Is anyone familiar with the "Popstar750W" E-bike?

[elecdonia]

A friend of mine recently acquired 2 of this model:  "Popstar 750W" E-bike. One runs. the other doesn't.

I'm a newbie when it comes to to E-bike technology. But I have years and years of electronic design/debugging/repair experience.
Now I want to learn about E-bikes. We live in a major midwestern state university town (45,000 students). Foreign college students routinely abandon items like E bikes when they graduate and leave town. That's where these came from.

Link to the brand:    https://scootstar.net/index.html

Battery packs are 48V 13Ah.

Motor controller:
    Rated 48V, 25A max, 12A nominal, 750W
    Under voltage protect: 39V +/-1V
    Drawing # LD-BGL-157-CG-6

Is this a decent quality E-bike?
This model is sold by dealers (not Amazon). Typical selling price is ~ USD $2k. So I don't think these are "cheapie" models.

[mzzj]

Not familiar with this particular model but these chinese bikes built around Bafang rear motor are dime in a dozen. Decent battery capacity and motor, othervise generic lowest-cost chinese junk.

If controller powers up start debugging from brake lever switches and throttle handle on/off switch. If no power start from battery and motor controller and their connectors.
Sorting out the problem should be pretty easy as you have two bikes to swap parts.   

Controller models and connectors are bit different for every make, model and yearly quarter but you should be able to re-wire about any Bafang 750W geared rear hub compatible motor controller to your bike if needed. 

[elecdonia]

It turns out that our Popstar E-bike which won’t run has a faulty handlebar display unit.

One wire had pulled out of the tightly sealed module. A replacement display module is on order. I don’t think the faulty display module is repairable. It is fully potted with cured silicone sealant.

Has anyone ever been able to tear down an E-bike handlebar display module without destroying it in the process?

[elecdonia]

Chinese bikes built around Bafang rear motor are dime in a dozen. Decent battery capacity and motor, othervise generic lowest-cost chinese junk.

I’m seeing a lot of YouTube videos and other reports stating that Bafang rear hubs have a problem with water ingress. This causes rust & corrosion which often leads to eventual failure of the clutch & planetary gear assembly.

It’s probably best to protect these bikes from rain when storing them.

Has anyone come up with a good fix for this water issue?
Could a plastic shield or rear fender extension work?

[mzzj]

I’m seeing a lot of YouTube videos and other reports stating that Bafang rear hubs have a problem with water ingress. This causes rust & corrosion which often leads to eventual failure of the clutch & planetary gear assembly.

It’s probably best to protect these bikes from rain when storing them.

Has anyone come up with a good fix for this water issue?
Could a plastic shield or rear fender extension work?

Add 50 to 100 ml of ATF oil inside the motor. (I did this in attempt to improve cooling when supercharging the motor with bigger controller)
Oil will splash and spray around and keep everything well lubricated and corrosion free.

You might need to improve the shaft sealing on brake disk side as some oil tends to seep out and lubricate your brake disk.   
On chain sprocket side small oil leaks would be just beneficial.

[elecdonia]

Got a different handlebar LCD display unit. Slightly different models:
     New: S900
     Original: C961

The new S900 display only shows error messages. However the bike itself will operate with it. The issue is that nothing useful is getting displayed.
Is the S900 incompatible with the controller and/or hub motor on this bike?
Or does it only need proper programming & configuration settings?

Handlebar power button and + - control buttons are hardwired to these LCD display units.

I’ll post photos of old vs. replacement LCD displays as soon as I visit the place where the bike is.

Just to clarify, we have 2 of same model Popstar bikes, but now we have 3 LCD displays: The broken original LCD display (C961), a fully functional original display (C961), and the new display (S900) which only shows error messages.

Both bikes operate with the working original LCD display (C961). All features function normally.

Neither bike works with faulty original display (C961). Handlebar power button doesn’t work. Bike won’t switch on.

New display (S900) gives same error message in either bike. Both bikes will operate with it: Hub motor can be controlled by pedaling or by thumb lever on handlebars. Problem is nothing gets displayed except the error message.

How difficult is it to read or copy existing LCD display programming/configuration from one display unit into another unit?
How similar do these LCD displays need to be? Same brand? Same part number?
Or do they only need to have compatible cables?
All three of our LCD displays have identical 5 pin connectors to plug into the bike's wiring harness.