 The
batteries most commonly used in
wheelchairs are lead-acid batteries.
This is the same general type used
in automobiles. There are, however,
a variety of specific types of lead-acid
batteries. The choice of the correct
type will contribute to more efficient,
trouble-free service, and in the
long run it will be less expensive.
Standard automobile batteries are
designed to provide the high momentary
currents needed for starting the
car's engine, rather than the lower
constant current needed to operate
a power wheelchair. Consequently,
the wheelchair battery should be
designed differently. This design
is frequently referred to as a "deep
cycle" battery. This means
its mechanical construction is such
that it will last longer and perform
better under long periods of discharge
followed by long periods of charging
that are common in wheelchair use.
There is no alternator on the power
wheelchair to constantly recharge
the battery as there is in an automobile.
The average life of a good quality
deep cycle battery in wheelchair
use is less than a year. Poor quality
batteries and those that are not
of the deep cycle type will last
an even shorter period of time.
All lead-acid batteries are constructed
of lead plates suspended in a container
filled with a mixture of sulfuric
acid and water. This fluid, called
the electrolyte, reacts chemically
with the lead plates to produce
electrical current. The deep cycle
type lead-acid battery has much
thicker lead plates, resulting in
a noticeably heavier battery. This
is one way to distinguish between
the standard automobile battery
and the deep cycle type.
Although it is widely accepted that
the deep cycle lead acid battery
is the most satisfactory choice
for most wheelchair users, even
the power wheelchair manufacturers
do not always agree on exactly which
battery is best. One manufacturer
warns against using the Sears Die
Hard battery in their chair. One
the other hand, other manufacturers
recommend that particular battery.
Completely sealed batteries are
not generally intended by their
manufacturer to be repeatedly recharged
for long periods of time. Such use
may be dangerous as a result of
the pressure of the gas (hydrogen)
being built up inside the sealed
container during the charging process.
Under extreme conditions an explosion
could result. The manufacturer of
the battery should be consulted
before a completely sealed battery
is used. When inquiring, be sure
to call the manufacturer's attention
the fact that charging will occur
daily for several hours at a time.
In addition to selecting a deep
cycle type battery, another major
consideration is the capacity of
the battery. This is measured in
ampere hours, which is determined
by the number and size of the lead
plates. The more and the larger
the plates the higher the ampere
hour rating.
Different models of wheelchairs,
different patterns of use, and different
users will require different battery
capacities. The power base type
chair designed for more outdoor
use will frequently need higher
capacity batteries. Users who travel
long distances during the day, such
as college students traveling around
large campuses, will need greater
batter capacity. Even the weight
of the user may be a factor to consider.
Most current model power wheelchairs
operate on 24 volts, which means
that they require two 12 volt batteries.
Although two batteries are required,
the capacity required for these
batteries is reduced by the higher
operating voltage. The older 12
volt power wheelchairs required
a single larger capacity battery.
Consult your wheelchair owner's
manual for the manufacturer's recommendations
regarding battery capacity.
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