Section 13-Current Rollback; What Is Current Rollback; What Increases The Likelihood Of Current Rollback; Weight - Invacare MK5 EX Service Manual

SECTION 13—CURRENT ROLLBACK
SECTION 13—CURRENT ROLLBACK

What Is Current Rollback?

Current flows from the batteries, through the controller into the motors. In simple terms,
current relates to power (Amps is a measure of current). As speed, load, rolling resistance
and terrain angle increases so does the amount of current flowing through the system.
Current generates heat. If the heat is excessive for too long, it can lead to component
failure. To protect the system, all MK5 controllers have been programmed to limit the
amount of current drawn through the system to prevent damage to the circuitry and
motors. This feature is called Current Rollback.
If the internal temperature of the controller reaches the current rollback setting, the
controller will automatically reduce the output which will cause the wheelchair to slow
down or stop, depending upon the load and operating terrain. The controller has an
internal timer that keeps the operating system at this reduced output until the system has
had ample time to cool down. Once it counts down, full power output is restored to the
system.

What Increases the Likelihood of Current Rollback?

• Weight

• Rolling Resistance

• Terrain Angle

• Speed

Weight
Weight includes the weight of the user, all accessories mounted to the wheelchair and any
additional weight accompanying the user such as back packs etc. (It takes more energy to
move a wheelchair that is equipped with a power tilt/recline seating system and a
ventilator than a wheelchair that is equipped with a standard seat only).
Rolling Resistance
The surface that the wheelchair is operating on makes a difference to how hard the
wheelchair has to work. Sand or deep grass offers more rolling resistance than pavement.
Terrain Angle
Inclines require the system to work harder as you fight gravity. Ramps are obvious but
the land terrain (slopes, hills) are not as obvious, but play a part in current rollback.
Speed
A system at 100% forward speed requires more power than one programmed at 75%.
Combine high-speed settings with factors described above and you increase the
likelihood of going into current rollback.
77 ™ ™ ™ ™
Part No 1114808 MK EX and MK TT-EX Electronics
5 5