Batteries are the heart of every power wheelchair and scooter. They
"pump" the electricity to the motors, and the sophisticated
electronics used by todays power chairs and scooters closely
measure their output voltage. If it drops before a certain level, the
electronics shut down to prevent damage.
Depending on the electronics, you may or may not get an error message
when this happens. But over 90% of the service calls we get involving
electronic problems are nothing more than either wrong, defective,
un(der)charged, or "used up" batteries. Most wheelchair manufacturers
will not even talk to the service technician to troubleshoot a problem
until s/he determines that the batteries are good. Some insist that
new batteries be installed (they can be removed after the chair or
scooter is running correctly and it is determined the old batteries are
not to blame) whenever there is an electrical problem to see if the
problem goes away or changes.
Most modern power chairs and scooters have (2) 12 volt batteries wired
in series to create a 24 volt system. The wiring may be obvious (the
positive terminal of one battery connected to the negative of the
other), or it may be done internally in the equipment's electronics
(usually the case for scooters and not rare in some power chairs). To
the batteries, it is like having one large battery- and because of
that if one battery is bad (or even weak), it will bring the other
battery "down". It is very important to always replace the 2 batteries
as a set at the same time.RANGE OF WHEELCHAIRS AND SCOOTERS BETWEEN CHARGES AND BATTERY REPLACEMENT
The manufacturer of the equipment will advertise a range that the
wheelchair or scooter can go between charges. Usually they will word
it as: "between ## and ## miles between charges". My advice is to take
the lower of the 2 numbers and make that the maximum range.
Further, the range is qualified to a (usually) 170 pound user on
level ground at 70` temperature. This is a constant in the industry.
And the manufacturer will (obviously) use good quality batteries when
computing the range.
As the batteries age, that range will decrease. Given enough time, the range
will become essentially zero miles. Usually after one year, the range has
decreased enough that the same "average" user can't go a full day without
recharging. Obviously a person who is only going several hundred yards a day
indoors will have a greater range than an active user traveling great distances
outdoors (example: a college student "on campus" going between classes).
Several ultra-small scooters and wheelchairs have come on the market. These
tout their light weight as their selling point. Understand that most of these
have very small batteries. These batteries will have both a much shorter range
between charges AND a much shorter life between replacement! A general
rule is that the shorter the advertised range, the shorter the life of the
battery before replacement.
WHEELCHAIR/SCOOTER BATTERIES AND "MEMORY"
There is no "memory effect" in wheelchair batteries. If you drive the
equipment that day, charge it that night. The batteries will not develop
a memory, and if you were provided with poor quality or "automotive"
batteries, doing so may buy you a little longer life.
AUTOMOTIVE BATTERIES IN WHEELCHAIRS AND SCOOTERS
Quite simply, they do not work. Automotive batteries are designed to
put a large amount of power out in a very short amount of time. They
are also designed to deal with very high extremes of temperature under
the hood of a car (from below zero on a cold winter night up north
with the wind blowing, to over 250 degrees under the hood of a car
stopped on I95 in a rush hour traffic jam). An automotive battery
does its job for maybe a minute or so while the starter is engaged.
Then the automobile's charging system "kicks in" when the engine is
running and recharges the battery. The battery must also be designed
to withstand the "pressure" of the charging system against it for many
hours of driving while the battery is fully charged. Because the car
battery is really only used for a minute or so at a time (the
electrical system may "borrow" from the battery at a stop light or in
stuck traffic if a lot of accessories are running, but this is minimal
and non-existent when the car is moving), it can last a few years or
Batteries for wheelchairs and scooters have the opposite problem. The
temperature requirements and output (compared to an automobile
battery) are minimal, but the battery must go from fully charged (in
the morning right off the charger) and power the wheelchair/scooter
all day without recharging- and without going slower as the charge
diminishes (within reason). The chair is then put on a charger and
the battery is recharged slowly, usually over night. The term for a
battery going from fully charged to discharged to fully charged again
is a "cycle", and because the battery is going to discharge quite a
bit, the term for a battery that can do this over and over again is
"deep cycle battery". Automobile batteries are "high output
batteries", wheelchair batteries are "deep cycle batteries". Most
deep cycle batteries are good for 350 to 500 "cycles"- figure a year
of usage. Your mileage may vary.
