Check cooling of the motor and controller

Home mechanic (basic tools) · Time: 20 to 40 min (estimate) (estimate)

Electric motors and controllers make heat, most of all on long, slow climbs with a heavy load. Hub motors can build heat faster than they can lose it on steep, slow climbs (Upway). When they get too hot, the controller reduces power or cuts out to protect itself, then recovers after cooling. Most commuter bikes are air-cooled: heat leaves through the motor shell, fins and the controller case. Some larger bikes use liquid cooling; follow the manual for those. This job removes the things that trap heat or add load.

Safety

• Let the motor and controller cool before touching them. They can burn skin after a climb.
• Do not use a pressure washer on the motor, controller, connectors or battery. Water can be forced past the seals.
• Do not cut holes in covers or remove heat shields to "improve cooling". This lets water in.

You need

• A soft brush and a spray bottle of clean water.
• A tyre pressure gauge.

Steps

1. Let the bike cool fully. Switch off and remove the key.
2. Find the controller (manual or dealer). Check nothing covers it: bags, sacks, extra panels, mud packed around it. Upway names blocked air flow around the controller or battery as a common cause.
3. Brush dry mud and dust off the motor shell, any cooling fins and the controller case. Wipe with a damp cloth if needed.
4. Check tyre pressures: Check tyre pressure. A soft tyre makes the motor work harder.
5. Spin the wheel: check the brake is not dragging, Check for brake drag. On a chain or belt drive, check it is not too tight: Check and adjust chain slack.
6. Check the load: is the bike carrying more than the manual allows? Passengers plus cargo on steep hills is the classic heat case.
7. On a liquid-cooled bike, check coolant level and the pump as the manual describes. This is often workshop work.
8. Ride your usual route. If the power drops on a climb, stop in the shade, let it cool, and note how long until power returns.
9. Change how you ride on long climbs: use the lower power or "eco" mode if your bike has one, and avoid long full-throttle climbs at low speed.

Check your work

• Motor and controller warm after a ride, not too hot to touch comfortably (Upway: "warm is normal").
• No power drop on your normal route.

If it did not fix the problem

• Motor still overheats: Diagnose a motor fault.
• Controller still overheats: Diagnose a controller fault.
• Battery hot: do not charge until it cools (Ather). If it is very hot, hissing or smells: Battery pack is hot, hissing or smells.