Future technologies
FUTURE TECHNOLOGIES
Some companies, including Toshiba (2008) and Power Technology (2007) have announced that they plan to manufacture prototype batteries of proprietary, patented, new technology. These batteries are anticipated to be up to 50% lighter and contain significantly less lead than conventional batteries. Additionally these batteries should also have superior recharge rates and lifetimes. Power Technology's new battery is comprised of electrical current collectors constructed of reticulated vitreous carbon covered with a thin layer of a lead tin alloy, which create up to four times higher surface area for electrochemical reactions compared to those in a typical lead acid battery. This results in a battery with higher efficiency and higher capacity, meaning more electricity is stored and delivered in smaller package.
What about fuel cells, one might ask? Although the hype surrounded by this new electricity marvel was high flying, the reality is more on the ground. We saw some of the prototypes, but they are expensive, have problems with high voltages (can't handle peaks), and especially, with all the toxic/explosive materials are not considered safe (not in post 9/11 world anyhow)…
Improvements
People who use power wheelchairs have asked for improvements in battery technology, however, the technology remains mostly unchanged. This is partly because of the relatively low number of power wheelchairs purchased — about 500,000 per year — when compared to automotive applications — about 6.6 million per year by a single manufacturer. Also, because of limitations in the health care market (e.g. Medicare, Medicaid, private insurance), there is not an incentive for manufacturers to develop new battery technologies since they may not be reimbursed for batteries other than lead-acid batteries. Currently, only lead-acid batteries are reimbursable by Medicare and Medicaid. If a battery has a greater capacity, a longer range, greater power potential, it may not be paid for because it is not necessary under the definition of "medical necessity," even if the increased benefits outweigh the increased costs.
Alternatives to the lead-acid battery do not presently exist in the traditional power wheelchair market, even though the potential for new technologies do exist. Yamaha is marketing a power assist system for people who use a manual wheelchair. The motors are built into the hub and assist the individual as he/she pushes on the pushrim. Nickel/Metal Hydride (Ni-MH) is used in place of lead-acid batteries. Unfortunately, this wheelchair system is only available in Japan. Other alternatives to lead-acid batteries may be seen as automobile manufactures try to find more environmentally friendly alternatives to gasoline and diesel fuel. Also, alternatives may rise from the personal computing industry where a premium on capacity and range are present for laptop computers. Some of the alternative batteries are Nickel/Cadmium (Ni-Cd), Nickel/Metal Hydride (Ni-MH) and Lithium Ion. Finally, the replacement of batteries with flywheels has been examined as a power source for both the automobile industry and the power wheelchair industry.
The main characteristics of the deep-cycle lead-acid battery are its capacity (expressed in ampere-hours or Ah), its current rating (expressed in amperes or A), the type of cell (wet or gel), and the type of charger. Generally, the larger the battery, the larger the capacity and the greater the range. The larger the current rating (current is the rate of flow of electrons), which is dependent on the speed of the chemical reactions within the battery, the more torque which can be generated by the motor. This translates into the ability to traverse rough terrain. The type of cell will depend on the primary use of the battery, as described previously. Finally, the charger will depend on the type of battery selected and the country in which the wheelchair will be used.
