The Development Status and Performance Advantages of Lithium Battery Forklifts

Since Sony released the world’s first commercial lithium battery in 1991, lithium batteries have been developing at a rapid rate for more than 20 years and have been widely used in various fields. In the field of industrial vehicles, relying on its own advantages in the field of lithium iron phosphate batteries, BYD launched the first domestic electric forklift equipped with lithium batteries in 2013, heralding the arrival of a new era. With the introduction of national environmental protection policies and the continuous improvement of people’s awareness of environmental protection, electric forklifts have gradually gained the favor of users, and market sales have continued to grow steadily. Among them, the growth rate of lithium battery forklifts is even more outstanding. Forklifts are widely used in ports, docks, factories, airports and other places, which can greatly improve the efficiency of short-distance transportation and cargo handling in specific places; moreover, with the rapid development of modern logistics and warehousing, its application scenarios continue to expand and the number of demand continues to increase.

Forklifts are industrial handling vehicles, which refer to various wheeled handling vehicles for loading, unloading, stacking and short-distance transportation of finished pallet cargo. Forklifts need to operate in small spaces. For this type of forklift, for the flexibility of operation and the requirements for working space, the volume of the forklift needs to be reduced as much as possible. However, the reduction in the size of the forklift will cause the driver’s operating space to be reduced, which affects the operator’s operating comfort.

In addition, the small size of the forklift is relatively compact due to the limitations of the design space. This is also quite inconvenient for forklift inspection, repair and maintenance. Existing battery-powered forklifts generally use lead-acid batteries. However, due to the relatively large size of lead-acid batteries, the batteries are generally set close to the cockpit of the forklift, that is, under the driver’s seat. As a result, on the one hand, the space occupied by the lead-acid battery is too large, resulting in a larger forklift; on the other hand, the replacement of the forklift battery requires the help of a crane, which is very inconvenient.

On the other hand, electric forklifts in the prior art generally focus on mechanical steering, relying on the hydraulic power steering of the main oil circuit, and the steering mechanism is connected by a universal wheel under the steering wheel. This is currently the most widely used hydraulic steering connection design. Turning the steering wheel finally drives the steering gear to rotate, and the power is directly provided by the mechanical-hydraulic-mechanical method. Such a steering method must rely on the power of the pump motor, so that the pump motor is working non-stop all the time, which is also very wasteful in energy consumption, and the torque of turning the steering wheel by hand is also quite large, which is quite tiring for workers who operate for a long time. The other is to increase the electronic power steering of the steering motor separately. However, the former consumes too much energy and has poor operability. Due to the limitations of the mechanical structure, most of the latter are currently only used in single-drive three-point forklifts.

In order to solve above problems, the researchers involuntarily set their sights on lithium batteries. Lithium batteries have the functions of fast charging, full load, high current discharge, and high current charging. After being equipped with lithium batteries, the forklift operation efficiency is higher. The manufacture of lithium batteries has the characteristics of high precision, high speed and high intelligence, which ensures that the batteries in the lithium battery pack have high consistency. There is an overcharging phenomenon in the charging of lead-acid batteries, which is prone to vulcanization, which greatly shortens the service life of lead-acid batteries. The lithium battery power management system (BMS) can monitor and manage the charge and discharge of the battery, which is conducive to extending the service life of the lithium battery. In short, the use of lithium batteries can make the layout of the various components of the forklift reasonable, and the volume of the forklift can be effectively reduced.

As the only source of power for electric forklifts, the power battery directly determines the power performance and economic performance of the forklift. With the gradual improvement of the national new energy subsidy policy, various power battery manufacturers urgently need to produce power battery packs with high specific energy, long life, good magnification and high reliability; among them, the level of specific energy has a profound impact on the range of electric forklifts and the market application prospects. At present, the first commercial application in the market and the most widely used is lead-acid batteries. Its main advantages are low price and stable performance; however, the disadvantages are also more obvious, the size is larger, the specific energy is low, and the more serious is that the lead-acid liquid used is harmful to the environment and the recycling cost is high; the wide-scale use of power batteries requires higher battery life to meet actual needs, which all determine that lead-acid batteries are not suitable for the present and will inevitably be replaced by new power batteries; In this context, lithium-ion batteries have gradually shown huge advantages.

Lithium-ion batteries have a series of advantages such as high monomer voltage, large specific energy, long cycle life, small self-discharge, support for fast charging, and no memory effect. Of course, the price is also the highest compared to other types of batteries. However, due to the characteristics and production technology of lithium-ion batteries, lithium-ion batteries have obvious nonlinear, inconsistent and time-varying characteristics, and even the performance of the same batch of batteries is not the same. Long-term use, due to the different charging acceptance capacity, self-discharge and capacity attenuation of the battery, will further lead to differences between groups of batteries, resulting in the potential for overcharging and over-discharging of the monomer. If effective measures are not taken to deal with this situation, it will seriously affect the power performance of the entire battery pack, and in severe cases, it may cause serious consequences that threaten personal safety. Therefore, in order to ensure the safety and reliability of the power battery pack, a special battery management system must be used to monitor and guarantee its operation in real time, which is essential to maintain the high performance of the battery pack and extend its service life.

The current application of lithium-ion batteries has been relatively extensive, but it is far from a mature stage. There are many problems. For example, most of them now use the cycle life of a single battery to represent the use of the entire battery pack. Judging from the existing experimental facts, when dozens or hundreds of single batteries are used in series, their overall life is much lower than the cycle life of the single battery. The price of power batteries generally accounts for 30% to 50% of the total price of electric forklifts, and its role in the development of electric forklifts is self-evident; however, in the actual use of electric forklifts, there are more factors that may damage the battery itself, such as excessive temperature, overcharge, over discharge, etc. Therefore, the battery management system must be indispensable to enhance the safety of electric forklifts and improve energy utilization.