Charge! Getting the Most out of Your Batteries

by Kathy Wechsler on January 1, 2006 - 3:20pm

QUEST Vol. 13, No. 1

Your battery system is the fuel tank of your power wheelchair. The fuel it carries is an electrical charge, which needs to be kept full so it can operate.

Wheelchair and scooter batteries are called deep-cycle batteries, meaning that they require constant discharging and recharging. (By contrast, the battery that starts the engine of your car recharges itself as you drive.)

“A deep-cycle application is like a trolling motor in a fishing boat, where you run the little motor fishing all day long and then once you get home you recharge it,” says Craig Starkey, service manager for Travis Medical Sales in Austin, Texas.

“You deeply discharge the battery before you recharge it. Same thing with a wheelchair: You use it all day long and then charge it at night.”

The facts of life

Virtually all scooters and wheelchairs use two 12-volt batteries, which produce 24 volts.

Since the batteries act as your wheelchair or scooter’s fuel tank, it makes sense that the larger the fuel tank (battery size), the more fuel (power) it can hold, says Dennis Sharpe of MK Battery, a leading battery distributor to mobility equipment dealers. (The company doesn’t sell directly to the public.)

In keeping with this theory, a U1-sized battery system, which is used in most scooters and inexpensive power chairs that don’t need to travel long distances, is half the size of a Group 24 system. If your chair uses a lot of power because you need to have a greater range, then a Group 24 is for you. The size of the 22NF battery system is between the U1 and the Group 24.

“A [chair’s] amp-hour rating gives an indication of how much energy the battery is designed to hold,” says Sharpe, who’s been with MK Battery for 18 years. “It’s like measuring how many gallons of gas an automobile fuel tank can hold. It won’t tell you how many times, cycles, the tank can be refilled so it is not a measure of longevity.”

The owner’s manual that came with your wheelchair or scooter will tell you which battery to use. Sometimes the manufacturers will give you an option, and if that happens, Sharpe advises getting the bigger battery system for greater longevity and performance because it can hold more energy.

Who’s in charge?

Sharpe recommends that you charge your chair according to how often you use it and the wear and tear you put on it. Never let the batteries run all the way flat, he says. The deeper the discharge, the harder it is on the batteries when you go to recharge them.


Let’s say that you only use your power chair occasionally. Since you’re not putting much running time on the chair, you can charge every two or three days without running down the batteries. On the other hand, if you run your chair 12 miles every day, you should charge it daily.

“Any time there’s doubt about how often you should charge, it is better to err on the side of daily charging,” Sharpe says. “No one should ever become stranded because partially charged batteries did not get them home.”

But the number of hours isn’t the only measure of how hard your batteries work. That also depends on how you use the chair.

Maybe you use it for eight hours every day, but you always stay indoors. Your friend only uses his power chair to walk his dog for two hours a day, but he takes his dog up steep, rocky hills. Even though you use your chair for more hours, your friend’s going to have to charge his batteries more often because he works them harder.

“Batteries take some time before they begin to absorb the energy the charger is trying to provide,“ Sharpe says. “We feel that a longer charge time allows a better chemical process which benefits the entire battery.”

Some chairs will tell you when you need to charge the batteries by the light on the fuel gauge. When the light changes from green to yellow, it’s usually time to charge.

Some newer power chairs have a multicolor battery display located on the chair’s controller. The display consists of green, yellow and red bars.

“To get into a good habit, I tell people to try and drop the green bars off the graph before they recharge,” Starkey says. “If that’s every other night or every third night, get into that routine.”

Time for a change

How do you know when it’s time to get new batteries?

“Usually they start to fail because of their age, and their performance starts to drop,” Sharpe says. “I think that in general, people know when all of a sudden the chair or scooter is not running quite as strongly at the end of the day or they are not getting quite as far.”

Starkey says that older batteries usually don’t fail without giving you some warning signs, such as decreased running distance between charges. If all of a sudden your new batteries go dead, you have a defective battery.

“All battery manufacturers warranty against manufacturing defects,” Sharpe says. “This warranty is given to the dealer, who should determine if the problem is actually battery-related.”

Before replacing your batteries or letting a technician talk you into replacing them, consider how they’ve been performing, Starkey says.

“If you put your chair in the shop for new tires or whatever and all of a sudden they say you need new batteries, I’d ask, ‘Why do you think I need new batteries?’ They say, ‘They’re a year and a half old.’ And you say, ‘Well, so what, they’re working great.’”

Shopping for batteries

To buy and install replacement batteries, both Starkey and Sharpe suggest that you visit a DME (durable medical equipment) company with a service department. These technicians have the proper training and can find the best batteries for your needs.

Positive and negative charge

It’s never a good idea to buy wheelchair batteries online or from a battery distributor and install them yourself unless you’re an expert.

Starkey says to beware of battery distributors that want to install your batteries, because they don’t specialize in wheelchairs.

“You go to your average battery distributor, and they sell you batteries all day long, but they don’t know anything about your wheelchair,” he says. “They may not even know how to get it apart to put the batteries in, and the last thing you want is somebody messing up your chair.”

A DME technician may even find that the batteries aren’t the problem, Sharpe says. He or she will be able to tell you where the problem comes from or if you have a faulty battery charger.

When you get new batteries, the cost depends on the size of the batteries and how much work is involved in the installation process.

Installing a U1 system can cost from $150 to $250, depending on how easy the batteries are to access. Specialty seating such as tilt and recline systems make the batteries difficult to access.

You can expect to pay up to $500 to buy and install a Group 24 battery, depending on ease of access.

Medicare, Medicaid and most insurance providers cover a percentage of the cost. MDA also pays up to $500 per year for wheelchair repairs and modifications, which include the purchase and installation of batteries.

It used to be that you could only buy lead acid batteries. These liquid electrolyte batteries have to be maintained by monitoring the water level and refilling with distilled water. A messy job, especially when an acid spill causes corrosion.

Acid can easily leak from a crack in the battery case, eating away at your chair’s electronics and damaging whatever’s around it. This causes problems for airline travel: Lead acid batteries have to be removed from your chair and placed in a spill-proof container before it can be put on the plane.

Thankfully, technology has improved battery systems.

“We don’t deal with [lead acid batteries],” says Craig Starkey of Travis Medical Sales. “All of our wheelchair manufacturers recommend sealed, maintenance-free batteries in their chairs.”

Sealed batteries were introduced in the early 1950s and have gradually replaced lead acid batteries. For starters, they’re spill-proof, easy to maintain and approved for airline travel. There are two types of sealed batteries: sealed lead acid (SLA), synonymous with absorbed glass mat (AGM), and Gel, which is also a sealed lead acid product.

In SLA batteries, the electrolyte is liquid, but the batteries are sealed so the acid can’t spill or leak out. Gel batteries, in which the electrolyte is a gel, give a longer life expectancy and better performance than SLA batteries. These are excellent for users who travel long distances.

“There’s no more demanding an application for a battery than a power wheelchair, because we’re looking at 16 hours a day, seven days a week,” Starkey says. “Only the best of batteries are going to hold up to active users.”

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