4qd VTX-40 Instruction Manual - Page 7

Browse online or download pdf Instruction Manual for Controller 4qd VTX-40. 4qd VTX-40 16 pages.

Print Page

Power Connections

Battery wiring

Battery connections to the controller are shown in the

diagram opposite. Use only good quality battery

connectors: the controller feeds current back into the

battery during braking and if a battery connector falls

off when braking this regenerated current can pump

up the voltage on the dud battery connection.

Although the controller is protected against damage

from this, it is not advised. The same will happen if a

fuse or circuit breaker opens during braking.

Note that, if the battery is disconnected for a minute

of more, when the battery is re-connected, it is

normal for there to be a noticeable spark as the main

capacitors charge.

Polarity

Take great care: THE CONTROLLER IS NOT

POLARITY PROTECTED: BATTERY

REVERSAL WILL INSTANTLY DESTROY THE

CONTROLLER!

This will not be covered by the guarantee!

In practise a suitable fuse (opposite page) gives quite

effective protection. However a more positive

protection against reversed battery can be done by

wiring a suitable relay (one normally open contact) in

the positive battery lead. One end of the coil connects

to battery -ve and the other to pin B of the input

connector which is also connected to the ignition

switch. A resistor must be connected across the

contacts as shown. When the ignition is off, there is

no voltage on the relay coil and the relay contacts are

open. The VTX's main capacitor charges through the

470 ohm resistor.

If the battery is reversed the VTX's MOSFETs short

+24v switched by ign switch

Battery -

VTX series instructions

Battery +

Relay

470 ohm

2 watt

+ to controller

out the capacitor, so no voltage is present and the 470

ohm resistor limits the current to a safe value. When

the ignition switch is closed the relay coil is

connected across the capacitor: if there is voltage

(battery correct) the relay operates and applies full

power.

Wire size.

Use heavy duty wire for the battery and

make them as short as possible. This also applies to

the battery linking wire on 24v systems. 4mm

(12awg) wire is 'officially' rated to handle 41 amps

continuously. At 100 amps it gets too hot to touch

within about 60 seconds, so it is fairly well matched

to the controller. You may prefer to use 6.0mm²

(10awg) wire for the 75 amp version. Thicker wire

will cause no problems, so use the thickest you have.

Use of wire that is too long (and/or too thin) will

cause loss of power, but more importantly the

decoupling capacitor (see 'features' diagram above)

will heat up. Heat will shorten the operating life of

capacitors.

Crimp Contacts

It is VERY IMPORTANT that you use fully insulated

crimps: the power connections are close to the board.

Uninsulated crimps may short out and destroy the

controller. Best of all use 'F type' crimps with vinyl

covers shown in the drawing.

4QD can supply these pre-

crimped - they require a special

crimp tool.

Also be aware that the main

capacitor can store charge for a

long time (several minutes) so

the potential for damage is there

after the battery has been

connected.

Page 7