To compound the problem, a lot of places that sell batteries simply
don't understand this concept. Others simply don't care. And it is
impossible to tell a deep cycle battery from an automotive battery by
looking at it (except for the label, which many times is put on by the
battery supplier at the time of sale). As a dealer, I have had
battery suppliers deliver to me automotive batteries with deep cycle
labels on them. We find out they are the wrong batteries a month or
so later when they start to fail (and the customer is very angry at
that time). The battery company may provide you with a replacement
warranty- usually pro-rated, but even with "full free replacement",
you will not be reimbursed for your inconvenience, lack of use of the
equipment while waiting for replacement batteries, or any service
call you encounter trying to determine that the batteries are
defective/non-deep cycle (assumes you didn't get your batteries from
the company who is now diagnosing the electrical problem). Many
battery companies will insist the batteries "test" fine when in fact
they cannot hold a charge for a full day (because they are "starting"
vs "deep cycle" batteries.
Automobile and deep cycle batteries come in the exact same sizes (see
size section). This just compounds the problem. And scooters users
(that generally use a smaller battery) now have to contend with 2
additional problems: the "garden tractor" starting battery (wet) and
the "emergency light" battery (gel- see "wet vs gel" section). These
aren't generally considered automotive batteries (due to their size),
but they are not deep cycle either. But the size is the same as the
majority of scooter batteries (U-1). Some companies selling scooter
batteries mail order have shipped emergency lighting batteries as deep
WET VS "GEL" (Sealed Lead Acid)
Batteries appropriate for wheelchairs and scooters come in different
sizes and in the past came in two "types": liquid or sealed lead acid.
Sealed lead acid batteries can be manufactured with a gel inside to hold
the acid in place (it's mixed with the gel), or they may have fiberglass
matting between the plates to hold the acid in place. Because gel
batteries were the first kinds of sealed lead acid batteries, many people,
including dealers, call all non-spillable batteries "gel cells", and
the ones with the fiberglass matting "sealed lead acid". I am using
"sealed lead acid" (the correct term) to encompass all non-spillable
batteries as their characteristics to the end user, care, and charging
procedures are identical. Today, all wheelchairs and scooters should if
at all possible have the non-spillable sealed lead acid batteries
installed instead of wet batteries. The damage cause by spilled acid
is expensive, and the "gassing" of wet batteries causes both damage to
the wiring/electronics/frame of the chair and poses a possible (albiet
very slight) chance of explosion. Battery connections loosen when
corrosion is present- causing more (expensive) service calls.
Sealed lead acid batteries do cost more (more expensive to produce),
and in the past did not last nearly as long as properly maintained
liquid deep cycle batteries, and do require a special battery charger.
As their output and range is less than sealed lead acid batteries, some
mobility manufacturers did not recommend them for their chairs.
Manufacturers now recognize the benefits of sealed lead acid
batteries and I don't know of any wheelchair/scooter manufacturer now
selling in the USA that is not providing the "correct" charger as standard
equipment. One manufacturer (Invacare) has even started putting larger
battery boxes on some of their power chairs to compensate for the lower
range/capacity of sealed lead acid batteries. Given that the life of
a sealed lead acid battery now is almost as long as a wet battery, the
advantages of using a nonspillable battery is certainly worth the
difference in cost. Particularly if the wet battery ever spills...
Note: it is becoming more difficult to find good quality wet
deep cycle batteries in the smaller sizes (U1 and 22NF). With the
exception of the product of a specialty wheelchair battery company (MK
Batteries), the vast majority of wet "deep cycle" batteries I have seen in
the past 2 years in these sizes have not been deep cycle but rather automotive.
I highly recommend MK Batteries (click to open a window to their site-
this is the brand I sell) as they are the only battery company that I am aware
of that markets their batteries for use specifically in wheelchairs.
They have a staff that works with the wheelchair and scooter manufacturers.
