Equipment Buying Guide: Battery basics

Having the right battery and battery maintenance program for the job are key to getting the most from your battery-powered lift truck or automatic guided vehicle.

By Bob Trebilcock, Editor at Large -- Modern Materials Handling, 11/1/2008

Lift trucks and automatic guided vehicles (AGVs) are the workhorses of most warehouses and factories, and batteries provide the power that keeps these electric vehicles humming during a shift. Choosing the right battery and battery handling equipment can determine how long your workhorses run between charges and how long your batteries last before replacement.

The right battery for the job

The first step isn't choosing the type of battery to power your truck, but making sure you have the right size battery. “The battery is your energy source,” says Ed Price, manager of training and technical support for EnerSys Motive Power (800-538-3627, www.enersysmp.com). “You want to put as much battery into that compartment as possible.”

Too often, Price adds, users purchase a smaller battery to save money. But skimping may result in a short run time and require taking a truck or AGV out of service for a battery swap or charge during a shift, rather than between shifts. Ultimately, this reduces your productivity.

Changing

Automatic battery changing systems remove and deliver spent  batteries to a charging station and install fresh batteries from storage.

BATTERY TYPES

The most common battery type in use today is a flooded battery, also known as a wet cell battery. This technology dates back to the 1880s. Like a car battery, a flooded battery uses a mixture of water, battery acid and lead plates to conduct electricity. “A flooded battery is a very mature design that hasn't changed much in the last 120 years,” says Price. “It works because it is very forgiving, regardless of how it gets used.” But while the technology is more than a century old, there are a variety of product types to choose from.

Flat plate batteries: A flat plate is a grid consisting of a crisscross network of lead alloys that are filled in with an active material, providing a path to maintain electrical current. “Although suitable for any environment, a flat plate design is robust and performs well in abusive environments,” says Chad Christ, marketing coordinator for East Penn Manufacturing (610-682-6361, www.dekabatteries.com). “Each flat plate manufacturer offers product options depending on the application needs.”

Tubular batteries: Instead of the crisscross network of lead alloys used in a flat plate battery, a tubular battery uses a cylindrical lead spine for conduction. While more expensive than a flat plate battery, a tubular battery can generate more amp hours from the same size and space as a flat plate battery. “That allows more run time or more shift time,” says Price. “A user running one shift, five days a week may not see an advantage. A user running three shifts a day, six or seven days a week, however, will get a productivity boost.”

Low maintenance or reduced maintenance batteries: Two types of low maintenance batteries are common. Waterless batteries use special grid alloy combinations and separator materials that significantly reduce maintenance times and costs. Where a standard flooded battery requires watering every 1 to 2 weeks, waterless batteries feature a watering interval of 9 to 10 weeks. As they age, however, they require more frequent watering. Sealed batteries, also known as valve-regulated lead acid batteries, are maintenance free—they never require watering. These batteries are more appropriate for light-to-medium duty applications.

Opportunity charge batteries: These batteries take advantage of a charge that is higher than a conventional charge but less than fast-charging technology (see below). The lower charge allows the use of less expensive charging equipment than fast-charging technology without the need for an AC service infrastructure upgrade. The technology enables charges during breaks, lunches and other down periods. Still, users must perform a weekly full charge and equalize charge. Opportunity charge batteries are best to use in a single or two-shift operation with a light to medium workload.

Fuel cell power option: Given the emphasis on going green, it's no surprise that there is a great deal of interest in fuel cells and clean energy. A variety of designs are coming to the market, says Christ, including a hybrid design that includes a fuel cell module, absorbed glass mat batteries and a compressed hydrogen storage tank. “These batteries are completely interchangeable with standard lead-acid lift truck batteries and require no modifications,” says Christ. The limitation to the broad-based use of fuel cell batteries is the lack of an infrastructure for hydrogen fueling stations.

Regardless of the battery type, flooded batteries require maintenance. They need charging at the end of a shift; in multi-shift operations that entails removing, replacing and charging the spent battery. In large operations, that also may require a battery room to store charged batteries until they're put back into use.

Charging

All batteries, regardless of type, require charging, typically at the end of a shift.  Fast-charging systems deliver the charge four to five times faster than conventional charging solutions.

BATTERY MAINTENANCE

Choosing the right battery for your equipment and application is half of the equation. Maintaining those batteries is the other half. “With rotation and watering, we estimate you can increase the life of your batteries by 25 to 50%,” says Dan Dwyer, vice president and general manager for Sackett Systems (800-323-8332, www.sackett-systems.com). “What's more, you can reduce the number of batteries in your fleet.”

Battery handling systems make it easier, safer and more efficient for operators to swap spent batteries for fully charged batteries. Solutions range from transfer carts that simplify manual operations for companies making 10 or fewer battery changes per day to fully automated solutions that use automated storage and retrieval technology to manage 200 to 300 changes per day.

Next to charging batteries, watering a fully charged battery is the most important maintenance task. The heat created from charging and discharging causes the water inside a battery to evaporate, leaving behind the acid. “If you repeatedly charge a battery with low water, it will shorten the life of the battery,” says Ron Earl, marketing director for Flow-Rite Controls (616-583-1700, www.flow-rite.com).

With a watering system, the vent caps on the battery are replaced with caps connected by tubing that, in turn, is connected to a water source. When a cell is full, the valve automatically turns off. “What used to take 10 to 20 minutes per battery now only takes 10 to 20 seconds per battery,” says Julie Elliott, market manager for Battery Filling Systems (336-714-0448, www.batteryfillingsystems.com). While some systems use sensors and lights to monitor the water level in the battery and alert an operator when a battery needs watering, many facilities water on a schedule, typically after every five charges.

The last step in battery maintenance is battery washing. “As a battery charges, a sulfate deposit develops on the battery,” explains John Pratt, president of Multi-Shifter (800-457-4472, www.multi-shifter.com). “The deposits can build up and cause a short.” Battery washing systems offer a closed-loop system to wash away the deposits and filter the water, which contains hazardous contaminants. Pratt adds that the filtered water needs to be disposed of according to environmental regulations.

Even with proper maintenance, batteries eventually go out of service. An emerging technology known as lead-acid de-sulfation may add new life to old batteries. During recharging, sulfur bonds with lead in the battery, eventually forming a crystal that embeds itself into the lead plates, damaging the battery. A battery de-sulfator creates an electrical pulse that removes sulfation and restores the battery to its original state. “The system can restore a 3,000 pound forklift battery in two to three hours,” says Bruce Zeier, president of BravoZulu International (951-928-0595, www.battrecom.com). “Even batteries that have been sent to the graveyard can be restored to a serviceable condition.”

Watering

Next to charging, watering a fully charged battery is the  most important maintenance task to extend the life of a battery.

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