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Xiaomi/Ninebot/Segway "MiniPro" No Longer Working

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Bought a Segway/Ninebot MiniPro with the GoKart kit (Ninebot Gokart PRO), but it is the Xiaomi, non-US, non-UL version from China - this one was branded as "Anything Sports" but similar units can be Xiaomi NO.9, Xiaomi Mi Scooter Mini, etc. Guy had totally messed up the wiring for the GoKart - was only using two wires from the 4-pin connector, appears to have added a motor controller that was supposed to be there, etc. After mapping out the wiring, I think he just needed a frame spring line. At first, the MiniPro worked using the BT remote; not sure about balance mode, but there was motion when I first put my foot on there, so I am guessing that was working, too. Now, the unit doesn't move. I can connect with a number of apps (including MiniRobot, which is the recommended app), I can see info such as temp, battery life, knee support angle, speed of wheels when manually turned, etc. The "Current operating mode" is always "stand-by," except when I lock the unit, then the mode is "Immobilization." I was also able to put it into karting mode originally, but can't do that anymore. I have taken the unit completely apart, including the battery, and see nothing wrong. While I am technical, I am not very adept when it comes to electrical, but I plan to learn the basics and then some through this project and other things I am working on - mainly so that I can teach the kids. I would like to fix this unit, but if there is going to be a high cost, high risk venture since some parts are different, I don't see why I can't remove the majority of the components, add motor controller(s) and use the unit without balance since the kart is designed to fit this unit perfectly.



Here is the longer version...


What I purchased:


GoKart package




MiniPro/Xiaomi Mi



But the wheels on mine look like the wheels on these:




The day I purchased this, it was working. I did not ride it, but when I put my foot on the pad, the unit moved. When I got home, put the gokart kit on and was able to use the MiniRobot app to control it (not very well) and see all of the information from the unit. I could not use the gokart kit using the gas/brake since the guy had configured his own wiring, which resulted in only the horn and light working.


Later on, the unit stopped responding to both BT controller and stepping on the pads.


The scooter powers on, lights work, BT works, etc. The one time I opened it up, I went ahead and unplugged the speaker. When you would turn it on, it says something about bluetooth ready to connect - but ridiculously loud. I had tape over it to help, but it was still too loud.


I have completely broken this unit down (multiple times) - I saw nothing unplugged, nothing seems to be burned out, basically nothing obvious. I even opened the battery and made sure everything looked good in there.


I can connect to the unit using the MiniRobot app as well as a few others that I tried - most of which were made by the same developer, Lebitec. When connected via BT, I can still see temp, speed, battery life, knee support angle when moved, etc. When I try to control the unit using the BT remote, the signal is being sent - I can hear some "noise" in the unit as if it is processing the command(s), but nothing else happens.


At one point I thought the issue was the DB9 connector. The male and female parts are on different sides of the board and there is nothing hold the male side in place, so reconnecting it was hella difficult since you couldn't just push it in without somehow holding or pushing from the other side. You also can't see if it is plugged in or not, you have to go by feel.


In the app, the unit is always in stand-by mode, unless I lock the unit. If I lock the unit, it then changes to immobilization, but I never have any other status showing. If I try to change it to karting mode (which worked day #1), it says: "the kart mode switch balance car mode requires the card to be placed upright" and does not enable.


I would like to fix this unit, but if I need to start replacing parts, which MAY be difficult since they may need to come from China directly, then I would like to use the unit as-is (control the motors, but not balance). This is where I will need a little bit of guidance. I have been on literally hundreds of sites trying to figure out what is going on with this one and also how to "convert" it to go-kart only. Most projects like this are for scooters or bikes with only one hub motor, whereas I will be working with two. I think this will require two controllers, but I am not 100% sure. I understand basic electrical, but mostly just two-wire motors for small projects. Three-phase is new to me. I did perform the test where you touch two wires and make sure there is resistance when turning the wheels.


Here are some of the specs:


10 inch/255mm wheels

voltage: 54V-63V

No-load current: 0.45A

rated power: 350W x 2

Hall angle: 120 degrees

Polar logarithm: 15 poles

Speed 580 rpm

torque: 9.5N/M

battery: 36V 4.0AH or 54V 4.0AH

mainboard version: b.2.1 (0000:0b.2.1:220a)

BT version: 2.8.2 (02)


I have placed a bunch of pictures that I took of the unit, screenshots from various apps, as well as images of the unit, gokart, and parts that I found online.https://photos.app.goo.gl/wb13u8rTp3vvKMYz6

I am sure I forgot to mention some things, but I will edit this post if I think of anything or to answer any questions you might have. Thank you in advance to anyone that is able to offer some advice.

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