August 3, 2018
material handling | Charging Systems

Start me up: Opportunity charging or fast charging?

Start me up: Opportunity charging or fast charging?

Both methods are designed to get DC equipment up and running faster—and keep it running longer—than with conventional charging. So which is best for your operation?

By Victoria Kickham

Demand for longer-running lift trucks has given rise to opportunity charging and fast charging of batteries, both of which are aimed at expediting the charging process, reducing downtime, and freeing up space for other activities when compared with conventional charging. The ultimate goal? Getting warehouse and DC equipment started up even faster and running longer throughout the day to increase productivity.

While interest in both methods is creating industry buzz, it's also driving the need for increased education on the part of battery and charger manufacturers and their dealers. "It's common for customers using conventional charging to want to go to opportunity or fast charging, but they don't know if it's a good fit," says Jeff Harrison, business manager for Troy, Ohio-based charger manufacturer Ametek-Prestolite Power. As a result, suppliers say they're spending considerable time going over the what, why, and how of opportunity charging and fast charging with customers.

So what do these terms mean and how do the various methods stack up? What follows is a look at the key differences between conventional charging, opportunity charging, and fast charging and what may be right for your operation.


In a nutshell, opportunity and fast charging speed up the battery charging process. Along the way, they also help eliminate some of the labor and maintenance associated with conventional charging.

For most of battery history, conventional charging was the only way to charge a lead-acid lift truck battery. Simply put, with conventional charging, a facility has one or more batteries that are "changed out" when they are drained of power—that is, they are removed from the lift truck and connected to a charging system. The batteries are charged for eight hours, cooled for eight hours, and then put back into use. The process requires a designated battery space where charging and other maintenance activities are performed. Depending on the operation, the process could take up considerable real estate inside a warehouse or DC—not to mention the time and effort needed for the change-out process, and the need for multiple batteries for heavy-use and/or multiple-shift operations.

"That was the traditional way we did it up until 15 years ago," Harrison explains. "Then, some smart people said, 'Let's recharge faster so we don't have to take [the battery] out of the truck.'"

The result was opportunity charging, which is done throughout the workday when the lift truck is not in use—during lunchtime and other short breaks, for example. With opportunity charging, the battery remains in the lift truck and is plugged into a charger; larger facilities often have banks of charging stations for this purpose. Maintenance is reduced—no more changing, charging, and cooling of multiple batteries throughout the day. Instead, maintenance is performed weekly and monthly, including a regular equalize charge.

But the story doesn't end there. "Then, [researchers] said, 'Let's increase the rate so we can charge it even faster," Harrison says. "And now we have fast charging."

Like opportunity charging, fast charging is done throughout the day, without removing the battery from the lift truck. The key difference between the two methods is the start rate when charging the battery; start rate refers to the amount of current you're putting back into the battery at the start of the charge. As Harrison explains, charging happens on a curve, with the most current going in at the start before tapering off and ending at about a 5-percent rate. Speeding up the charging process happens at the beginning of that cycle. Quite simply, fast charging utilizes a faster start rate, further accelerating the charging process so that you get even more use out of your equipment per shift.

As an example, consider a 1,000 amp-hour battery. The start rate for conventional charging is about 20 percent, meaning that you're putting 200 DC amps back into that battery at the start of the charge. The start rate for opportunity charging is about 25 percent, meaning that you're putting 250 DC amps back into the battery at the start. The start rate for fast-charging applications is 35 percent or more, Harrison says.

Speeding up the charging process via opportunity charging and fast charging allows the lift truck to be used more continuously throughout a shift and for multiple shifts, often allowing facilities to reduce both the number of batteries and the amount of equipment they need. Thus, the cost savings add up: in lower capital expenditures, higher productivity, and lower maintenance costs.


