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In recent years, “lithium-ion battery” has become a high-tech catchphrase, suggesting a compact, high-energy battery used in consumer electronics ranging from laptop computers to power tools to hybrid vehicles.

Understandably, power wheelchair users have been intrigued by the promise of lithium-ion technology. After all, a lighter battery with double the driving range of a conventional deep-cycle battery would unplug many with disabilities from the restrictions of a charger cord, allowing them to travel farther per charge than ever before – a life-enhancing benefit.

However, with lithium-ion technology so readily used in consumer products, why isn't it immediately available in power wheelchairs, or when will it be, especially if it's so promising?

Lithium-Ion as a Catchphrase
Interestingly, when we hear the term “lithium-ion” it's often misused. Lithium-ion is a battery technology in itself, but just one of a whole class of “lithium-derived” battery technologies. What's more, a true lithium-ion battery is among the least stable forms of lithium-derived technologies, one that, when mistreated, can be extremely dangerous (the 10-million consumer electronics batteries recalled in mid-2006 because of explosions were traditional “lithium-ion” technology).

In an effort to resolve safety issues of traditional lithium-ion technology, “lithium iron phosphate” variations have been evolving, developed by universities and private industries alike. Since 2005, commercial products ranging from the Segway scooter to DeWalt power tools to PHEV hybrid car applications have all used lithium iron phosphate variations to provide safer lithium-derived batteries.

Therefore, it's important to recognize that “lithium-ion” batteries aren't what's used toward most modern battery applications, but the safer “lithium iron phosphate” variations.

Lithium-Derived Batteries and Power Wheelchairs
With lithium iron phosphate battery variations proving successful in consumer products – on average, 33% lighter, with twice the energy of a comparably-sized conventional battery, with a 5-year lifespan – the question then becomes, why aren't they currently used in power wheelchairs?

The answer comes down to three foremost factors: Testing, compatibility, and cost.

Firstly, despite the promising performance and safety to date of lithium iron phosphate battery variations in mainstream products, their testing in medical devices is ongoing. While we are seeing lithium iron phosphate battery variations enter the mobility market toward applications like powering vehicle lifts, it's a larger leap into an ultra-critical, “user confined” device like a power wheelchair where reliability and safety are paramount – so exceptional testing must continue before coming to market.

Secondly, most power wheelchair electronics aren't presently designed to seamlessly interface with lithium iron phosphate batteries. Lithium iron phosphate batteries feature different voltage and charging characteristics than lead-acid batteries, and if they're simply placed in most existing power wheelchairs, issues arise, from as simple as an inaccurate battery gauge reading, to as disconcerting as overheated connections. Therefore, although there are self-described plug-n-play lithium iron phosphate “Group-24” batteries on the market today from the industrial and marine industries, power wheelchair electronics aren't yet designed to accept them predictably, and simply plugging in a set of lithium iron phosphate batteries into an existing power wheelchair proves problematic. Therefore, power wheelchair electronics need to be enhanced for compatibility with lithium-derived battery technology.

Lastly, and arguably the biggest long-term hurdle, lithium iron phosphate battery variations remain extremely expensive. While a pair of Group-24 lead acid batteries cost approximately $400, a similarly-sized pair of lithium iron phosphate batteries is approximately $3,500. Consumers struggle to fund basic mobility products – and often have to fight insurers for it – so $3,500 for batteries is simply out of consideration for most, as there's simply no way to fund them.

But, the Future is Near
Fortunately, evolving battery technology is among the biggest global high-tech trends, where environmental concerns are driving a push toward better, safer, less-costly battery technologies. And, there's no doubt that battery advancements are trickling toward mobility products, where the benefits of the technology and lower costs continue opening the door for entrance into the mobility market. In this way, it's not a question of if advanced battery technology finds its way into power wheelchairs, but merely a matter of when. The good news is, we're all getting closer every day.

Published 11/09, Copyright 2009,