JK BMS JK-B2A8S20P RS-485 port / connector

[claib]

hi there
got my venus 2.91 on raspi up an running...
on my JK BMS, there is a port labeled RS485, wich has 3 pins.
Does anyone know which is A, B and GND ?
In the logs, i see the USB/RS485 adapter is working, but always get the ERROR, incorrect data.
So i assume i do not have the right pins connected.

any advice ?
best greetings
Christoph

[arrow1800]

does this help? in my case i had to use the port labeled with GPS :S

[Dighy]

Hi everyone,
I am a beginner here and need your assistance before to do something wrong.
My configuration is like in the picture attached by you but the difference is that my BMS is B2A8S20P for 8s battery.
The question is if it's ok to connect the USB to usb port in my CCGX from Victron or it's required cable to connect to VE Can port?
I have same module/ adapter.
Thanks 🙏

[Louisvdw]

As @arrow1800 mentioned you do need to use the GPS port for the RS485. (those are great pictures)
If you use the JKBMS RS485 dongle it will just plug in and you can use the 3 output wires (yellow A, white B, black GROUND) which you then connect to your RS485 to USB connector and into your GX device.
If you don't have the JKBMS dongle thingy, then you can use a TTL to USB converter. That plug is a 4 Pin 1.25mm JST using GND, RX, TX, VBAT. Please do not connect the Vbat as the voltage will be too high.

[Dr-Gigavolt]

Is the GPS connector TTL and not RS485? Bad news, I already ordered two RS485 to USB with galvanic insulation from China 😞. And they put Vbat to the tiny JST close to digital stuff? Not only dangerous, but useless too. Now I'm loosing the good impression about JK.

[Louisvdw]

That JKBMS dongle converts the TTL to RS485. So it's not a RS485 port but rather the port for the RS485 converter. Not the best labels 😞

[claib]

so a FTDI to USB cable : without RS485 converter ? Am Di., 11. Okt. 2022 um 10:57 Uhr schrieb Louis Van Der Walt < ***@***.***>:

…

As @arrow1800 <https://github.com/arrow1800> mentioned you do need to use the GPS port for the RS485. (those are great pictures) If you use the JKBMS RS485 dongle it will just plug in and you can use the 3 output wires (yellow A, white B, black GROUND) which you then connect to your RS485 to USB connector and into your GX device. If you don't have the JKBMS dongle thingy, then you can use a TTL to USB converter. That plug is a 4 Pin 1.25mm JST using GND, RX, TX, VBAT. Please do not connect the Vbat as the voltage will be too high. — Reply to this email directly, view it on GitHub <#250 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACAIWJLJLJUH6YTKWXONNLLWCUTXRANCNFSM6AAAAAARCAG4WM> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>

-- *Christoph Laib* *VIOS GmbH, Switzerland* *Speicherstrasse 27* *CH-9053 Teufen* M: +41 79 600 62 32 E: ***@***.*** ***@***.***> W: www.vios.ch

[ghost]

I found out my issue was just related to the 4-pin JST connector .... as soon as I changed it it worked. I'm wondering what is the exact type of connector to use here?...I had problems with a 4-pin JST MX 1,25mm connector.... it looked a little bit to small for me but I was able to plug it in....maybe someone also has a link where to buy? Thx Stefan

[ghost]

This was the connector I had problems with....

https://www.amazon.de/3-polige-Steckerbuchse-weiblich-m%C3%A4nnlich-Stecker/dp/B09F2C7SD5/ref=sr_1_2?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=36Z3PPR8TC167&keywords=winwill+jst+1%2C25&qid=1671491300&sprefix=winwill+jst+1+25%2Caps%2C98&sr=8-2

[Dr-Gigavolt]

It is a 3 pins connector, you need one with 4 pins.

[Dr-Gigavolt]

This was my source: https://www.ebay.de/itm/284259946599?mkcid=16&mkevt=1&mkrid=707-127634-2357-0&ssspo=-KjvLcpwRNS&sssrc=2349624&ssuid=2ty0aM6GR6a&var=&widget_ver=artemis&media=COPY

[ghost]

Sorry, my fault, I send a wrong link, I use a 4 Pin connctor from the same manufacturer, but it's not working reliable. Thanks for the link, i already ordered them and will give them a try!

