czarodzi Posted May 10, 2021 Share Posted May 10, 2021 Last week I found a two-wheeled device in a dumpster which - in total seriousness - looks like it was used as the mall cop patrol vehicle! Getting it cleaned up in the garage and looking it over, it's a Segway ninebot miniLITE, model N4M160. At this point it does nothing - no lights or sounds or movement. There's one flat tire and one wheel that doesn't rotate smoothly. I didn't find a charger or anything, so first things first I'm ordering one. It looks like there's a lot of information here for it and related models so I hope to make some progress and I'll post updates here. Any troubleshooting tips, please pass them along! 1 Quote Link to comment Share on other sites More sharing options...
RockyTop Posted May 10, 2021 Share Posted May 10, 2021 The one wheel not rotating smoothly is a concern. Does it turn smooth if you turn it very slowly and then just about lock up if you turn quickly? If so the board with the MOSFITs is likely blown. Quote Link to comment Share on other sites More sharing options...
czarodzi Posted May 11, 2021 Author Share Posted May 11, 2021 8 hours ago, RockyTop said: The one wheel not rotating smoothly is a concern. Does it turn smooth if you turn it very slowly and then just about lock up if you turn quickly? If so the board with the MOSFITs is likely blown. Good question. I removed the battery to get at the circuit board and disconnected the three larger connectors for Motor2 (which I'm guessing are for the power) and it turns a little more smoothly but still has an intermittent grinding sound, and it still doesn't really spin freely. The grinding is like if there's sand or grit in a bearing. The wheel on the other side does spin smoothly when the wires are disconnected - when I give it a good spin it does a little over a full rotation spinning on its own. On the side which grinds I see six power transistors, one of the legs on one of the six has white residue that might be corrosion... when I get time I'll get the board out to see the top side and try to re-solder that one point, and as a test I could probably swap over the good wheel to try spinning it while connected on that side. Are the MOSFETs common parts that might be replaceable (or does something else delicate and expensive on the board burn out before the high power components?) 1 Quote Link to comment Share on other sites More sharing options...
RockyTop Posted May 11, 2021 Share Posted May 11, 2021 Ahh! OK, In that case one of the wires to the motor may have disconnected. (burned up, corroded , wire broke) That could cause the motor to single phase and burn up. You have two motors you could test the good motor on either side to see if the board (MOSFITs) is bad. If the board is bad (shorted) the good motor might not spin freely on the other side. It could be bad and open, The motor would spin freely because the circuit is open. If you do turn it on don't let it vibrate or hum. turn off or disconnect. Quote Link to comment Share on other sites More sharing options...
czarodzi Posted May 14, 2021 Author Share Posted May 14, 2021 Some further troubleshooting: The good wheel has the same "catch" in its rotation on the bad side; in other words that wheel rotates totally smoothly on the good side of the board, but has that intermittent slowdown when connected to that bad side. I tried re-flowing the solder on the output transistors and the problem remains. It may be that one, or a pair, of output transistors is bad. With two of the three wires (Yellow and Brown) connected to the good wheel it rotates a little more smoothly, and that is the same when connected to the two wires (Yellow and Brown) on the good side, so two phases may be good. Suspecting it's the transistors on the Blue leg, I started probing with a meter. The two output transistors on the bad side appear to be shorted - from either of the power terminals on the top edge to the connector on the Blue wire I get continuity. I'm going to do some further testing and may desolder and clean up those transistors over the weekend so I can see what to order. 1 Quote Link to comment Share on other sites More sharing options...
RockyTop Posted May 14, 2021 Share Posted May 14, 2021 If you get the part numbers you should be able to order the new parts fairly cheap online. Quote Link to comment Share on other sites More sharing options...
czarodzi Posted May 30, 2021 Author Share Posted May 30, 2021 OK, a little progress to report. Once those transistors were out, getting the part numbers was easy enough: STP15810, STMicroelectronics power MOSFET. Easy to find and cheap to buy but slow delivery.... They arrived this weekend and I was able to get them soldered in. Again with the meter, they test out OK, and with the one good wheel connected it rotates smoothly, like the other side had all along. Sure would be good to get this powered up to test.... However the next big issue is the battery. I left it on the charger for about two hours and the charger light went from red to green but the battery itself has no lights. I tried the wires to the output terminal and the charger went from red to green in about 15 minutes but still no lights on the battery. The battery voltage was about 26 volts so I was thinking there were some bad cells inside, which again should be an easy fix. However, once I opened it up I saw drops of water rolling around inside and the battery charge controller board is badly damaged with arcing and corrosion. The pairs of cells do measure a little over 4 volts each and the whole pack is just about 42 volts so there's got to be some significant faults on the controller board. Any chance there's a replacement board out there, or another bad battery pack that might have a salvageable board? I do see there are other 36 Volt batteries but not sure how universal these things are. Quote Link to comment Share on other sites More sharing options...
czarodzi Posted June 19, 2021 Author Share Posted June 19, 2021 Progress is sloow but things are happening. I have the minilite re-assembled after getting a replacement motor, and I used wires with alligator clips to connect enough cells together to make 36 v, connected to the power connectors on the main board. It powers on and straightens itself up, and stays in that position - that is great to see! I can get it to move forward and back short distances, so functionally it's getting there. The point I'm at now, it blinks red lights and beeps, two then three. Looking at the error code references for some of the other mini models this is an indication that it's not communicating with the battery controller, which makes sense. I was thinking about getting a generic 36 v 2 p battery management board to repair the battery pack, which should get it all put back together enough to run, but it will probably leave it blinking and beeping the entire time. Is there any possibility I could do something with the signal pins in the power connector, like short them or insert a small-value resistor, like the chargers for phones and laptops? Quote Link to comment Share on other sites More sharing options...
czarodzi Posted July 12, 2021 Author Share Posted July 12, 2021 Ok, the generic BMS board arrived and it's installed. It was a hassle getting the power connector off the original (bad) board, and doing the individual connections between cell pairs for the circuit to work, but it's repaired and rolling! The repaired battery charges with the 42v power supply, the display between the foot pads shows the remaining power level, and it's working great! The flashing red lights continue and I did have to open up the "dashboard" to de-solder the speaker so it's not constantly beeping, but it runs for several hours - and miles - on a charge. Quote Link to comment Share on other sites More sharing options...
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