Although the pros of opportunity and fast-charging methods are pretty clear—cost savings, higher productivity, and safety and maintenance improvements—experts caution that the methods are not for everyone. As Mike Hagen, vice president of sales and marketing for Menomonee Falls, Wis.-based battery and charger maker Storage Battery Systems LLC, explains, opportunity charging simply means that you're charging the battery more often and using higher charge currents to keep your equipment up and running. This can be ideal for operations running multiple shifts, as it allows them to save the time spent changing out, charging, and cooling their batteries daily.

Likewise, fast charging may be ideal in situations with heavy equipment use—for example, an automotive plant running six days a week and looking to reduce liability concerns associated with employees frequently changing out large, heavy batteries; free up valuable floor space previously needed for battery changing rooms; and reduce labor costs by eliminating time lost changing batteries.

But there is one big "con" with both methods, and it can outweigh the benefits if the conditions aren't right: reduced battery life.

Think of your battery as a car that will run a certain number of miles before it wears out. The faster you put those miles on, the sooner you will need to replace it.

"Batteries still have a finite [amount of use]," Harrison explains. "Opportunity charging and fast charging don't change that."

In fact, they can accelerate the process by exposing the battery to more heat, which can wear it down faster.

"You still get the same amount of work out of the battery, you're just getting through the life of the battery faster because you are using it more," Harrison explains, adding that proper care and monitoring is crucial to getting peak performance out of any lead-acid battery, regardless of the charging method. "That's taking a while for end users to grasp. Instead of getting five to seven years out of [a battery], you may get a year less."

Hagen adds that while both opportunity charging and fast charging shorten the life of the battery, fast charging is the quickest way to wear the battery out.

"You're going to have to change out the battery sooner by fast charging or by opportunity charging—but you'll have to replace the battery even sooner with fast charging," he says, adding that fast charging equates to overcharging the battery, which hastens its ultimate demise. "The benefits of fast and opportunity charging are getting amp hours back into the battery throughout the day versus getting a full depth of discharge and recharging fully. The negative is ... that it's just not good for the battery."

But again, the risk makes sense in certain situations—especially when balancing the cost of reduced battery life with investing in multiple batteries and equipment up front. Smaller operations running one shift are unlikely to see the same productivity gains from either opportunity or fast charging that their larger counterparts running multiple shifts will—especially if they're using equipment less or for lighter-duty tasks. Such operations may end up shortening battery life unnecessarily, Hagen says.

It's worth noting that fast charging makes up a small portion of the battery and charger market today. Harrison estimates that fast chargers represent less than 10 percent of the market compared with conventional and opportunity-charging systems. Opportunity charging is far more widespread, Hagen and Harrison agree.


Weighing the pros and cons of conventional charging, opportunity charging, and fast charging is no easy task. That's why Harrison, Hagen, and others recommend that customers begin with a "power study" of their facility's equipment and environment to determine the best option. Such studies are usually conducted by a battery/charger dealer and utilize monitoring equipment placed on all batteries in use. Using sensors and software, the monitoring system tracks conditions such as amp-hour usage and idle time. The dealer also considers how the equipment is used and the environmental factors at play—such as temperature and humidity—as well as utility costs and related issues.

Brian Faust, general manager for Reading, Pa.-based battery, charger, and accessories maker Douglas Battery, says such studies can make or break a company's charging optimization initiative. Douglas Battery recommends running a power study for two weeks, although 30 days is preferable if time allows, to establish the best charging method and equipment required.

"There is no particular market segment best suited to fast charging or opportunity charging. It all depends on a particular customer's demand out of their equipment," he explains. "And the power study is the key to determining which of the three [methods] is quoted. Not doing one and just selling a customer a program can mean that they don't get the results they want, or that they spend too much or too little ...

"You have to be able to do your due diligence. If you're not doing power studies, you're not doing your customer justice."

About the Author

Victoria Kickham
Senior Editor
Victoria Kickham started her career as a newspaper reporter in the Boston area before moving into B2B journalism. She has covered manufacturing, distribution and supply chain issues for a variety of publications in the industrial and electronics sectors, and now writes about everything from forklift batteries to omnichannel business trends for DC Velocity.

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