Mount and Ventilate a Controller So It Doesn't Overheat

Why this happens

A controller's switching transistors turn some energy into heat, which flows into the aluminium case that acts as a heatsink. If the case is boxed in, wrapped, mounted against a heat source or caked in dirt, it cannot shed that heat and the controller limits power or fails early. Good mounting also keeps water and vibration away from its connectors.

What you need

Step by step

1. 1

   Disconnect the battery first

   Switch off and unplug the battery connector before touching the controller. Wait a minute, then check with a multimeter that there is no voltage at the controller's battery input, because controllers contain capacitors that can hold a charge briefly. Remove jewellery and use insulated tools. This applies to your own build or project; on a factory vehicle, do not relocate the controller, as it may void warranty.

2. 2

   Choose a location with airflow

   Pick a spot where moving air reaches the controller while riding, such as under the down tube or in an open frame bay, but away from direct tyre spray. Avoid sealed bags, foam wraps or boxes. Keep it away from the battery so their heat does not add together, and away from brake discs and the motor.

3. 3

   Orient the fins and connectors

   If the case has fins, align them with the airflow direction. Mount the controller so cables exit downwards or sideways, never upwards, so water runs off rather than into the cable glands. Plan cable lengths so they reach without strain and allow drip loops below each connector.

4. 4

   Use a solid, heat-friendly mount

   Bolt the controller to a metal plate or bracket using its own mounting holes. Metal-to-metal contact helps heat spread into the plate. Use rubber washers between the plate and the frame to reduce vibration. Do not drill into the frame near the battery or into any structural tube unless the frame maker allows it.

5. 5

   Secure and protect the cables

   Route the battery, motor and signal cables with gentle bends and secure them every 15–20 cm with cable ties, not so tight that they cut the insulation. Use grommets where cables pass edges. Put a little dielectric grease on connector seals. Make sure nothing is pulled tight when the handlebar turns or the suspension compresses.

6. 6

   Check the installation before power

   Shake the controller to confirm it is firm. Check every connector is fully latched and polarity is correct against your wiring diagram. Make sure no bare metal is exposed. Then reconnect the battery, switch on and do a stand test with the wheel lifted before riding.

7. 7

   Measure the temperature after a ride

   After a typical ride, measure the controller case with an infrared thermometer, on a piece of matt tape for accuracy. Compare it with the temperature before the change and with the ambient air. A well-mounted controller should run cooler and stay cooler on long rides. Recheck the bolts after the first week, as vibration can loosen them.

How to tell it worked

The controller is firmly bolted with fins in the airflow, cables leave downwards with drip loops, and after-ride case temperatures are lower and over-temperature cut-outs have stopped.

Questions