Is there a better way to charge the batteries in your electric lift trucks and tow tractors? Or to keep these power sources in automatic guided vehicles "electrically topped up" so the AGVs remain running with no long timeouts for charging?

Perhaps there is. Fast charging equipment may be the answer.

Charging times of 6 to 8 hours followed by a cooldown period of as long as 8 hours are history with fast charging. But how fast is fast? It's hard to say, precisely. Much depends upon how long and how hard each vehicle runs over a day, how often there are times to opportunity fast charge.

PosiCharge says its multi-vehicle, parallel charging equipment will get batteries operational again as soon as 5 to 10 minutes. To go from a 20% state of charge (SOC) to an 80% SOC takes 20 to 60 minutes, however.

Edison Minit-Charger notes how its sequential system can recharge – return ampere-hour capacity to a depleted battery – at a charge current level up to four times higher than conventional chargers.

Batteries undergoing fast charging also need time for a daily full charge and for equalization charges. Typically, that equalization charge is applied at least once weekly.

"Fast charging," says Peter Michalski, product director, Edison Minit-Charger, "provides benefits to those who charge batteries often throughout the day." As he explains, "Providing precise battery charge control and striking a balance between the fast charging system and the customer's operation create the value. It's not just a case of jamming more electrical power into a battery faster."

Use of the technology eliminates the need for costly battery rooms and frequent battery changeouts, for example. Fast charging a vehicle battery can occur right in the plant floor area where the lift truck operates, not in some distant battery room.

Among the reasons one auto manufacturer chose fast charging technology, says Larry Hayashigawa, PosiCharge product manager, was added safety. With dedicated fast chargers in the work cell where forklifts operate, vehicle travel outside the cell has been minimized, lessening the risk of accidents.

"Training of lift truck operators is a big issue," however, adds Hayashigawa. Some operators never have had to charge their vehicles previously.

But once they learn about fast charging and work with it, the PosiCharge exec adds, "they like it. They don't waste their time waiting in line for a recharged battery from the battery room."

Whether fast charging will work cost effectively for a fleet of electric trucks, tuggers, or AGVs depends upon a number of factors.

To begin, fast charging technology only works with flooded, lead-acid batteries with voltages from 24 V to 96V. But if your vehicles only use maintenance-free, sealed batteries, then this technology isn't for your fleet – at least yet. Heat buildup and transfer of this residual heat in sealed batteries are among the issues that are being studied. Flooded batteries handle heat buildup far better than do the sealed batteries.

Other factors that need to be considered include:

• The kinds of batteries used,
• The numbers of trucks in the fleet,
• How many shifts the trucks operate on daily and how often batteries are swapped out,
• And how hard the vehicles work in lifting and moving loads, discharging their batteries.

In general, fast charging is not likely to be a very cost-effective solution for those operations with only one, two, or three trucks, and where vehicles are lightly used.

How often the user changes batteries per truck per day is the key issue. As Edison's Michalski suggests, one simple rule of thumb is this: If a forklift requires approximately one battery change per shift, then the end user can profit from fast charging.

To further illustrate the potential benefits from the new fast charging technology, let's contrast traditional or conventional charging with fast charging. No doubt you're familiar with some of the conditions that the traditional technology requires of its users.

Conventional charging requires investments in both charging and battery handling equipment. There are also the labor hours spent by operators and/or maintenance workers in changing and charging batteries, and also in watering them.

With fast charging, you still invest in charging devices. But you can do away with the battery room and especially with virtually all of its battery changeout equipment. One battery, one vehicle is the basic premise of this kind of charging.

Labor savings result because batteries aren't swapped, moreover, until their useful life has ended. And many of the dangers of frequently handling heavy, potentially corrosive batteries are avoided.

A single battery remains onboard each truck in fast charging, even through the same forklift may be used over multiple shifts. The forklift's battery is fast charged in the vehicle when there are opportunities to do so: at operator mid-shift breaks and lunch periods, at shift changes, and at other times when the vehicle isn't in use.

Do note that this is opportunity fast charging as compared to opportunity charges with conventional chargers, which is a much slower regenerative process for a flooded, lead-acid battery.

Fast charging restores ampere-hour capacity more rapidly to a battery than does conventional charging. Charge current is up to four times higher in fast charging.

With conventional chargers, a depleted battery receives a restorative charge for 6 to 8 hours typically. Then the battery rests and cools down for another 3 to 8 hours before it's ready to go back into service. In effect, this battery can work only one shift a day.

In contrast, fast charging can keep a multishift operation with an electric vehicle fleet of four or far more trucks up and running very productively. And it does it without changeouts.

Fast charging is "a bottom-up approach to safely maintaining all the batteries in a fleet in the sweet spot for power capacity: between 40% and 80% state-of-charge," says Edison's Michalski.

Far fewer batteries need to be kept in inventory at any point in time for these fast-charged, multishift operations, moreover. Yet don't be mislead in thinking that you'll save by purchasing fewer batteries over the long haul.

Batteries that are fast charged and put through two charging cycles per day, for example, will have a shorter lift expectancy, says PosiCharge's Hayashigawa. They might last only 3 years instead of 5 years, he points out. From a life cycle perspective, roughly the same number of batteries will be used for either conventional or fast charging, he maintains. But you don't have to buy them all at once with fast charging.

Three manufacturers of batteries offer warranties for their new batteries when used in fast charging operations as of press time. They are Crown Battery, East Penn, and GNB Industrial Power. Other major battery makers are expected to follow the lead of these three firms.

Potential users of fast charging technology will want to read the fine print of these warranties before switching over to this equipment, and when purchasing new batteries.

For fast charging, batteries require minor modifications such as additional charge cables and double cell interconnects. Both Edison and PosiCharge also require that fast charged batteries be equipped with each firm's proprietary battery module. The modules sense and measure battery conditions such as voltage and temperature. They also provide historical data on the unit being charged to the system.

New batteries so outfitted are preferred in system installations by both of these fast charger system suppliers. But as Edison's Michalski says, "even one- or two-year old batteries can be fast charged," when properly equipped.

Click on this icon to read more about fast charging and its costs, as well as battery handling.