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Last month, Clinical Corner re-visited the topic of batteries in power wheelchairs and provided an update regarding sizes and types of batteries and battery chargers. If you missed the Power Wheelchairs: Batteries article, click here to read it. This month, Clinical Corner will address the topic of battery maintenance to answer the questions I often receive about how to care for batteries in power wheelchairs.
AGM (Absorbent Glass Mat) and gel batteries used in wheelchairs are sealed, deep-cycle batteries. Because the batteries are sealed, they do not require maintenance in the sense of adding water to the battery, which is required in wet-cell batteries. AGM and gel batteries require the use of optimal charging and storage practices.
Charging Wheelchair Batteries
Wheelchair batteries are different than car batteries. Whereas car batteries are designed to give a quick burst of power to start a vehicle, wheelchair batteries are designed to provide a constant source of power for a prolonged period of time while operating a power wheelchair. Just as it is important to have the correct batteries in the wheelchair, it is important to use the correct battery charger for the batteries and to follow the directions for connection contained in the manual that comes with the charger.
A new set of wheelchair batteries requires a "break-in" period, particularly if they are gel batteries. During the break-in period the gel batteries cannot accept a full charge, which means that the range will not be at the full capacity when the batteries are new. While some sources indicate that this break-in period is the first 6 to 12 discharges/re-charges, one battery manufacturer specifies this period is the first 15 to 20 charge cycles (MK Battery, 2009). In order to improve the long-term performance and longevity of the batteries, it is important to fully charge the batteries during this conditioning period.
If a power wheelchair will be used daily, the batteries should be charged overnight and the power to the wheelchair should be turned off while the batteries are charging. The battery charger will indicate when the batteries are fully charged. This usually is indicated by a solid, green light on the battery charger. In addition, the power gauge on the joystick or the OMNI display will indicate that there is a full charge. Even after the breaking-in period, the batteries should be fully charged before use and "topping off" the batteries with frequent charges should be avoided.
Unlike other types of batteries, wheelchair batteries should not be fully discharged before they are plugged in to re-charge. In fact, if the remaining voltage is too low in wheelchair batteries, the charger may not turn on to re-charge the batteries. This is one of the reasons why nightly charging is suggested when the power wheelchair is used daily.
The battery charger should not be plugged into a wheelchair for an extended period of time (i.e., over 2 days). Although a fully automatic charger may turn off the voltage automatically, chargers can become defective and possibly lead to dangerous conditions.
If a wheelchair is used occasionally during the week, but not daily, the batteries should be fully charged before an outing and after active use, ideally when the power gauge on the joystick or OMNI display indicates that the batteries are at about 50% (MK Battery, 2009).
Storing Wheelchair Batteries
If a wheelchair will not be used for an extended period of time (i.e., for a few days or weeks), the batteries should be fully charged and should then be disconnected from the power source by unplugging the connector between the batteries and the wheelchair. When stored, the batteries should be checked monthly and re-charged as needed.
Extremes of temperature – hot or cold – should be avoided when charging or storing the batteries. If a powered mobility device will be stored in an unheated garage over the winter, the batteries should be taken indoors to avoid the cold temperatures.
Battery Life
Good battery maintenance practices can optimize the long-term performance and longevity of the batteries. Depending upon the charging practices, a set of wheelchair batteries may last for 1 or 2 years, or longer, before requiring replacement (MK Battery, 2009).
As always, please provide your comments, questions and suggestions regarding Clinical Corner. Please email me at Sheilagh.Sherman@sunmed.com. I look forward to hearing from you!
Sheilagh Sherman, BA, BHScOT, MHM, OT Reg. (Ont.)
Clinical Education Manager
Sunrise Medical Canada
References
- MK Battery. (2009). The HME Battery Guide. Retrieved from https://www.mkbattery.com/
Note: The content of this article is not meant to be prescriptive; rather, it is meant as a general resource for clinicians to then use clinical reasoning skills to determine optimal seating and mobility solutions for individual clients. Sheilagh is unable to answer questions from members of the general public. Members of the general public are directed to their own therapists or other health care professionals to ask questions regarding seating and mobility needs.
This article is © Sunrise Medical, Inc., 2019 and cannot be copied, distributed, or otherwise reproduced in whole or in part without the express written permission of Sunrise Medical Canada.