[claib]

is this one working as well ? https://www.waveshare.com/product/iot-communication/usb-to-rs485.htm Am Di., 11. Okt. 2022 um 21:42 Uhr schrieb Louis Van Der Walt < ***@***.***>:

…

Waveshare has this one which should be available almost everywhere https://www.waveshare.com/usb-to-rs232-485-ttl.htm — Reply to this email directly, view it on GitHub <#250 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACAIWJIO356N45SBZIZWVZTWCW7MDANCNFSM6AAAAAARCAG4WM> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>

-- *Christoph Laib* *VIOS GmbH, Switzerland* *Speicherstrasse 27* *CH-9053 Teufen* M: +41 79 600 62 32 E: ***@***.*** ***@***.***> W: www.vios.ch

[Dr-Gigavolt]

The RS485 has differential signal line. For data transfer you need no ground. But if it is not isolates, the grounds of all units on the bus must be interconnected for potential equalisation, orherwise something will be blown up, sooner or later. If you use not isolated dongle, you must connect the grounds. Than everything will be ok until the BMS disconnect the - of the battery. The battery current will search another way and will find it - your tiny interface ground. Not good at all.

If your battery is close to the Venus device you don't need the RS485. Connect the GPS port by a screened cable to an isolated 3.3V serial to USB adapter of your choise. TX, RX inside, screen for the "ground".

[mr-manuel]

Thanks. In worst case I can put a little fuse on the ground of the RS485 connection with a very small current or will things still blow up?

[Dr-Gigavolt]

Don't do it. After burnimg the fuse you destroy the data line. The isolated serial to USB adapter that I use costs 7 EUR at China eBay and you are safe. Or if you want to use the dongle and RS485 you can have one or two isolated RS485 to USB from me. I bought them before learning that the BMS has no RS485 direct on board. In which country do you live?

[mr-manuel]

This is very kind of you, but you don't need to. I try to find the best option with less hardware as possible, so less parts can break.

I just found this USB to 1x TTL and USB to 4x TTL adapters which are galvanic isolated through a video from Off-Grid-Garage.
Now I have another dumb question. This adapter says USB to TTL UART FTDI. So you can use this adapter to connect VE.Direct devices. Should I then also be able to connect the JK BMS RS485 port (which is TTL what I understood now) directly to the VE.Direct port of my MultiPlus II-GX? Obviously in this case there is no isolation, but it would only be interesting, if this would work.

[Dr-Gigavolt]

I change my reply, you wrote about VE.direct and I misunderstood it as VE.bus :-)
The VE.direct is described here: https://www.victronenergy.com/live/vedirect_protocol:faq
I don't know if the Louis's driver supports it on the VE.direct. If so, you have the same physical layer. But the isolation is necessary. In te FAQ above yo see, that the genuine Victron VE.direct cables are isolated.

[claib]

sorry : i dont get it -( on my jk-b2a8s20p i've got a RS485, and a GPS port. Using the RS485 port: do you know the assignment of the 3 pins of the RS485 port ? In this case, i just need a RS485 isolated converter to USB like : [image: grafik.png] No need for the JK tiny adapter box ? I've tried with : [image: grafik.png] - but no luck.. perhaps i took the wrong pins... best regards Christoph Am Mi., 12. Okt. 2022 um 07:57 Uhr schrieb Dr-Gigavolt < ***@***.***>:

…

Is the JKBMS RS485 dongle isolated? Please check it. If not, I would not trust in https://www.waveshare.com/product/iot-communication/usb-to-rs485.htm or similar. If the power ground is disconnected by MOSFETs, the battery current will try to flow through the digital ground and it blows something up. — Reply to this email directly, view it on GitHub <#250 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACAIWJLQRZFP33MPSZPHSUDWCZHM7ANCNFSM6AAAAAARCAG4WM> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>

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[Louisvdw]

You must use the GPS port. The CAN/RS485 port will not work for what we are doing. It is not a RS485 port.
See my post just below the pictures for the pin outs and details. I explain both connection options you have

[claib]

thank you so much :-)
can't find th post you mention. Could you give me the link ?

