Meet One Tour is dead

[buffalo]

Hello,

our Meet One Tour died today.
First it displayed a 51 error briefly, then 76 and after a few power cycles with a few meters driven, it did not turn on any more.
Batteries are full.
Also when rolling backwards and front motor plugged in, there are strange noises coming from the front motor.
If unplugged the motor rolls backwards silently.
Till it died, everything was just fine.
Still waiting for the Manufacturer to respond, don't know yet if we get any help.
Any ideas how to start the troubleshooting?
I've got a multimeter and basic eletrical knowledge.

I've created a rough schema of the electrical system.
Also there are some images to get an idea.
The internet never heared about these product numbers. Probably OEM stuff.

In case the manudacturer cannot help: Are there reliable dual motor controllers that I could use instead?

Motors are dual 750W hubs.

This is written on the devices:
Dual Battery Equalizer
Yolin-DBE-(20V~55V)-50A
20250703-0147

Controller for brushless motor
Rated voltage: 48V
Maximum current: 25A
Rated current: 12A
Low voltage protection: 39V
Throttle adjustment voltage: 1.2V-4.4V
Product number: LSQ1854-05-02U-A X2504007036
Product number: LSQ1854-05-02U-B X2504006886
Ex-factory date: 04 2025
www.lsdzs.com

Display
91F4820299Y060X
20250305X0112 Yolin

And another Yolin device without any descriptions.

Thank you!

 

[E-HP]

Unplug the motor cable and try rolling backwards again. If it rolls smoothly then you controller's FETs may have shorted/fried themselves. There are Lishui controller experts on this forum, so someone may chime in with more input.
If you disconnect "5" from your diagram, the connection between the two controllers, will the rear motor run?

 

[buffalo]

As written above: "If unplugged the motor rolls backwards silently."
It does not turn on currently. Neither with both controllers connected, nor disconnected.

 

[E-HP]

As written above: "If unplugged the motor rolls backwards silently."
It does not turn on currently. Neither with both controllers connected, nor disconnected.

So disconnecting 5 didn't do anything?

I would test the motor(s) and controller(s) for obvious problems first. It would be unusual for both controllers to die, but it sounds like there's at least an issue with the front motor controller:

 

[buffalo]

Thank you for the video.
It is already dark outside, so I'll have to wait till tomorrow to measure both controllers and motors.
Will report back.

 

[buffalo]

The front controller has one phase shorted to ground. The other 2 phases have 20kΩ resistance. Against V+ they all have ~240kΩ.
The rear controller has all 3 phases at 20kΩ to ground and 285kΩ to V+.
The Yolin dual battery balancer outputs 52.5V on both outputs.
The display does not turn on either with the front controller connected nor disconnected.