Solved! Problem connecting Xiaoxiang BMS

[jai134]

See last post for answer I have a Xiaoxiang 6S-22S 250A continous current BMS. I try to connect it but I don't have any luck. My problems are that the app shows one extra cell, I can not charge it to 4.2V/cell (it's modules from a Nissan Leaf gen 1) the charget stops at 3.8-3.9V/cell and there is connection for a switch that does nothing after what I can see.
It is a quite staight forward install with BC0 lead to battery -, BC1 - BC12 (in my case 14S) to 1-12:th cell, all the remaining leads to cell 13 except the last one that goes to battery +. When I open the app I have correct voltage but one cell too much. 15 cells where no14 is 0V. I tried a 10S setup and got 11 cells and 10:th cell 0V.

I have "polymer normal" setting in parameters and 4.25V as overcharge value but it stops charging at 54.5V, 3.89V/cell when 14S, 38.9V, 3.89V/cell when 10S. My charger is built for 58.8V cutoff.

There is a connector with red and black leads which is marked "Switch" and according to their support it is just a switch so I tried to connect red and black together. I couldn't notice any difference.

This is really frustrating. Any help is appreciatedr

 

[jai134]

Yes. Here it is. Problem is that this diagram doesn't show my actual bms. Mine is up to 22S.

 

[jai134]

And here is a link to my google photo how it is connected. https://photos.app.goo.gl/3zVn9DUmhw3awoUA9

 

[jai134]

And a screenshot from the app

 

[jai134]

I have correct voltage at the connector. I measured it at the pcb side of the serial connector. And it is not the last cell that reports 0V, it is the second last, isn't it?

 

[jai134]

I have a Daly BMS that works. Downside of that one is that it is the bottleneck (can I use that word for the thing that is limiting my system?) and the new bms allows more power before it cuts off. I also like the flexibility it gives to have a BMS that can "grow". But now I think it is not me that did something wrong. Thank you for your kind help

 

[eee291]

The BMS may have been connected incorrectly.
You showed a video of the cells, but not BMS.
I'd like some pictures of the BMS if you can, please.
Do you have BC0 connected to B- as well?
It needs to be connected to BMS main B- as well to display voltages properly.


It says in the description to contact them for the wiring diagrams.
https://www.aliexpress.com/item/1005004279838433.html
This is the original manufacturer, they should be able to help.
I wrote them just in case.

 

[amberwolf]

And here is a link to my google photo how it is connected. https://photos.app.goo.gl/3zVn9DUmhw3awoUA9

I don't see any photo showing the cell connection to the BMS. There's a video that appears to show the cells.

I recommend, just to ensure there are no wiring errors, that you trace out the actual wiring you have done while drawing it out on paper, then measure each wire for continuity from the cell to the contact of the connector. (there will be no voltage across any of the wires measured this way as long as they have proper continuity, so it would be safe to do a continuity test if the wiring is correct. Otherwise a voltage test across the same ends of each wire, performed first, would ensure there is no voltage present to damage a meter set to continuity mode). Or disconnecting the connector from the BMS first, so there can be no current path from one end of a wire to the other).

I've found that it is very easy to "see" all the connections in something with more than a couple of wires to be correct, when in reality one or more of them is actually not correct, or not even connected; I've had numerous projects where drawing a diagram as I wire things up and then double-checking that diagram to the wires has prevented such mistakes (and sometimes saved significant money by not blowing things up or setting fire to the wiring. )

 

[jai134]

The BMS may have been connected incorrectly.
You showed a video of the cells, but not BMS.
I'd like some pictures of the BMS if you can, please.
Do you have BC0 connected to B- as well?
It needs to be connected to BMS main B- as well to display voltages properly.


It says in the description to contact them for the wiring diagrams.
https://www.aliexpress.com/item/1005004279838433.html
This is the original manufacturer, they should be able to help.
I wrote them just in case.

The connection diagram I posted is from their support.
I have tested every single wire, first for continuity and after connection, for voltage. Then I measured them all on PCB side of the connector after I connected it to the BMS.
I think that my video shows BC0 connected to B- and the cables from B- to the BMS (even if the BMS is not visible)? Is it something wrong there? It is the black wire, top left, in the beginning of the video..

 

[jai134]

Here is a photo of the BMS. I have only one cable from B- and C- now. I had two when I made the video. What is confusing is the colouring of BC14 and 15. The diagram does not tell. I guess that the red ones in the diagram are the wires that I should connect together. Not the actual color of the cables.

 

[eee291]

Looks like customer service is severely lacking

They didn't send me any sort of mail.

If you give up on the BMS, would you be willing to send it to me?

 

[jai134]

Thank you for trying! I have two more experiments to do but if they fail I will PM you

 

[eMark]

Have you used your DMM to check the individual Leaf cell voltages across each of the battery connections ... https://photos.app.goo.gl/3zVn9DUmhw3awoUA9 ... contact DMM probes to B12 and B13, then B13 and B14, then B14 and B15.

Be interesting in itself just to see how close your DMM readouts are to the app voltage readouts. At least you'll determne if B14 is as healthy being within the 0.006V variance of the other 14 Leaf cells.

 

[jai134]

Yes I have. I think it could be a faulty MOSFET. Can it?

