Lift Truck Tips: Don’t judge a battery by its state of charge

For too many lift truck fleets, battery management habits are not so different from those that keep the family point-and-shoot camera up and running. There’s a collection of batteries in the closet somewhere and as long as one of them has enough juice for a picture, all is well.

But even those facilities working to track information about their battery inventory’s age, state of charge and usage are challenged to achieve per-battery visibility. Many have recognized that a battery can have a substantial impact on productivity and costs, but the problem is more nuanced than that. Each standard, lead-acid, 24-volt lift truck battery is made up of 12 cells, or 24 cells for 48-volt batteries. Therefore, if not effectively managed, each battery offers at least a dozen ways to shorten its own life, keep a lift truck and operator from working, increase maintenance costs and slow or halt production.

“It is not an exaggeration to say that a single bad cell can propagate into the entire operation,” says Roger Tenney, director of business intelligence for I.D. Systems. “If you identify a bad cell, service it and bring that battery back to health, you can get 25% more out of that battery, both in terms of runtime and lifespan.”

Tenney offers the example of a customer who deployed a system to uniquely track each battery. Two seemingly identical batteries were introduced into the system, and both went into the field at 100% state of charge. After virtually identical usage, operators returned the batteries to the battery room once each battery had been run down to 25%. One battery had produced 5.5 hours of run time, and the second only 3.5 hours. The difference was a bad cell or two.
“Once the battery goes bad, it’s a boat anchor on the entire operation,” Tenney suggests. “Some assume batteries die in four years, and they suppose they should buy some new ones each year. They can extend that by a year or more.”

In an effort to increase efficiency and accountability in the battery room, facilities where operators were once allowed to change batteries themselves have installed a dedicated employee to oversee exchanges. With per-unit battery management and basic displays, new systems can direct battery swaps even more efficiently while maintaining auditable data. By connecting with lift truck and operator data, the battery management system can identify specific operators in need of additional training.

Access control is a valuable tool, especially since Tenney says even small disruptions can have a big impact. “We’ll often see third-party contractors get on a lift truck and use it like personal transport over the weekend,” Tenney says. “Come Monday, there could be unaccountable damage, vehicles left wherever and the battery left low.”

Over time, battery management should create a battery inventory of about 1.05 batteries per truck, or five spare batteries for every 100 lift trucks. Tenney adds that data can help managers associate consumption of charge with productivity and expected performance.

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