[Louisvdw]

#250 (comment)

[claib]

The 4way TTL to USB Adapter from duppa.net works perfectly. But you have to adapt the 12v positive pin on the jk BMS to 3.3V with a DC DC step down converter. With the 4 way duppa, you have 3 more VE-direct ports for MPPT's or a Shunt from Victron. Cheers Manuel ***@***.***> schrieb am So., 4. Dez. 2022, 22:39:

…

This is very kind of you, but you don't need to. I try to find the best option with less hardware as possible, so less parts can break. I just found this USB to 1x TTL <https://www.duppa.net/shop/isolated-debug-board/> and USB to 4x TTL <https://www.duppa.net/shop/isolated-4-port-usb-to-ttl-uart-ftdi/> adapters which are galvanic isolated through a video <https://www.youtube.com/watch?v=5Tzxd2UQoDM> from Off-Grid-Garage. Now I have another dumb question. This adapter says USB to TTL UART FTDI. So you can use this adapter to connect VE.Direct devices. Should I then also be able to connect the JK BMS RS485 port (which is TTL what I understood now) directly to the VE.Direct port of my MultiPlus II-GX? Obviously in this case there is no isolation, but it would only be interesting, if this would work. — Reply to this email directly, view it on GitHub <#250 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACAIWJP7S5IW2RVUGULHXOLWLUFSRANCNFSM6AAAAAARCAG4WM> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>

[mr-manuel]

Thank you very much.

[alex90alex]

Hi, is it possible to connect the jk bms with rs 485 Adapter from jk with the usb Adapter in the attached picture to the raspberry with Venus OS? When I connect all together I cannot see the bms in the victron portal. Do I need another Adapter? Thank you so much. Alex

[Dr-Gigavolt]

Hi Alex. Your adapter is not RS485, it is serial. It cannot work. You need no RS485 Dongle for it. You can connect it as Louis explained. But it has no isolation, please read my explanation why it is necessary for reliable operation.

[alex90alex]

Hi thanks for your instant help. I ordered a isolated RS485 to USB Adapter. Hopefully it will work fine. Is it possible to check the rs485 Adapter from the jk bms with a Multimeter? Thanks a lot. Alex

[Dr-Gigavolt]

No, you need the other device to communicate. In case of troubles you can check the signals with an oscilloscope, but not with a multimeter.

[claib]

if the coupler is isolated, it needs power from the side from where the signal comes from. JKBMS provides full battery voltage to the + therefore i places a step-down converter between + and the coupler. works fine cheers Christoph Am Mo., 12. Dez. 2022 um 20:06 Uhr schrieb locke981 < ***@***.***>:

…

I have installed the waveshare box now ( https://www.waveshare.com/usb-to-rs232-485-ttl.htm) with no success. I'm getting: @4000000063977940391d50a4 INFO:SerialBattery:Starting dbus-serialbattery @40000000639779403923fbac INFO:SerialBattery:dbus-serialbattery v0.14 @4000000063977940392b1414 INFO:SerialBattery:Testing Jkbms @4000000063977943310df5e4 ERROR:SerialBattery:CRC checksum mismatch: Expected 0x5b6b, Got 0x326f0c @40000000639779441356a154 INFO:SerialBattery:Testing Jkbms @40000000639779463a512d24 ERROR:SerialBattery:CRC checksum mismatch: Expected 0xab6b, Got 0x364549 @40000000639779471caadc0c INFO:SerialBattery:Testing Jkbms @400000006397794a07f54504 ERROR:SerialBattery:CRC checksum mismatch: Expected 0x6dda, Got 0x3882dc I have connected ground, rx and tx on the ttl connector on the adapter and the switch is set to 3.3V. Bat+ is not connected... On the same Raspi I successfully can connect the same BMS to the JK RS485 Adapter so I assume everything is correct on the Raspi itself. I already tried to change the rx/tx cables without success. I never changed ground. What could be the issue here? — Reply to this email directly, view it on GitHub <#250 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACAIWJODCRZJ7KLZSQ4TLL3WM5ZUJANCNFSM6AAAAAARCAG4WM> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>

-- *Christoph Laib* *VIOS GmbH, Switzerland* *Speicherstrasse 27* *CH-9053 Teufen* M: +41 79 600 62 32 E: ***@***.*** ***@***.***> W: www.vios.ch

[Dr-Gigavolt]

Not necessarily. My isolated adaptors have DC/DC converter to transfer the power from the USB.

