2.2.4 Battery protection
2.2.4.1 Thermal circuit breakers
To protect the batteries and the system cables from external short circuits, a thermal
circuit breaker or fuse must be installed between the batteries and the rest of the
system - as close as possible to the batteries. If the two batteries are permanently
wired together in a single battery box, the best position for the circuit breaker is
between the two batteries. If the batteries are separated in individual battery boxes,
each battery requires its own circuit breaker.
The circuit breaker or fuse must be of the slow acting type. The rating of the circuit
breaker must be appropriate for the power requirement, including the total weight of
the chair, the battery capacity and the wiring.
GBK60348
: Issue 1 – October 2007
16
2.2.4.2 Battery Saver
If the battery Voltage falls below 21V, the DX System reduces the performance of the
powerchair. This
• protects the battery
• gives the powerchair a longer range before the battery is completely empty
• gives the user a physical warning that the battery is almost empty before
the battery is damaged.
2.2.4.3 High Voltage Rollback
High Voltage Rollback is a battery protection feature that is especially useful for users
who have to drive downhill often.
When a powerchair drives downhill, the Power Module sends the generated motor
current to the battery. However, if the battery is fully charged already, it can not
accept the generated current anymore. This causes the battery voltage to become
too high, which can cause damage to the battery or the controller.
High Voltage Rollback gradually decreases the speed of the powerchair until the
battery can accept more current. The deceleration of the powerchair gives a timely
physical warning to the user to take corrective action, like turning on the lights or
slowing down.
High Voltage Rollback can be enabled with the Wizard (see
4.3.4.6).
Single Battery Box
Thermal Circuit
Breake
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