Getting a MK battery means getting a wheelchair battery!SIZE:
The size of the batteries is important. Generally the manufacturer
specifies one size that is appropriate for that particular chair or
scooter- and that is the size that fits the battery box. As the
battery size gets larger, the price goes up, so some customers (and
dealers) are inclined to put a smaller battery in to save $$$. This
usually should not be done. The larger battery will have slightly
more electrical output, and greater range before becoming so
discharged that it ceases to work. Generally, the lower price paid
for the smaller battery is not compensated for in the life of the
battery. It is cheaper to get the correct size because it will last
longer before having to be replaced (and may save the electronics from
failing due to low output).
BATTERY CHARGING AND CARE:
Sealed Lead Acid
Sealed lead acid batteries if properly installed should require no
maintenance. Never remove the caps, or try to add water. No corrosion
should ever be present unless the battery is beyond its service life.
While the connections should remain tight for the service life of the battery,
do check them and all other connections from time to time to make sure they are
tight and in good condition.
Make sure the connections and battery case are clean, tight, and free
of any corrosion. Make sure that all connections are dry and tight-
not just on the batteries, but everywhere on the chair/scooter. Due to
corrosion, connections will loosen and connectors will deteriorate.
Check the water on wet batteries every couple of months.
Any water above the metal plates is "bonus". Don't go crazy topping
off. This leads to over filling. As long as the plates are covered,
and when you check the top of the plates aren't "dry", you are fine.
An automatic charger should automatically shut off so that the only
water loss is due to evaporation. If you are using a "clock" type
charger, it may be necessary to check the water level more often and
to adjust the amount of time every day that the batteries are charged.
Check and add the water when the battery is "warm" from just being
charged (ie: first thing in the AM if the battery was charged that
night). That way it won't be overflowing by the water expanding when
the battery warms up during its charge (normal). If the batteries
are "drinking water like crazy" (and not filling over into the battery
box) it means that they are "used up" and must be replaced. Failure
to do so will not just strand you someplace, the gases escaping will
corrode everything they touch and possibly cause an explosion which
means: Do not smoke while checking the water in the batteries. Do not
use a match or lighter for light to see the water level.
Distilled water is preferred in areas with high concentration of iron
or other minerals in the water.
CHARGING (all battery types)
Batteries should be charged every night if the chair is used for any
distance that day. Some people find it more convenient to only charge
a couple of times a week. This will not damage good quality
batteries, but the user does run the risk of "running out" of power-
particularly as the batteries age as their "range'" decreases. Unlike
batteries in some cellular phones or camcorders, wheelchair batteries
will not take a "memory" by charging before the batteries "run down".
This should not be a consideration when deciding how often to charge.
The best rule: "If you drive it that day, charge it that night".
Another reason to charge daily is that it gives the user a greater safety
margin if for any reason the chair or scooter cannot be charged. Example:
power failure or charger failure. By always having "full" batteries, this
buys you extra days when the batteries cannot be full (like always driving
your car with a full tank of gasoline).
Generally an overnight charge will be all you will need.
I advise against leaving any charger on more than 24 hours, and while
I would not go rushing home from the store if its been that long, I
would make a phone call to have it disconnected if you are
away from the chair for an extended period of time.
If the charger is not shutting off (reading "full") after 12 hours, chances are
the battery is beyond its normal service life and should be replaced.
Or the charger is defective.
Never ever use an "automotive" charger on a sealed lead acid battery.
Remember, many (most?) chargers are 24 volt "out". Any kind of battery
will be damaged and/or will damage the charger if the wrong
battery/charger "combination" is used. And many chargers have
the same size/style chair "plug", but are wired differently.
Never use a charger that was not provided with your chair/scooter unless
a technician determines that it truly is computable.
Just because a charger is automatic, doesn't make it OK for Sealed
Lead Acid batteries (gels). The "finishing voltage" is higher in a
wet battery, particularly if the amperage of the charger is over 5
amps. It is that finishing voltage that kills a gel battery- sometimes
in just 5 "cycles" and a gel mode's finishing voltage is lower.
I have found that gel-only chargers do just fine with wet batteries,
but they take longer to recharge as they are 3 or 5 amps (instead of
8 or 10). A "dual mode" charger has the best of both worlds: high
amperage and the correct finishing voltage. They are quite expensive,
though. Lately, a new breed of "smart" chargers has come along. Some
of these are quite reasonably priced (compared to dual-mode), and while
most don't have the high output of the dual-mode chargers, they are so
efficient that they charge even larger batteries quite quickly (still