Mixing ebike hub motors and water!

I can honestly say that Empowered People riders are not shy of wet weather and even the occasional deep water does not put of this hardy bunch. However this keenness to push on through the wet stuff does sometimes lead to some interesting issues with ebike motors!

I can also be personally blamed for maybe pushing my own Bafang crank motor beyond the accepted wetness level I think they were designed for, but today I want to share what damage just normal UK rain can do to wheel hub motors.

So I get the call from the Chief Simon to say that one of our riders trike needs some attention and the front motor has seized up.  it would roll forward but would lock up in reverse. Luckily I had seen this before ( on Simons own trike) so I knew what to expect.

Both hubs were the same Bafang BPM motors, and on first inspection I can see that this one would not drive at all, not a peep, and would only roll forward. any attempt to reverse would leave nice rubber skid marks on my drive.

So out with the tools and time for a strip down..

as I expected the main armature (the bit that has all the copper wire wound round it) was rusted to the outer housing that has all the strong magnets on. This is exactly the same issue we had on Simons hub. It took a bit or manual force and a liberal amount or penetrating oil to free things up and soon it was moving free again!. I took the opportunity to   the nylon gears to keep them moving. and soon the wheel was fully operational again.


What I think happens here is that over time water runs down the cable for the motor and due to capillary action makes its way into the centre of the motor where it gets flung out to the edges like a spin cycle on a washing machine. unfortunately there is nowhere for this water to go and so sits there and rusts everything in its path.

I plan to try adding some silicon to the entry for the cable to try to keep the wather out in the first place, but one thing I do suspect is that the plastic cover for where the cable goes into the motor is actually holding water and helping guide it into the motor, so it may be a good idea to try removing that or at least adding a small hole in it to let that drain.

But remember guys if your e bike does get wet, try your best to get it dried out as soon as possible, I know this trike has covered many miles without issue in wet and dry conditions so it has taken a while for the water to build up.

oh and if you think this one looked bad, this is what Simon’s motor looked like after an unfortunate dunking…



Hi, I am one of the trustees of Empowered people. As well as looking after this website, I am also an ebike builder, modifier, hacker, and general bike mechanic. I have been involved with the Charity since 2015 and participate in as many rides as I can with my wife Catherine on the 'Bike Train' if you look around the website you are sure to find me in the background somewhere.

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