Discharging battery misconceptions
October 1st 2005

In light of spiralling energy costs, how can warehouse managers reduce the day-to-day running costs of electric warehouse materials handling equipment?

According to Energywatch, the gas and electricity watchdog, energy costs for British businesses have increased by approximately 60% during 2005. With the outlook for 2006 following a similar trend, it is critical that warehouse operators understand the implications of these cost rises and the effect on electric forklifts.

"Like all pieces of warehouse equipment, batteries require proper maintenance and management to prolong service life and increase efficiency. If they are not maintained and handled correctly they cannot perform to their potential," states Ian Bennett, national accounts manager at Finning Materials Handling.

"A traction battery has approximately 1500 charge cycles within its lifespan, which is approximately four and a half years of costeffective performance. However, the lifespan can be significantly depleted as a result of unnecessary damage and incorrect charging," continues Bennett.

There are a number of common traits that operators and warehouse managers are guilty of when working with batteries.

Reduced productivity

Larry Blackwell of Enersys motive power comments: "All too often, operators view a machine to be working at optimum performance when a battery’s power is full and also believe that ‘opportunity charging’ is the most effective way of maintaining a truck’s efficiency. This is a myth. Users who opportunity charge a forklift are significantly reducing the life of the traction battery.

"If a battery is opportunity charged on a regular basis, in time warehouse managers will begin to see some notable problems as the machine is unable to complete its shift pattern. The resulting effect is reduced productivity within the warehouse, and if this problem persists it may result in a new battery unit being required well before the normal life expectancy of the battery. This is a huge and unnecessary cost especially if calculated over an entire fleet," states Blackwell.

An additional problem for many electric truck users is the tendency to leave battery chargers switched on when not in use, with the operator simply removing the charge lead from the battery when finished. As soon as the connection is broken between the battery and the power source, the battery shorts out, but maintains a small enough charge to light the LED on the charger.

Consequently, when the next operator plugs his battery into the charger, the power supply LED lights up, showing the state of charge from the previous machine.

The operator believes the battery is charging, and so the following day when the battery power is low, is forced to ‘opportune charge’ at various intervals to maintain power. This process not only increases downtime but also reduces the life of the battery, using three-to-four battery lives as opposed to just one.

To safeguard battery life and control usage costs, there are a number of simple guidelines that operators and warehouse managers should follow.

"Battery best practice should be developed within the warehouse environment, to ensure that the truck fleet is working efficiently on a day-to-day basis. Managers should stipulate that batteries must be charged at the end of a shift, for improved efficiency. To provide an optimum charge, the battery should be charged for eight hours with an additional cooling period within a 24 hour period, to ensure that the battery is restored to full power for the next day," says Bennett.

Blackwell continues: "A battery performs at its best if discharged to no more than 80% of its rated capacity and then re-charged on an uninterruptible charge for approximately eight hours. If charged and maintained correctly the battery will perform to the length of the battery manufacturers warranty agreement, covering the batteries for up to 1500 charge cycles."

The best way to ensure that batteries are not overcharged is to test them every month.

Enersys advises that at the end of a charge, the temperature of the centre cell should be measured, if the electrolyte is more than 36°F above the ambient temperature, a battery technician should be called.

Scheduled downtime

Keeping regular records of a machine’s maintenance is also an invaluable source of information when it comes to predicting the replacement dates for machine components.

These should include when the battery is watered, and the temperature of the battery at the end of a charge. With these records in place, it is much easier to schedule downtime for a truck’s service or repair, ensuring the efficiency of the warehouse is maintained.

Energy costs can be reduced within the working environment through the adoption of battery best practice, additional savings can be made when re-charging batteries through the use of high frequency chargers.

However it is important to note that opportunity charging is not an effective way of charging batteries and will add to energy costs.

Bennett concludes: "At Finning Materials Handling, we acknowledge the importance of battery best practice for the continued efficiency of a warehouse environment.

Battery efficiency has become an essential part of warehouse management, as utility costs have continued to spiral. Critically, if operator working practices are improved and battery best practice is stipulated, warehouse managers will begin to see a steady reduction in energy and maintenance costs of materials handling equipment and, as a result, a rise in warehouse efficiency."

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