mclarin89 Posted November 4, 2021 Share Posted November 4, 2021 I was riding my s18 and had a minor spill. When I picked it up it started doing the rocking forward and back thing it does when the battery is at 0%. I opened EUCworld and it showed the voltage at 58v and 0% charge. It was about 80% charge right before the fall. When I got home I unplugged the batteries from the motherboard and checked them with a volt meter. Both front packs are at 79v and both rear packs are at 39.5v. I then opened up the batteries to check the cell voltages and they were all between 3.94-3.97v. So I'm trying to figure out if the incorrect voltage reading is from a bad motherboard or bad BMS in one of the packs. Each pack has 4 wires, the two large positive and negative discharge wires, a small negative charging wire (blue), and a small green wire which I assume is the BMS sync wire. (Note, the right rear battery does not have the blue cable because the two rear packs are wired in series and only 1 negative charge cable is needed for the pair) I measured the voltage from battery negative to the green wire and got 11.5v on both of the front packs and the left rear pack, but the right rear pack is 19.3v. I wonder if this means the BMS in the right rear pack is broken? Does anyone know if these voltages are normal? If all 4 batteries are good, I'm guessing it's a problem with the voltage divider on the motherboard, like this post talks about Perhaps the C1 capacitor got damaged in the fall. And by the way, incase anyone is wondering about the s18 BMS, here's what I see. It has the typical 100ohm bleed resistors on each cell that every BMS has. It also has a neotec NT1664 to disconnect the negative charge lead when any cell goes above 4.25v. There are also 5 parallel FETs on the negative discharge cable for overcurrent/short protection. And finally, there are 3 smt fuses in parallel in each BMS. Interestingly, the 2 rear packs each have a NT1662 (10 cell version of NT1664), but since only the left pack has the negative charge cable, it can only disconnect charge if one of the cells in the left pack is over 4.25v. Maybe the NT1662 in the right pack sends a signal via the green wire if one of its cells is over 4.25v? 3 Quote Link to comment Share on other sites More sharing options...
Chriull Posted November 5, 2021 Share Posted November 5, 2021 Welcome! 7 hours ago, mclarin89 said: I was riding my s18 and had a minor spill. When I picked it up it started doing the rocking forward and back thing it does when the battery is at 0%. I opened EUCworld and it showed the voltage at 58v and 0% charge. It was about 80% charge right before the fall. When I got home I unplugged the batteries from the motherboard and checked them with a volt meter. Both front packs are at 79v and both rear packs are at 39.5v. You checked if the battery voltage arrived at the motherboard? So connectors and cables are ok? Don't know/remember if the S18 works with just one battery (at a special place - just front or back?). Anyhow - you could try the different combinations. Maybe you get valid reported voltages again and can rule out some possibilities/track some bad pack? 7 hours ago, mclarin89 said: So I'm trying to figure out if the incorrect voltage reading is from a bad motherboard or bad BMS in one of the packs. Voltages are measured on the motherboard and reported by the motherboard. As you measured valid ouput voltages at the unplugged battery connectors the malfuntion should be at the motherboard? 7 hours ago, mclarin89 said: Each pack has 4 wires, the two large positive and negative discharge wires, a small negative charging wire (blue), and a small green wire which I assume is the BMS sync wire. (Note, the right rear battery does not have the blue cable because the two rear packs are wired in series and only 1 negative charge cable is needed for the pair) I measured the voltage from battery negative to the green wire and got 11.5v on both of the front packs and the left rear pack, but the right rear pack is 19.3v. I wonder if this means the BMS in the right rear pack is broken? Does anyone know if these voltages are normal? They are using the overvoltage cut-off output of the overvoltage monitor. I'd guess that these sync wires are "open" collector outputs - so they can be used as a wired or. If so the output voltage depends on your Voltmeters internal resistance in relation to the transistors if they are not triggered. Maybe @RagingGrandpa has some more details for the "Charge-Stop trigger link", as he calls it in It's Gotway, but some details are very similar between some brands - could easily be that this sync link was a "development" from ancient times when GW/KS were still one company. 7 hours ago, mclarin89 said: If all 4 batteries are good, I'm guessing it's a problem with the voltage divider on the motherboard, like this post talks about Missing/ruptured parts should be "easy" to find?! Maybe the connection between the battery connectors until the measurement is somewere broken. You checked the fuses? S18 has the fuses on the motherboard, too? Does the S18 has charge current measurement as the/some 18XL had? So some more parts that could be ruptured. 7 hours ago, mclarin89 said: And by the way, incase anyone is wondering about the s18 BMS, here's what I see. It has the typical 100ohm bleed resistors on each cell that every BMS has. It also has a neotec NT1664 to disconnect the negative charge lead when any cell goes above 4.25v. So a F1A version used? Nice detail -thanks! 7 hours ago, mclarin89 said: There are also 5 parallel FETs on the negative discharge cable for overcurrent/short protection. And finally, there are 3 smt fuses in parallel in each BMS. Fuses in parallel?! Shiver... reminds a bit on playing russion roulette 7 hours ago, mclarin89 said: Interestingly, the 2 rear packs each have a NT1662 (10 cell version of NT1664), but since only the left pack has the negative charge cable, it can only disconnect charge if one of the cells in the left pack is over 4.25v. Maybe the NT1662 in the right pack sends a signal via the green wire if one of its cells is over 4.25v? Hopefully. 7 hours ago, mclarin89 said: I then opened up the batteries to check the cell voltages and they were all between 3.94-3.97v Nice! You remember about how the distribution of the voltages was? Checking from time to time the cell voltages can be a nice battery state supervision - just nicely wrapping the pack afterwards is important - humidity is no friend of battery packs! I did a simulation on passive BMS balancing I'm just missing the "mechanism on how cells age/degrade by which burdens". My assumption is that single (a low count) of cells start the progress. Most "degrading" happening at high burden low discharge stages. A "heavily" used 3p wheel like the S18 could be a nice "study object" for this 1 Quote Link to comment Share on other sites More sharing options...
