For years the workhorse for industrial and commercial material handling of heavy loads has been the forklift with an internal combustion (IC) power plant. Accepted as a necessary evil are the noise, emissions, and performance limitations of conventional forklifts. However, one of the most significant trends in the forklift industry is the increased use of electric-powered forklifts. And, now that an 80 V, 5,000-6,000 lb capacity truck is available, the applications arena for electric forklifts is limitless.

Twenty years ago, the ratio of forklift sales in the U.S. was 55% IC engine-powered and 45% electric-powered; and the electric vehicles were typically used for lighter duty applications. Today, electric forklift sales are approaching 60% of the overall market. The recent growth can be attributed to several factors, including performance and operational improvements, extended range of vehicle capacities, environmental and OSHA concerns, and operating cost benefits.

Performance Enhancements

The general task of all material handling equipment is to move an item from Point A to Point B. The advantage held by IC-powered forklifts is power -- the ability to move heavy loads quickly and efficiently over any terrain. More specifically, they can climb ramps and grades, they can accelerate faster, they reach higher top-end speeds, and they can lift loads faster. Overall, they are regarded as the true workhorse of industry.

Recent advancements in electric forklifts with 48 V and now 80 V ac motors have generated a lot of interest in the market. AC motors offer several advantages, such as high performance, reduced maintenance, and improved energy consumption, to mention a few. However, their load capacity limits have been a drawback. Operators want the freedom (flexibility) to convey all loads with a single truck.

In addition to advances in performance, operators are getting more comfortable with electric forklifts, realizing they are significantly quieter and operate more cleanly. Also, less vibration is transferred from the engine through the seat, floorboard, and steering wheel. Tests have shown reduced vibration keeps operators alert and less fatigued, especially in operations that require extended periods of forklift use.

Advancements In Detail

Several improvements and enhancements have increased the popularity of electric forklifts. The switch to ac drive technology versus dc has provided several operational benefits, as well as environmental advantages. Also, ergonomic controls and digital displays make the vehicles more user friendly.

An ac-powered pallet truck still uses a dc battery. However, an inverter in the truck's controller converts the dc current to 3-phase ac current. AC power is then delivered to the truck's motor, controlling the vehicle's speed and acceleration. The end-user realizes the following benefits:

• Higher Performance -- AC motors allow for quicker speeds up to 12.5 mph, better acceleration and gradeability, and lift speeds up to 108 fpm. Operators notice a faster and smoother response when changing from forward to reverse and vice versa. This improvement in directional changes increases productivity output.
  
• Reduced Maintenance -- Unlike dc motors, ac motors do not have brushes, controller contactors needed for switching the direction of the motor rotation, and motor commutators. Fewer moving parts translates into reduced maintenance costs. In addition, the elimination of brushes means ac motors are much smaller than comparable dc motors.
  
• Improved Energy Consumption -- One of the weak points of electric dc-powered trucks has been the decrease in performance as the battery loses its charge. An ac power system offers the control needed to maintain power even as battery charge runs low -- up to 30% less energy consumption when compared to conventional trucks.

Typical ac systems recover battery energy using three forms of "regenerative" braking: when the accelerator lever is released (coasting), when the brake is applied, and when the directional lever is operated (switch back or plugging). Essentially, the inertia energy that is created by these actions is converted to electrical energy and returned to the battery, extending overall operating times and operating cycles.

Industrial truck manufacturers are constantly searching for ways to meet the pending EPA clean-air regulations. In California, for example, where the California Air Resources Board (CARB) has set standards for emission limits, new trucks take a new approach to emissions. Technical advancements for IC engine trucks, such as 3-way catalytic converters, have been designed to meet the standards. However, electric trucks with their zero-emission capabilities provide the buyer with the ultimate solution to environmental concerns.

Apart from emissions, the elimination of fuel costs can add to acceptance of electric trucks. For example, an electric forklift may cost $4 in electricity, whereas an IC forklift may need $10 in fuel to accomplish the same amount of work. The initial costs of an electric truck with battery and charger may be higher, but the overall true operating costs over time will provide significant savings.

Digital displays on electric vehicles provide operators with instant status information. Speedometer readings, battery discharge gauges, warning messages, and multiple-hour meter readings are common on most trucks. Using built-in analyzers and self-diagnostic capabilities, electrical forklifts with digital displays make troubleshooting quick and easy.

Electric Truck Example

A new line of ac-powered 80 V electric 4-wheel sit-down forklift trucks that provide increased performance and handle loads up to 6,000 lb is now available from Jungheinrich Lift Truck Corp. The vehicles reach travel speeds of 12.4 mph, lift speeds of 108 fpm, and offer a real alternative to combustion trucks, even when using heavy attachments.

The totally enclosed drive axle, which includes motors, gears, and multiple disc brakes is completely maintenance-free. Dust- and moisture-protected axle and enclosed ac controllers, in combination with super-elastic tires, allow the truck to be operated both indoors and outdoors without any compromise.

The new ac controller enables the truck to stop automatically on any gradient when the accelerator pedal is released. For safety reasons, travel speed is automatically reduced when driving around curves. Six-month or 1,000-hour service intervals drastically reduce maintenance cost due to missing contactors and brushes.

Five individually adjustable travel programs are available, from highest performance to energy saving. Also, the ac truck consumes up to 30% less energy than conventional electric forklifts.

To learn more about AC Travel Drive Trucks, contact Jungheinrich Lift Truck Corp using the contact information below.

The power source of an electric forklift is an industrial battery. Industrial batteries, like IC engines, require attention. For example, proper water, electrolyte, and charge levels must be maintained. Batteries must be allowed to cool after receiving a full charge, and surface corrosion should be minimized.

Since the advent of video recorders, cellular phones, and laptop computers, the general public has become more "battery-knowledgeable" than ever before. A more educated customer base has lowered the intimidation factor that sometimes prevailed regarding the purchase of an electric forklift. Over the years, end-users have realized that proper battery care is critical to overall forklift performance and lowers the cost of ownership for a forklift and its battery.

Technical advances in industrial batteries are also resulting in increased customer acceptance. Single-point watering systems; sealed batteries that require no watering; automatic "smart" chargers; opportunity charging; and fast-charge technology are all available features that should be discussed with forklift and battery representatives to determine application compatibility.

Battery-changing devices also should be studied carefully if the end-user operates each truck longer than one shift or needs more than one battery per vehicle. For removal and installation, overhead cranes are commonly used to lift the battery out of the forklift. However, side-removal equipment, which allows the operator to pull the battery out of the forklift and onto a platform, is becoming more popular. Forklift designers have recognized this trend, and most electric forklifts now have features that allow for side removal.