[Dr-Gigavolt]

Waveshare:
Onboard unibody power supply isolation, provides stable isolated voltage, needs no extra power supply for the isolated terminal

[Greature8]

Good evening mr:s

I really appreciate the community efforts, especially mr. LouisVDW.

I thought with this good documentation i can manage... But nope.. so please, HELP.

I'm runnin 3 multiplus II 48/5000s with 4 DIY 16S 280Ah Lifepo4 batteries, each managed by JKBMS BD6A20S10P.
I have my "CerboGX" on RPi 2.

The problem is I cant get my USB TTL converter to connect. I have done the noobie installation and from the log i suppose it installed OK?

I think the problem might lay within the wire itself, that i had to make. My TTL USB converter is this:
https://www.triopak.fi/fi/tuote/WS-7965
(its in finnish i hope translate works)
I also ordered approppriate connector to fit the BMS end of the cable. Currently i have connected my:
TTL black = BMS GND
TTL green = BMS RX
TTL white = BMS TX
(using the "GPS" port)

(as per this image)

I also tried reversing TX and RX, that made no difference.

Ideas?

[Dr-Gigavolt]

I'm cheering on the idea that because they were at 3.3 volts, the capacity/voltage curve is just so flat around there

Li cells are very flat. They must be full to be not flat and give the chance the balancer to work.

What system you have with that kind of battery config?

Two batteries with 5P x 22S x Yinlong LTO 66160H, 2.3V 40Ah. Unfortunately big LTO cells are not available, must be connected parallel.

[Greature8]

Two batteries with 5P x 22S x Yinlong LTO 66160H, 2.3V 40Ah. Unfortunately big LTO cells are not available, must be connected parallel.

NICE!

I was thinking of building from LTO cells also, but I calculated that the cells would propably outlive me and thus I would not be getting the full advantage from the extra investment. Could you show me some HC pics of your batteries? 🥵

[Dr-Gigavolt]

[Greature8]

Nice, those LTO cells are so hot!

[Greature8]

I GOT IT TO WORK!!!! YESSS EVERYONE!

I just applied the revov fix as suggested, rebooted and BAM I got serialbattery on my device list.
Now I only need to learn how to change the current limits... I need full powaH!!!

[DLAA12]

Hello,

try to get JK-BMS runing on Rpi Venus , by installing like discribed by Loius , I see the following response.
Can someone tell me what I am doing wrong or what the reason is please ??

[Louisvdw]

just reboot youe GX device and it should pick up

[bassmaster187]

If anybody needs a case for the DollaTek USB 2 TTL module, you can download it for free to 3D print it:
https://www.thingiverse.com/thing:6785565

[charlesrg]

Guys, Ive found this USB to TTL adapters:
https://www.aliexpress.us/item/3256806417978404.html
https://www.aliexpress.us/item/3256803438425755.html
https://www.waveshare.com/usb-to-4ch-ttl.htm

They all have 4 ports, I'm wondering if they could be used to connect multiple B2A8S20P to a single USB port on the CerboGX.

@Dr-Gigavolt mentioned about isolation on RS485, would that be also necessary for TTL ?
@mr-manuel are you using the 4 channel TTL to USB adapter ?

[Dr-Gigavolt]

I already answered the question. The wiring as well as Mr Manuel are right. The DC/ DC adapter is on board. About fried adapter ... RTFM or use multimeter. The VCC on BMS is the full battery voltage. And the RS485 is not implemented directly on the BMS. A JK RS485 Adapter is needed.

[mhin76]

Hi Dr. Gigavolt. I think I misunderstood that DC/DC adapter (lessons learned now :-)). And yes, I measured the voltage, 58V, no wonder the adapter got fried. Now I FINALLY GOT CONNECTION!!! with another adapter I tried before without success. I just played around with my JK BMS settings and chose the first entry "000 - 4G-GPS Remote module Com..." instead of the one that I chose so far "001 - JK BMS RS485 Modbus V1.0". To my surprise now with the 000 setting I got the connection! :) Will order another isolated adapter now ;-)

I hope, I did not miss that somewhere as well ;-)

[Albarge]

This was a great thread I used for info when setting up my system last year, but now I'm thinking to try and get the RS485 daisy chained from each battery, I have 2023 JK BMS's with the option to set Device address, I'm still running Serial battery 1.2.20240401 I guess I may need to update?