RagingGrandpa Posted November 5, 2021 Share Posted November 5, 2021 (edited) 13 hours ago, mclarin89 said: I measured the voltage from battery negative to the green wire and got 11.5v on both of the front packs and the left rear pack, but the right rear pack is 19.3v. I wonder if this means the BMS in the right rear pack is broken? Does anyone know if these voltages are normal? Sorry, I have no personal experience with Kingsong BMS. I recommend confirming "What is the actual voltage present at the FET capacitors?" (because this is after the many shutoff devices, and is the voltage that drives the EUC). I think you could probe the capacitor's legs carefully from the top-side of the control board. Carefully! If you see >80V here, and <60V reported to the app, I would recommend trying another controller. Not convenient, sorry. Also be sure to try connecting only 1 pack (a 20s front pack, for example) to the controller, and checking the reported voltage again. 13 hours ago, mclarin89 said: small green wire which I assume is the BMS sync wire Since you're already inspecting BMS PCB's, perhaps you could discover which circuit of components drives the green wire? Edited November 5, 2021 by RagingGrandpa 1 Quote Link to comment Share on other sites More sharing options...
Brendan "nog3" Halliday Posted November 5, 2021 Share Posted November 5, 2021 On the front two packs measure the voltage between the blue/green two smaller cables on the packs, they should be around 12v. If they're much lower then the pack does not test as OK. For the rear, one side blue/green should also be around 12v, and for the other without the blue wire check between green and black (bigger pin). Supposedly the right rear being closer to 15 or 20v is normal. 3 Quote Link to comment Share on other sites More sharing options...
mclarin89 Posted November 5, 2021 Author Share Posted November 5, 2021 (edited) Brendan thanks for the info that's exactly what I was looking for! RagingGrandpa good idea, I measured the voltage across the motor driver FET caps on the motherboard and got 79v. I couldn't easily trace what the green wire is connected to but I'm guessing it's connected to the charge cutoff FET gate and the NT1664 output based on the NT1664 datasheet. Since the right rear battery doesn't have a charge cutoff FET, the green wire is probably connected to the NT1662 output only. That's a plausible reason for the right pack to have a different voltage on the green wire and Brendan confirmed it should be different. Chriull I don't see any fuses on the motherboard, just in the batteries. I agree fuses in parallel is slightly questionable as the total amp rating will be a bit less than the sum since they won't share the current totally equally and once one goes they all go. Most of the cells were 3.94 and the 3.97 ones were all next to each other. For example, one of the rear packs was 3.94, 3.94, 3.97, 3.97, 3.97, 3.94, 3.94, 3.94, 3.94, 3.94 Yes it's the F1A version. So it seems like the voltage divider or the processor ADC channel on the motherboard is bad. I was hoping I could find the voltage divider and measure if the voltage is what it should be based on the resistor values and replace the resistors if it's off. If the processor ADC channel is bad then nothing I can do. Any way, with ~200 resistors on the board and several dozen covered in silicone, I'm not having any luck finding the voltage divider. Edited November 5, 2021 by mclarin89 bold names 1 Quote Link to comment Share on other sites More sharing options...
RagingGrandpa Posted November 5, 2021 Share Posted November 5, 2021 Boards are cheaper than batteries, at least 1 Quote Link to comment Share on other sites More sharing options...
mclarin89 Posted November 5, 2021 Author Share Posted November 5, 2021 Yep, I'm thinking order a board and then starting ripping silicone off my current one. If I break it I'll just use the new board. If I fix it I'll still use the new board any way but at least I can share how to fix the voltage divider. 1 Quote Link to comment Share on other sites More sharing options...
5Cauac Posted November 5, 2021 Share Posted November 5, 2021 FYI, If you are going to get a board through Ewheels, be prepared to wait a few weeks as they are waiting on a shipment of "essential" parts after the fire. I happened to pop another MOSFET the day they had the fire and did not know of the news until after I had send them my request. Quote Link to comment Share on other sites More sharing options...
mclarin89 Posted November 17, 2021 Author Share Posted November 17, 2021 Got the new board in, voltmeter and eucworld agree within 0.5v. Much better than having a 20v disagreement 2 Quote Link to comment Share on other sites More sharing options...
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