 

[jai134]

BC0 top left to B- and BC22 bottom right to B+ isn't that right?

 

[eee291]

All balance wires are available for 6-22S. The remaining wires get shorted together just like in the diagrams above

 

[jai134]

All balance wires are available for 6-22S. The remaining wires get shorted together just like in the diagrams above

Yes, thats correct. I will try a 20S tomorrow and see if I get 21 cells. If so, I think I can start removing one wire at the time and see which one that does not change anything. I beleive that can point me to the faulty component..

 

[999zip999]

I have a 20s from the same company. My trouble was finding a good working app. But have one good one now the one with the elephant.

After saying this I think it's a wiring problem No I didn't install it in my pack. I had it made. Good luck and looking forward to a good result.

 

[eMark]

When I open the app I have correct voltage but one cell too much. 15 cells where no14 is 0V. I tried a 10S setup and got 11 cells and 10:th cell 0V.

So 15 readout (3,887V) is actually 14 (same with 10S where 11 readout is actually 10). Seems like a simple enuf problem to fix with a little rewiring correction of BMS lead wire connector (somehow present wiring is bypassing 14 to 15).

Otherwise use as is ... shouldn't be a problem(?).

I have "polymer normal" setting in parameters and 4.25V as overcharge value but it stops charging at 54.5V, 3.89V/cell when 14S, 38.9V, 3.89V/cell when 10S. My charger is built for 58.8V cutoff.

Hopefully you can find a way to charge 4.10V/cell. If 3.89V/cell is enuf capacity for your travelling distance ... without draining cells below say 3.20V ... then leave well enuf alone, as it will prolong cycle life longevity of your salvaged Nissan LEAF cells.

 

[jai134]

Could it be the big difference between 3.89 and 0V that makes it stop charging? I don't really care if it shows 14 or 15 cells as long as it protects my battery but can I be shure of that?
No, it is not enough for my riding distance. I have 40-50 km when I charge to 58.8V.

 

[eMark]

Have you used your DMM to check the individual Leaf cell voltages across each of the battery connections ... https://photos.app.goo.gl/3zVn9DUmhw3awoUA9 ... contact DMM probes to B12 and B13, then B13 and B14, then B14 and B15.

Be interesting in itself just to see how close your DMM readouts are to the app voltage readouts. At least you'll determne if B14 is as healthy being within the 0.006V variance of the other 14 Leaf cells.

So you really didn't use your DMM to test those cell voltages as there is no B15 cell. Was expecting you to say so

Use your DMM to measure cell voltages on cells ... B11 to B12, B12 to B13, B13 to + (B13 to + is B14).

 

[jai134]

I don't understand?

 

[eMark]

Use your DMM to measure cell voltages on cells ... B11 to B12, B12 to B13, B13 to + (B13 to + is B14).

Wrong again! Where's B14? -- "B13 to +" does not make B14. Wanted to see if you caught the obvious error of my last post. Apologize for confusion -- see how you'd reply to obvious error.

I don't understand?

Rightly So! Is the following accurate of how the BMS lead wires are connected to LEAF cells?

- (BMS negative lead wire #1) connection to B1-, B1+ to B2-, B2+ to B3-, B3+ to B4-, B4+ to B5-, B5+ to B6-, B6+ to B7-, B7+ to B8-, B8+ to B9-, B9+ to B10-, B10+ to B11-, B11+ to B12-, B12+ to B13-, B13+ to B14-, B14+ to + ... altogether 15 lead wires (- to B1- is (negative) BMS lead wire #1 ... B14+ to + is (positive) BMS lead wire #15.

Most likely your BMS connector lead wires to the 14 LEAF cells is correct. If you have a DMM that reads to 3 decimal places thought you would be interested to see how close (within a few millivolts) to the 'smart' BMS app voltages to 3 decimal place readings. That way you can then verify that voltage B15 (showing on your 'smart' BMS app) is actually B14 voltage.

Most likely you have the 15 lead wires (from -) correctly connected to the 14 LEAF cells (to +). That suggests that the BMSs connector wiring itself is askew. With some diagnostic testing help from other ES members that are BMS Smart you hopefully can correct the BMS wire connections so B14 reads the same voltage (that is now shown on B15) and B15 is no more.

Have you measured the output voltage of the charger with your DMM? It's possible it's only putting out 54.4V. If so there should be a trim pot that you can adjust to up the voltage output to 57.4V (4.1V/cell).

 

[jai134]

Thank you very much! I can only read two decimals on my DMM.
My charger is ok up to 58.8V. I know it because it did when I had my other BMS connected.
I will go back to my old BMS for now because I want to ride my bike. Summer is short and my holiday will end soon :-(

EDIT! I am up and running with my Daly BMS. 14S and charging without problem

I think I solved the charging problem with the other BMS last night. 3.9 x 15 = 58.5 and therefor it beleives that 3.9 is ok because of the non-existent 15th cell. Charging 15 cells to 4.2V would give 63V which is too high.

 

[jai134]

After two angry e-mail yesterday I finally got the correct wiring diagram from their support. I don't understand why they can't ship a diagram together with the BMS..
So, now I have a test pack, 6S, charged to somewhere around 4.1V. I will finish it tomorrow and see how well it balances the pack.
Here is the correct way of connecting the bms