I have 3 x JK B2A8S20P, 3 x JK TTL>RS485 and 3 x Waveshare isolated USB to RS485

I'm hoping to daisy chain the RS485 so I can just use a single Waveshare USB to RS485 as the Cerbo has always been on the limit of processor power and maybe a single USB to RS485 will help?

But, I read @Dr-Gigavolt advice and only connected A, B. I didn't connect the common GND, or the shield (Only 1m distance), it has worked for the last year like this, but reading the updated https://mr-manuel.github.io/venus-os_dbus-serialbattery_docs/general/connect#rs485modbus-daisy-chain-possible I see it is recommended to connect GND.

If the JK BMS with the TTL-RS485 adaptor is plugged into the GPS port can they get damaged if one BMS opens the negative, will current try to flow through the common GND to the others in the daisy chain? Or is it OK for the BMS's? The Cerbo is behind the Isolated Waveshare so should be good?

If I should still not connect the GND maybe there should be a note in the docs for other JK users about that?

Also great to see the improved documentation from @mr-manuel but I think the description of the diagrams is wrong under https://mr-manuel.github.io/venus-os_dbus-serialbattery_docs/general/connect#uartttl-no-daisy-chain-possible it says "Connect the wires in a point-to-point configuration" but then shows a diagram of a crossover cable?

[mr-manuel]

I'm hoping to daisy chain the RS485 so I can just use a single Waveshare USB to RS485 as the Cerbo has always been on the limit of processor power and maybe a single USB to RS485 will help?

Not really, since the same data is processed, maybe a bit slower. In the FAQ you can find how to reduce CPU load.

To be sure with the GND, measure the resistance.

Point-to-point --> Device-to-device. I changed it.

[Dr-Gigavolt]

The interconnection between multiple Multiplus or Quattro is made with UTP cables, without ground. This avoids ground loops. I would also never build such ground loops through BMS. Differential and isolated signals don't need ground at all.

[mhin76]

Hi all
I am about to get nuts. I had my system working finally with my JK BMS JK-B2A24S15P (I know, not exactly the one mentioned in the title, but maybe similar behavior) and Venus OS on my Raspberry Pi 3 via a USB-TTL adapter. Worked find until I shut the system down to take a backup of the SD card. After rebooting the dbus-serial-battery adapter is not fining the battery anymore. :'-( I have not changed any settings on my JK. I see that the driver is sending commands but nothing comes back. I had the same behavior month before it finally got working.
I did not touch anything on JK side and settings are still the same (UART protocol set to GPS).

Did anyone of you discover such instability with a JK BMS via RS485?
On the driver log I just see message "ERROR: no reply - returning"

I am using dbus-serialbattery v1.5.20241215

here well seen the log when it worked. after reboot the driver is just not doing anything at all anymore. after googling I found one issue was that the serial driver was taken (see #675). Now at least it iterates again over USB2 where my TTL adapter is connected, but it does not find the JK anymore.

Here the log, when it found it successfully:

root@raspberrypi2:/data/etc/dbus-serialbattery# tail -n 100 -f /data/log/dbus-serialbattery.ttyUSB2/current | tai64nlocal
2024-12-08 15:20:32.570037500 INFO:SerialBattery:Starting dbus-serialbattery
2024-12-08 15:20:32.572511500 INFO:SerialBattery:Venus OS v3.52 running on Raspberry Pi 3 Model B Rev 1.2
2024-12-08 15:20:32.573588500 INFO:SerialBattery:dbus-serialbattery v1.5.20241202
2024-12-08 15:20:48.591216500 INFO:SerialBattery:-- Testing BMS: 1 of 3 rounds
2024-12-08 15:20:48.591223500 INFO:SerialBattery:Testing Jkbms
2024-12-08 15:20:48.737902500 INFO:SerialBattery:-- Connection established to Jkbms
2024-12-08 15:20:49.768644500 INFO:SerialBattery:Reconnected to previously identified battery with DeviceInstance: 2
2024-12-08 15:20:50.040956500 INFO:SerialBattery:Use DeviceInstance: 2
2024-12-08 15:20:50.042268500 INFO:SerialBattery:Use dbus ServiceName: com.victronenergy.battery.ttyUSB2
2024-12-08 15:20:50.094865500 INFO:SerialBattery:Polling interval: 1.000 s
2024-12-08 15:20:50.096962500 INFO:SerialBattery:Battery JKBMS connected to dbus from /dev/ttyUSB2
2024-12-08 15:20:50.098222500 INFO:SerialBattery:========== Settings ==========
2024-12-08 15:20:50.099120500 INFO:SerialBattery:> Connection voltage: 58.95 V | Current: -0.0 A | SoC: 5%
2024-12-08 15:20:50.099891500 INFO:SerialBattery:> Cell count: 18 | Cells populated: 18
2024-12-08 15:20:50.100661500 INFO:SerialBattery:> LINEAR LIMITATION ENABLE: True
2024-12-08 15:20:50.101525500 INFO:SerialBattery:> MIN CELL VOLTAGE: 2.900 V | MAX CELL VOLTAGE: 3.450 V| FLOAT CELL VOLTAGE: 3.375 V
2024-12-08 15:20:50.102210500 INFO:SerialBattery:> MAX BATTERY CHARGE CURRENT: 80.0 A | MAX BATTERY DISCHARGE CURRENT: 80.0 A
2024-12-08 15:20:50.103022500 INFO:SerialBattery:> MAX BATTERY CHARGE CURRENT: 60.0 A | MAX BATTERY DISCHARGE CURRENT: 100.0 A (read from BMS)
2024-12-08 15:20:50.103740500 INFO:SerialBattery:> CVCM:     True
2024-12-08 15:20:50.104323500 INFO:SerialBattery:> CCCM CV:  True  | DCCM CV:  True
2024-12-08 15:20:50.104902500 INFO:SerialBattery:> CCCM T:   True  | DCCM T:   True
2024-12-08 15:20:50.105517500 INFO:SerialBattery:> CCCM SOC: False | DCCM SOC: False
2024-12-08 15:20:50.106063500 INFO:SerialBattery:> CHARGE FET: True | DISCHARGE FET: True | BALANCE FET: True
2024-12-08 15:20:50.106589500 INFO:SerialBattery:Serial Number/Unique Identifier: 407052E0472
2024-12-15 09:19:28.203099500 *** CCGX booted (0) ***

Now the log:

2024-12-16 06:56:22.115826500 INFO:SerialBattery:Starting dbus-serialbattery
2024-12-16 06:56:22.117876500 INFO:SerialBattery:Venus OS v3.52 running on Raspberry Pi 3 Model B Rev 1.2
2024-12-16 06:56:22.118310500 INFO:SerialBattery:dbus-serialbattery v1.5.20241215
2024-12-16 06:56:38.135279500 INFO:SerialBattery:-- Testing BMS: 1 of 3 rounds
2024-12-16 06:56:38.135826500 INFO:SerialBattery:Testing Jkbms
2024-12-16 06:56:38.410466500 ERROR:SerialBattery:>>> ERROR: No reply - returning
2024-12-16 06:56:38.912381500 INFO:SerialBattery:-- Testing BMS: 2 of 3 rounds
2024-12-16 06:56:38.912835500 INFO:SerialBattery:Testing Jkbms
2024-12-16 06:56:39.185449500 ERROR:SerialBattery:>>> ERROR: No reply - returning
2024-12-16 06:56:39.687187500 INFO:SerialBattery:-- Testing BMS: 3 of 3 rounds
2024-12-16 06:56:39.687645500 INFO:SerialBattery:Testing Jkbms
2024-12-16 06:56:39.959142500 ERROR:SerialBattery:>>> ERROR: No reply - returning
2024-12-16 06:56:40.460891500 ERROR:SerialBattery:ERROR >>> No battery connection at /dev/ttyUSB2

[mhin76]

I will create a dedicated discussion thread with my type of JK BMS, not it got more urgent bc the bluetooth solution got very instable, drops connection after few minutes and only reconnects after restart. might be related with #655 . Maybe someone in the community has a similar behavior.

