Hi all! I´m new to this forum and new to the onewheel world! I just got a faulty XR (very bad condition) and I´m trying to resurrect it... which looks challenging at this point. I saw that there is a high level of tech knowledge here, so I wanted to see if you could help me on this:
HW: 4212 (lucky me)
SYMPTOMS: Error 16; battery not charging.
FIRST GUESS: BMS fried
Upon opening up the battery box, I see C11 missing, which is a 1uF capacitor. I also assume that the voltage should be for the cell, which should be 4.5V (I saw on other designs that the voltage covers the total voltage of the entire battery pack -63V-). If my assumption is correct, I would go for a 1uF 10V ceramic capacitor.
I checked RS-485 comms. Resistance appears to be OK (121 ohm between terminals). However there is continuity between terminal 5 (GND) and 8 (Vcc) in the SN65HVD1786. Looks like it is fried and has to be replaced. C33 it is also shorted and has to be replaced (100 nF - 220 nF 6V ceramic capacitor)
I also checked the PIC to see the status of it, since it is the driver of the comms. Terminals 16 (Vss) and 17 (Vdd) are shorted. BUT I didn´t check yet if it is due to the capacitors installed between these pins (C34 and C35 which I honestly don´t know the value) OR to a short on the PIC internals. If I decide to replace the PIC I would have to program it with a firmware... which I do not have. Those capacitors are installed between Vdd and Vss. Difficult to see the traces, but I assume it by the position and continuity.
On the controller side, SN65HVD1786 is good and R=121 Ohm (at least something good). I assume the controller side is OK.
So at this point I don´t know how far should I go with this because I have some limitations (never soldered SMD, BMS PIC Firmware missing). I have some questions to see if you could give me a hand...
1.- Does anybody know if the firmware for BMS 2110 pcb is available? or any custom firmware to flash? (I can program PICs, that should not be a problem, but I do not have any .hex)
2.- Has anybody tried to flash the PIC of a 4212 BMS with an older BMS PCB? (i.e. 4209)
3.- (this is the tough one) Does anybody know the value of the C34 and C35 capacitors? Are installed between Vss and Vdd of the BMS PIC ucontroller, and are REALLY tiny. I cannot find information about them.
Besides that, the XR has most of the screws missing, no bumpers or fender. I guess I will spend some time on this one...
Thank you guys!!!
Welcome to the forum :)
Do you have any pics of the BMS to take a look at? The knocked components are a bit odd, prior repair attempt maybe?
Since VCC and GND are shorted across the RS-485 chip that'll be the primary reason E16 is showing up. Probs best to try desolder that and see if the short remains in case it's being pulled down elsewhere (hopefully not)
C11 being one of the caps coming off a balance line isn't helping either. Each cell should be no more than 4.2v too rather than 4.5 0.o
Sadly don't have any answers to the other questions. That said there are a number of others here that have way more knowledge on. They'll be bound to chime in soon x
@lia thank! Well, for the cells voltage… didn’t measure -_-u. It was only to see the voltage for the capacitor; somewhere bigger than 4.5 should be fine.
To be honest… i don’t know what happened to this board, the previous owner opened it and i don’t know what was done… but it’s a disaster. After all these issues i was expecting a “lucifer was here” on the back of the board. Once i arrive home i will take a picture of the board. I think that if this bms pcb is the same as an older one i could get the fw and flash it. But, as you say (and nkotb knew) step by step. I’ll start with the rs-485 replacement and i will also desolder the capacitors to see if it is on the pic or not.
@vulkito Ah no worries then. For a second I was worried you meant those cells were 4.5v lol.
Sounds like it could be a fun fix. Keep us in the loop with how that goes :)
@Sirgu Aha True but I never had to flash anything thankfully. Although it get very close to that. Thanks for linking the old thread :)
@sirgu thank you! I hope so… it is my opportunity to finally have my one wheel! Hahaha
bms 2110 here is the bms board. For the record xd
@vulkito Oh yeah I see the knocked cap on C11. Bet that was the previous owner pulling the XT60 out and accidentally catching it.
@lia yeah, i bet that the previous owner didn’t put too much effort on opening this up and i doubt he followed the disconnecting order of these connectors (which could also be the origin of this). In any case: i ordered a new rs-485 and i will look tomorrow for capacitors, but those on the pic… i have no idea of what to use there (i would say those are generic capacitors on the input, but the values is a different matter…)
@vulkito The 4212 bms pic 1788 chip is locked and cannot be flashed. The chip has to be replaced , however you can use an earlier XR bms with the newest Owie chip.
You can reflash a Pint bms to Xr.
I bought a couple of 1788 chips in case.
@vulkito What happened to the pictures of the bms, I can't see them.
@lemur i hve a couple of pics in my cart already hehehe. But now the question would be if i can install a new pic (flashed with an old firmware revision) and would work (+owie). I would say that the hardware at logic level is the same (but i do not have a board to compare). If this is the case i can search for a 4209 firmwware and test. The bms is already out, soooo i guess there is nothing to lose xD
@lemur i can see them on the link. Does it guve you any kind of error?
@vulkito Oops, didn't click on the link.
Ok, some news:
C33, c34 and c35 are ok. Removed from the pcb to try to isolate the short with no luck (at least i measured the cap values).
I desoldered gnd from the 1786 and looks like that this one is not shorted either. I still have a short between gnd and vcc, so either the pic is shorted or i think i should go to the voltage regulator (which i have to look for on the power area). This sounds promising… (i’m starting to lose faith…)
@vulkito It'll show itself soon enough.
Using a low voltage (lowest voltage present on the board to minimise additional damage just in case) fed into the problem power rail you can then run a finger over the PCB till you feel something very warm. That'll likely be the shorted component.
In the worst case a replacement BMS using the previously mentioned OWIE chip can break the serial lock and allow a board to function again.
@lia thank! That is actually a great idea! I’ll try tomorrow and will let you know ;)
Ok, after injecting V to the rail with my power supply the limitation was triggered and nothing was hot. I connected everything back (batt and controller) and turned the ow on. Error 16 came up and the max was really hot compared to the rest of the components. I guess we got the culprit. Now we’ll see how the replacement goes. I’ll keep you posted!
@vulkito Good find, which component was it getting hot?
@lia was the max battery management chip (max 14921). I wasn’t expecting that…