A number of powered access machines available in North America run on batteries. Push-around access platform models use a battery to power the platform elevation. Self-propelled units rely on battery power both for elevation and travel.
The most common batteries used are lead acid batteries. Using an electrolyte consisting of sulphuric acid, these cells can store impressive amounts of electrical energy in a relatively small space. This energy is stored in chemical form within lead grids mounted inside the battery. The reliance on lead grids and paste explains the great heft of lead-acid batteries.
When it comes to powering access platforms that primarily operate indoors, users can choose between two types of deep-cycle batteries: flooded and AGM. The long-standing “flooded” or “wet” batteries use a liquid electrolyte consisting of acid and water. It is by far the most commonly used battery for powering access platforms.
The more recently introduced absorbed glass mat (AGM) battery also uses acid electrolyte, but the electrolyte is in a more solid form. AGM uses a fiberglass like separator to hold the electrolyte in place. The physical bond between the separator fibers, the lead plates, and the container make AGMs spill-proof and the most vibration- and impact-resistant lead-acid batteries available today. AGMs use almost the same voltage set-points as flooded cells and thus can be used as drop-in replacements for flooded cells. Basically, an AGM can do anything a gel-cell can, only better. However, since they are also sealed, charging has to be controlled carefully, or they can be destroyed in short order.
Flooded batteries are popular because they work well and live a long time if properly maintained. Elke Hirschman, vice president of marketing for Trojan Battery, Santa Fe Springs, Calif., says, “While flooded batteries are the most economical, they require watering to ensure they operate at peak performance levels and sustain their rated life cycle.”
To help simplify maintenance of flooded batteries Trojan and other manufacturers now offer single-point watering systems that enable several batteries to be watered at once, instead of one by one. Hirschman says that single-point watering systems, such as Trojan’s HydroLink “take the mess and guesswork out of watering batteries.” She notes that HydroLink can fill a set of batteries in just 30 seconds.
A battery is only as good as the maintenance it receives, but making sure that batteries are maintained properly can be a real challenge—particularly when a lift is used in rental applications.
A trend noted by some of the access platform manufacturers is new options in batteries are becoming a coming trend in the industry.
“There are end users and rental fleets now requiring AGM batteries,” says Mike Buley, president of Absolute E-Z Up.
Likewise, Justin Kissinger, marketing manager of Custom Equipment says, “AGM battery options have been offered to reduce overall maintenance of the machines and to increase return on investment.”
Skyjack, one of the largest producers of DC-powered scissor lifts, is not convinced users are making a major shift to AGM battery use. Brad Boehler, president of Skyjack, says, “We have only had one of our bigger buyers indicate that they were shifting to an all maintenance-free battery fleet.”
Why would a leading supplier of AWP equipment make this major shift?
For as long as I have been involved in the rental industry, the Holy Grail was a truly maintenance-free, deep-cycle battery that could handle the demands placed on a piece of access rental equipment. Lead-acid batteries are, when properly maintained, a dependable and cost-effective way to provide energy. But the reality is that the batteries on jobsites do not always get the kind of rehydration they require. The result is batteries will need to be replaced much earlier than their expected life cycle.
You don’t have to boil a battery dry many times to cut its life expectancy in half. It can be difficult to identify the party that failed to properly hydrate a set of batteries. In many cases, the rental company ends up in a fight with a customer over the cost to replace a set often eating the cost outright to avoid losing the client.
So what is the real cost to replace a set of four lead-acid batteries? If it happens on a jobsite, it could entail two trips by a service tech. Add the time to the cost of the batteries, and in some cases, you could exceed $1,000. That is nearly 10 percent of the original cost of the machine.
The price point
Now that it appears AGM is an acceptable alternative, the issue becomes pricing. If you consider the costs to maintain a lead-acid battery, the corrosive properties that accompany it, and the potential for improper maintenance, the battery could be replaced as early as 30 months into its life. With that in mind, the added upfront costs of an AGM product could provide a superior return on investment.
This investment consideration becomes more attractive when you consider that the serviceable life for electric lifts is being extended out to six or seven years. Based on research, AGM batteries can survive these extended lifespans.
Also to be considered are the environmental advantages of AGM. The higher charge efficiency of AGMs allows you to recharge with less energy: Flooded cells convert 15 to 20 percent of the electrical energy into heat instead of potential power, where AGMs convert as little as 4 percent. There is also virtually no gassing under normal operating conditions. Unlike flooded cells, AGMs are hermetically sealed and operate under pressure to recombine the oxygen and hydrogen produced during the charge process back into water.
If equipping a standard 20-foot scissor lift with a set of four AGM batteries adds $500 to the acquisition price, it is hard not to see the economic, environmental, and service advantages they would seem to provide.