Rear hub runs, but hard to spin manual/electric

[att]

Greetings everyone, I just joined the forum and already starting a question. Hope I’m not to quick asking and I’ll try to keep this short and concise.

I have an old ebike, 36V lead battery, rear hub motor. The wheel doesn’t freewheel at all, it’s hard to move it by hand.
Got it second hand with it’s charger, but no documentation and it has no labels. Perfect Chinese noname I guess.

It used to work, about a year ago, even though I never used it much. Didn’t use it for a lot of time and just decided to start using it a few days ago. Charged the battery and tested: the wheel spins, but slowly. The bike can carry me around, but slowly. I lifted the rear wheel off the ground and saw it’s very hard to spin, with or without the motor cables connected, with our without the battery connected. There’s no difference.

I removed the wheel from the bike and removed the drum brake completely. No difference. The axle is impossible to spin by hand when the wheel is off the bike. I held the axle with pliers and then I can spin the wheel, just as hard to spin as when it’s installed on the bike.

I can ride the bike for 50-100 m in all electric mode, but the bike is very slow compared to what it was, maybe reaching 7-10km/h on flat surface. I don’t want to force it, maybe it’s still repairable.

I measured a few things: the battery voltage around 37-38V when disconnected, drops to 36V when spinning the wheel off the ground. Drops to 33-34V when I force the throttle and the wheel is rubbing the ground. The battery is a bit old, but that’s not the issue for sure.

I have 3 thick wires coming out of the motor. I measured them with the motor unplugged from the controller and they show 0.8 ohm with a Fluke meter. When I turn the wheel by hand there’s some voltage generated between the wires, checked on each pair of two. If I short the 3 motor wires together, the wheel is even harder to spin.
I measured the voltage between phases and saw it raises to aprox 18V between wires with the throttle on max and the wheel spinning off the ground.

I am not sure how to open the motor. I removed the screws holding the lid, but the cover won’t open.
I’m no professional in the field, but I did lots of repairs on normal bikes.
On a normal bike I would diagnose this as being bad bearings, or the bearings being too tightened by the axle nuts. However, this bike ran well before and nobody dismantled it to play with the bearings. Can't tell for sure though if anyone knocked it down and raised it back up, as it's been stored in a share bike room. There’s no weird disintegrated bearing sound.

Maybe someone can give some advice? I’d like to start using the bike for commuting to work and really don’t fancy buying a new one.
Thanks for any tip!

 

[Nealh]

To open it one has to remove the inner axle nut on the other side then the lid should come off.
If the motor isn't turning/freewheeling very well it could be down to rust or phase wires shorted, check the cable as it enters the axle and see if the cable is split or any bare wires. The clutch mechanism may be stuck .

 

[att]

Thanks for the tip, Nealh, it was indeed rust inside the motor. Lots of rust. Amazing, as there was nothing visible outside. After cleaning with a brush and a bit of greasing, the bike works. It was a pain to open up, but worth it. I bought 100 pieces 18650 cells and built them into a 10s10p pack and now I've got a >50km electric ride. Best Christmas gift I made myself.
My Diesel can stay home now, my work commute just became electric!

Big thank you to all folks describing here how they built their battery packs.

 

[Nealh]

Moisture has two possible routes to the inside of the hub.
One is via the motor cable, if it is orientated in the D/O's incorrectly moisture can track down the cable and then inside. So the cable entry must always enter on the under side where it can form a drip loop also one can syringe some white w/p grease in the entry as well.
The other possible entry point is via the disc rotor mount holes (there are six), some hubs the holes are blind so not an issue. On others they continue in to the planetary/sun gear void and can let in water/moisture.

One doesn't have to do it regularly but for a commute bike that may see a lot of wet weather riding it is worth opening the hub every year or two for a brief maintenance check.

 

[miwklrini]

Greetings everyone, I just joined the forum and already starting a question. Hope I’m not to quick asking and I’ll try to keep this short and concise.

I have an old ebike, 36V lead battery, rear hub motor. The wheel doesn’t freewheel at all, it’s hard to move it by hand.
Got it second hand with it’s charger, but no documentation and it has no labels. Perfect Chinese noname I guess.

It used to work, about a year ago, even though I never used it much. Didn’t use it for a lot of time and just decided to start using it a few days ago. Charged the battery and tested: the wheel spins, but slowly. The bike can carry me around, but slowly. I lifted the rear wheel off the ground and saw it’s very hard to spin, with or without the motor cables connected, with our without the battery connected. There’s no difference.

I removed the wheel from the bike and removed the drum brake completely. No difference. The axle is impossible to spin by hand when the wheel is off the bike. I held the axle with pliers and then I can spin the wheel, just as hard to spin as when it’s installed on the bike.

I can ride the bike for 50-100 m in all electric mode, but the bike is very slow compared to what it was, maybe reaching 7-10km/h on flat surface. I don’t want to force it, maybe it’s still repairable.

I measured a few things: the battery voltage around 37-38V when disconnected, drops to 36V when spinning the wheel off the ground. Drops to 33-34V when I force the throttle and the wheel is rubbing the ground. The battery is a bit old, but that’s not the issue for sure.

I have 3 thick wires coming out of the motor. I measured them with the motor unplugged from the controller and they show 0.8 ohm with a Fluke meter. When I turn the wheel by hand there’s some voltage generated between the wires, checked on each pair of two. If I short the 3 motor wires together, the wheel is even harder to spin.
I measured the voltage between phases and saw it raises to aprox 18V between wires with the throttle on max and the wheel spinning off the ground.

I am not sure how to open the motor. I removed the screws holding the lid, but the cover won’t open.
I’m no professional in the field, but I did lots of repairs on normal bikes.
On a normal bike I would diagnose this as being bad bearings, or the bearings being too tightened by the axle nuts. However, this bike ran well before and nobody dismantled it to play with the bearings. Can't tell for sure though if anyone knocked it down and raised it back up, as it's been stored in a share bike room. There’s no weird disintegrated bearing sound.

Maybe someone can give some advice? I’d like to start using the bike for commuting to work and really don’t fancy buying a new one.
Thanks for any tip!

Maybe the brake handle was pushed. An X5 turns smoothly with a short unlike the newer types that are clearly notched in the turning resistance and easier to identify. A phase short isn't going to go away like that, and a phase short will get noticeably harder to turn the faster you try to turn it, not easier. Messing with motor wires and popping covers off unnecessarily is asking for trouble AFAIC.

I'd suggest first disconnecting from the controller, and short a couple of phases together to see if it feels the same. Inspect the wiring outside the motor for damage, and feel your phase wires for heat immediately after your most demanding type of riding. Wires don't just break by themselves, so unless they're damaged or melted it doesn't seem likely. A phase wire short certainly isn't going to fix itself, and then run properly, and not get immediately worse, so it seems unlikely, not impossible, but unlikely.

Have you had the motor opened before? Did you buy it new or used? Do you ride in the rain, and if so, do you have a proper drip loop? I've seen working motors that I bought used with so much corrosion from water getting in that they were nearly locked up upon arrival down here, and I've heard of working motors with lots of water in them. Without a drip loop, water follows the wires right into the motor. I can easily see that causing your symptoms.