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7
TROUBLESHOOTING PROCEDURE 2
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FIGURE 1 - FIELD LOAD TEST
Battery Charger
Connector
Digital Voltmeter
FIELD LOAD TEST (FIGURE 1)
NOTE: The following test can also be performed through
the controller of the wheelchair along with a remote
programmer. Refer to the individual CONTROLLER
MANUAL supplied with each wheelchair.
Old batteries lose their ability to store and release power, due
to increased internal resistance. This means that as you try
to take power from the battery, some of that power is used up
in the process of passing through the battery, resulting in less
voltage at the posts. The more power drawn, the lower the
voltage available. When this lost voltage drops the output 1.0
volts under load (2.0 for a pair), replace the batteries.
Testing under load is the only way to spot this problem.
While special battery load testing equipment is available,
it is costly and difficult to transport.
Use a digital voltmeter to check battery charge level at
the charger connector. It is located on the base of the
wheelchair frame.
NOTE: READ the instructions CAREFULLY before us-
ing the digital voltmeter.
NOTE: Invacare recommends that ONLY qualified ser-
vice personnel perform this test.
1. Ensure that power is OFF.
2. Make sure battery is fully charged. An extremely
discharged battery will exhibit the same symptoms
as a bad one.
3. Place a one (1) piece of wood taller than the axle of
the drive wheels between the wheelchair and a wall,
workbench or other stationary object.
4. Remove the footrests from the wheelchair and place
the stabilizer wheels or the front of the wheelchair
against the piece of wood.
5. Place the voltmeter leads into the charger plug on the
wheelchair. Most digital voltmeters are not affected by
polarity, however, analog meters (meters with swinging
needles) can be and should be used carefully. A good
meter reading should be 25.5 to 26 VDC.
6. Have two (2) individuals (one [1] on each arm) apply
as much downward pressure as possible on the arms
of the wheelchair.
USING HYDROMETER TO CHECK
BATTERY CELLS (LEAD ACID)
(FIGURE 2)
NOTE: Perform this procedure when a digital voltmeter is
not available.
WARNING
NEVER smoke or strike a match near the
batteries. If the caps of the battery cells
are removed, NEVER look directly into
them when charging the battery.
The use of rubber gloves and safety
glasses is recommended when testing the
battery cells.
When reading a hydrometer, DO NOT allow
any liquid to come in contact with your
eyes or skin. It is a form of acid and can
cause serious burns, and in some cases,
blindness. If you do get battery acid on
you, flush the exposed areas with cool
water IMMEDIATELY. If the acid comes into
contact with eyes or causes serious burns,
get medical help IMMEDIATELY.
The battery acid can damage your
wheelchair, clothing, and household
items. Therefore, take readings cautiously
and only in designated areas.
This Procedure Includes the Following:
Field Load Test
Using Hydrometer To Check Battery Cells (Lead
Acid)
Motor Testing
Motor Brush Inspection
Electro-Mechanical Parking Brake Test
7. Turn the wheelchair ON and push the joystick forward,
trying to drive the wheelchair through the stationary
object. This puts a heavy load on the batteries as they
try to push through the stationary object. Read the
meter while the motors are straining to determine the
voltage under load.
NOTE: If the voltage drops to less than 23.5 volts from a
pair of fully charged batteries while under load, they should
be replaced regardless of the unloaded voltages.