Welcome Rad Power Bike owners!

Buying a Rad Power Bike? Support the forum and use my affiliate link:

Be sure to sign up for a free account to see posted images.

Note: To help support to ongoing costs of running
the site we use Amazon affiliate links.

Main Menu

Rad Mini intermittent motor power loss.

Started by BarryR, April 27, 2024, 03:24:29 PM

Previous topic - Next topic Rad E-Bike April 2024 Promotion


Every once in a while my rad mini motor loses power. When applying throttle the motor weakly moves a short distance then stops. If I rotate the rear wheel backwards a little and re-apply throttle the motor does the same thing. On the 2 previous occurrences of this issue it fixed itself but the latest occurrence did not fix itself. After a few days of unsuccessful diagnosis I accidentally bumped the cables under the pedal crank and suddenly the motor started working again.

I inspected the cables and connectors but found no damage and all the connectors were fully seated. I wiggled the cables and connectors, I took the bike for a test ride but the bike worked perfectly again. I suspect that maybe the cable or the connector between the battery cradle and the controller has a problem but until I can recreate the problem I can't be sure of which cable is causing the problem.

What is strange is that when this happens there is no power loss to the rest of the bike. The Display remains on, the lights work, the brake light works when squeezing the brake handles and when applying throttle the display shows wattage being applied to the motor which in itself is kind of strange because the motor isn't running.

Has anyone seen these the same or similar symptoms and figured out what is causing this?


you may have burned the wiring on the cradle where the battery plugs in.  It happened to me.  I tend to use throttle a lot and I have an upgraded controller so I send lots of juice through it. 

I replaced the connectors on both the battery and the cradle. 

Is your battery difficult to remove?  If so then it is a sure sign that you have burned the wiring.  Rads wiring is smaller than it should be.


No the battery is easy to remove and during my diagnosis I did check the connector for damage of any kind but it's all fine.

John Rose

Quote from: BarryR on April 27, 2024, 03:24:29 PM... and when applying throttle the display shows wattage being applied to the motor which in itself is kind of strange because the motor isn't running. ...
That is the strangest thing.
Otherwise, I would've suggested checking out the adjustment of the motor cut-off switch built into the right brake lever. It's in the vicinity of the throttle, and if the cut-off switch is just on the threshold of switching off, it may be jostled by twisting the throttle.

A voltage can be applied to a motor, but you can't really "apply wattage" to the motor.
Wattage is a measure of Power, and Power = Voltage x Current

For a watt meter to work, some current has to be going through something and then multiplied by the voltage to get power in watts, unlike with a volt meter which can measure voltage across an open circuit.

In this case, it may be that the current is passing through something other than the motor, but which the controller assumes is the motor. Some kind of short circuit in the wiring perhaps, or some path through the motor that does not result in it turning.

RadMini ST 2 / RadExpand 5


Any other component on the bike would let out the magic smoke if it pulled that much power. I suspect that to save on extra components in the controller the wattage displayed is just software showing what the controller is programmed to output rather than the actual current draw of the motor.

In most of the posts that I have read about sudden power loss on E-Bikes the whole bike shuts down so the owners of those bikes never get to see what I am seeing.


Radmini 4 intermittent power loss. I solved by replacing the 4 into 1 harness from controller to handlebar. It was faulty at the 1 to 4 join.