivision is as follows:

• Light electric forklifts: 12 to 24 volts; 0.5 to 1.5 tons
• Medium electric forklifts: 36 to 48 volts; 1.5 to 2.5 tons
• Medium-duty electric forklifts: 80 volts; 5.0 to 8.0 tons

However, it should be noted that these are only common, approximate figures. Recently, there have been various electric forklift trucks that push the performance limit upwards. For example, the manufacturer Kalmar has an electric forklift truck in the 9.0 to 18.0 ton class in its repertoire. Competitor Hyster also offers a model that can lift between 10.0 and 18.0 tons.

These types of forklift trucks are now possible, mainly due to further developments in battery technology and drive control. As a result, more energy can be stored in the same amount of space, while consumption is reduced to a minimum thanks to digital control.

THE BATTERY: POWERFUL ENERGY STORAGE WITH A DUAL FUNCTION

How long does a forklift truck have to “last”? The answer to this question is primarily determined by how frequently and intensively it is used during a shift. In this respect, all electric forklifts have a certain disadvantage: compared to diesel and gas-powered forklifts, their battery requires a significantly longer period of time to be fully charged again.

This is by no means a problem in every scenario in which electric forklift trucks are used. In many companies, the vehicles are used in such a way that they can always be connected to a power source in the meantime. When the electric forklift truck is then needed, its battery is always sufficiently charged.

Where, on the other hand, an ideally more permanent use is desired, two battery technology solutions exist today:

• More battery capacity: A simply larger battery and/or a chemically different structure allows more energy to be stored per vehicle. This extends the service life between two charges, in some cases considerably.
• Interchangeable systems: The entire battery is designed as an encapsulated component. It is connected to the electric forklift truck via a rail system and quick connectors for the electrical system. With the help of another industrial truck, the empty battery can be removed in its entirety and replaced with a fully charged element – a job that only takes a few minutes.

The latter in particular is currently a very busy field of development in its own right. Various companies, including the forklift truck manufacturers themselves, have designed several swap systems and are vying for customer favor. The aim is to make battery swapping even easier and faster.

 

But what technology do electric forklift trucks use to store the necessary electricity? Only one thing is standardized here: direct current is always stored in the battery. Depending on the forklift truck, this is then either used in a DC motor or first passed through an inverter and from there to a three-phase motor. The latter is particularly impressive due to its greater torque even at low speeds and even lower maintenance requirements.

Two key battery technologies

As far as the battery itself is concerned, two main technologies still exist in parallel:

• Lead-acid batteries: They are the oldest power storage technology and are still the cheapest solution. In addition, the comparatively high weight has the advantage that an additional counterweight is not required for many electric forklift models. The disadvantages are a certain amount of maintenance, the lower capacity and a memory effect. Incorrect charging can therefore greatly reduce the capacity – at least if the forklift truck does not have an adapted battery management system. Electric forklift trucks with these batteries are widely used in companies with single-shift operations and other businesses with more sporadic forklift truck use.
• Lithium-ion batteries: These batteries are more powerful in every respect: they can store more energy and therefore last longer. At the same time, they require less charging time. Their weight is only around 30 percent of a lead-acid battery with the same capacity. This makes the use of interchangeable systems easier. In addition, there is no real memory effect due to their design. However, all this literally comes at a price: electric forklifts with lithium-ion batteries are more expensive to purchase. Due to their advantages, however, they are likely to become the predominant technology in the medium to long term.

At present, the only way to find out which system is better suited to a company is to make a comprehensive calculation. Roughly speaking, the more intensively and frequently a forklift truck is used, the more likely it is that the additional expenditure for a lithium-ion battery will pay off.

 

Picture credits:

Image 1: Adobe Stock © romaset

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