[mhin76]

Update: not sure what exactly happened but now it works again via TTL!! (not going to reboot my running system now ;-)). Would like to share some steps I did, maybe it helps others.

• by BLE connection was very very unstable (more than usually)
• so I tried again via TTL (I disabled the bluetooth row in config.ini) -> nothing
• I used following command from Bluetooth connection disrupted #655: echo "sbattery" > /data/var/lib/serial-starter/ttyUSB2 (TTL adapter connects to USB2, at least that is where it worked before) -> nothing
• I tried command rm /data/var/lib/serial-starter/* also from Bluetooth connection disrupted #655 -> nothing
• just by chance I disabled in config.ini that it should ignore USB0, as bluetooth was connected to USB0
  ; EXCLUDED_DEVICES = /dev/ttyUSB0
• next time I checked at the driver it worked and was connected to USB0!! no idea why, I did not change the port, but it works. maybe the rm command above reset the order of the USB ports.

if you have the same JK BMS and encounter trouble, let me know!! I can send you all settings (also JK BMS settings, even they are not intuitive!)

and thank you all for your feedback on my other hurdles! much appreciated!

[Dr-Gigavolt]

Martin, IMHO the best you can do is to use serial TTL or RS485 with good hardware. Battery management is a safety relevant process, BT is not designed for this purpose. Radio communication can get interfered, cable not. You should concern the BMS MOSFET disconnect as the ultima ratio, not as a replacement for non reliable operation of battery driver. Because BMS can fail as well and if you rely only on it, the risk of fire desaster increases significantly. You have to keep both systems as reliable as possible.

[mhin76]

Gigavolt, I fully agree with you. That is why I wanted to switch from BL to cable. But JK BMS settings are very contradicting and not sure what I did wrong with the driver and the ports. But now it is working! :-)
at least before via BL when BMS was disconnected the MultiPlus stopped charging/discharging.

[Raspb-henk]

Hi
A detail question but I donot want to damage anything.
I have a jk bms b2a8s20p and just received the appropiate jk 485 dongle to plug into the gps port of the bms. I want to use the Duppa 4 isolated connector to connect to the usb port of a Rpi. I read that I have to use a dc dc convertor to lower the voltage to3.3V.
How do I connect the dc dc? I think i connect the plus to the red lead going to the rs485 (12v)and the output (3.3v) to the plus off the Duppa? So the 485 dongle keeps 12v.?
Must I also make a seperate minus lead direct from the dc dc to the minus of the Duppa or do I connect the minus of the dc dc to the black lead between the gps port and the 485 dongle?

[mhin76]

Hi Raspb-henk

Is the Duppa 4 a USB to RS485 and not to TTL?
I use an isolated connector USB-to-TTL-Serial (https://de.aliexpress.com/item/1005006295605881.html?spm=a2g0o.order_list.order_list_main.135.24d35c5fSov57s&gatewayAdapt=glo2deu) without the JK 485 dongle (not required). Maybe on your isolated Duppa 4 connector there is a DC-to-DC converter already, means you do not have to feed voltage on the 485 side.
Important is the setting on your JK (at least for my set-up), see my experience above.
let me know if you struggle, as you have quite similar set-up as I have
Kind regards, Martin

[Raspb-henk]

Hi
I have this : https://www.mttec.de/Duppa-Isolated-4-port-USB-to-TTL-UART-FTDI-JST-XH As far as I know it has no DC to DC convertor on board. I have understood that I must use a seperate DC to DC to add 3.3v input to it.

[Louisvdw]

@Raspb-henk you cannot use the duppa and the jk 485 dongle. They are different standards (TTL vs RS485)
see #250 (comment)

If you don't use the 485 dongle then you can use the Rx/Tx from the GPS port, but you need to supply it with 5V power (not using the BMS Vcc). The Duppa is Isolated. This means it need power (the 5V) to be supplied to both the in side and the out side) as no power flow from the in side to the out side.

[Raspb-henk]

Ok so i do not use the jk 485. Then this is the correct way (with 5v and not 3.3v)

[mhin76]

how many cells do you have on your battery pack? e.g. I have 18 cells, means the voltage on JK BMS GPS connector is 60V!