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4QD series controller instructions.
The drawing shows the base board with the control
(top) board removed. The adjustment is to the left of
the 14 way connector.
Typical voltages for various settings are shown
below. Note that these figures are not guaranteed: if
you need accurate setting, measure it!
Position
U/V
For Battery
Fully clockwise
40v
3 o'clock
37v
48v
centre
27v
36v
9 o'clock
17v
24v
Fully anticlockwise
14v
Battery discharge protection
If a battery is discharged too much it can be
permanently damaged. Most manufacturers suggest
80% discharge corresponding to a voltage of about
10.5v for each 12v of battery. In most applications
the owner is quite capable of not abusing batteries,
but when you are re-selling a machine this feature
can seem to be attractive as you may expect it to
save expensive warranty claims on the batteries!
Unfortunately life is not that simple: as a battery
ages it effectively shrinks so eventually it will not
perform the required duty. Fitting discharge
protection will hasten this point - so may in fact
cause more complaints than it cures!
How It works
The protection cuts back the performance of the
controller as the battery discharge level is reached.
This enhances the behaviour that would be expected
with a flat battery. However the controller can't tell
the difference between a flat battery and poor battery
connection or an over-length battery wire.
Battery Contactor
A contactor should be fitted in the battery line as
shown. This provides an emergency power
disconnect so is a vital, safety feature. It also gives
protection against reversing the batteries.
The relay coil is fed from the ignition switch
connector. A 470ohm, 2 watt resistor must be fitted
across the relay contact to pre-charge the main
capacitor in the controller.
When the battery is connected up, current flows
through the resistor to charge up the controller’s
capacitors. When the ignition is switched on, the
capacitors are connected across the relay coil which
pulls in, shorting out the resistor. If the battery is
reversed the MOSFETs in the controller short out the
capacitors so they do not charge up and the relay
cannot operate. The fault current is limited by the
resistor to a safe value.
¶ Circuit breaker or fuse.
Use of a circuit breaker or fuse is optional: in
practise circuit breakers and fuses aren’t fast enough
to protect semiconductors, so may not offer the
controller full protection.
However a circuit breaker can also act as a power
switch to disconnect the battery. It is also possible
that a suitably small fuse or breaker in the battery
could protect against reversed battery, but this will
depend on the size of the battery wiring and the
response of the breaker.
If fitting a breaker in the battery this should not be
opened while the motor is running: as the controller
brakes, it feeds energy back into the battery. If this is
disconnected, the controller can generate a very high
voltage as it tries, in vain, to regenerate the braking
energy.
undervoltage
minmax
Ignition switch
Relay
Diode
1N4148
470R 2w resistor
From b
+ to controller
D
C
B
A
