JK-B2A8S20 BMS Variants

[packrat1969]

Hello,

Is there someone out there that can help me clarify a couple of issues regarding the JK-B2A8S20 series of BMS'? It seems that not a single vendor on Alibaba or AliExpress can reliably list the specific model number with it's included feature set for this line of BMS'. The manufacturer doesn't even have a printed English manual specific to this BMS listing each variant but only mentions them in passing. I found Steve_S' revised version, but it only had the same vague chart. All in all, this makes it rather confusing to determine just what version is being offered when ordering. I also don't see a generic UART version, so I suspect I'll need to order one of the RS-485 versions along with the appropriate RS-485-to-USB adapters. Below is an incomplete listing of what I suspect are the model's variants, so feel free to correct any inaccuracies or misunderstandings I have:

JK-BMS-B2A8S20P (Bluetooth, RS-485)
JK-BMS-B2A8S20P-H ((Bluetooth, RS-485, Heating Relay Port) I have yet to see this model explicitly listed.
JK-BMS-B2A8S20C ((Bluetooth, CAN Interface)
JK-BMS-B2A8S20C-H ((Bluetooth, CAN Interface, Heating Relay Port)

I am currently using a JBD-SP04S028A 150A BMS, but it has some communications and balancing current limitations I'd like to forego by replacing it with the JK unit. First off, it has only one RS-485 port that can be used with EITHER an external Bluetooth module OR an external UART-to-USB adapter box. They both work great, however the both use the same 4-pin port. The UART-to-USB arrangement seems to work well with all my Victron hardware (Cerbo, MPPT, & Shunt) using Louis Van Der Walt's dbus-serialbattery driver, but this means that every time I want to tweak the BMS settings, I need to disconnect the USB communication path in favor of the Bluetooth one I can use with my phone. I'm probably not the only one who hates the PC software. Currently I have a multi-pole switch that can do this properly, but what I really want is the option to connect to the BMS with Bluetooth and UART/RS-485 simultaneously. From what information I've witnessed so far, it seems that models in this series of JK BMS' have Bluetooth built into the main board, eliminating the need for an external UART-fed Bluetooth module. Can someone confirm this?

Additionally, the JBD unit only balances with something like 70mA (??), and cannot keep up with the runners in my Basen "Grade A" 280Ah 4S pack at the end of a charge cycle. I wonder if 2A of balancing current stripped from the misbehaving cells and sent to their brethren might do the trick.

Now, as far as connecting this BMS to something like a Cerbo GX, the unit's documentation appears to be seriously lacking. I see there is a port on the BMS labeled RS-485, but will it communicate properly with one of these?


It does not appear to come with a harness ending in the proper connector to plug into the RS-485 port. This I can remedy if necessary. Below is a link to one on AliExpress: RS-485 to USB

https://www.aliexpress.us/item/3256...vfUNAJxZ&utparam-url=scene:search|query_from:


I have also seen one of these being sold with/for these BMS'. It looks like some kind of external RS-485 conversion dongle, that has a (3-conductor???) connector that plugs into something on the BMS while the wires exiting the other end terminate in (2) bare conductors. I thought RS-485 was already generated onboard the BMS, and I would just need to to convert its serial protocol to USB. What is the purpose of this item? RS-485-to-CAN?


Here's a link to one:

https://www.aliexpress.us/item/3256805022503564.html?spm=a2g0o.productlist.main.9.775b7bddQ96tv3&algo_pvid=e4c841f5-486c-4d82-a2c9-96e62390a60f&algo_exp_id=e4c841f5-486c-4d82-a2c9-96e62390a60f-4&pdp_npi=4%40dis%21USD%2111.45%219.16%21%21%2111.45%219.16%21%402101c71a17204520343637887e0b5e%2112000032181768522%21sea%21US%210%21AB&curPageLogUid=UxkGvfUNAJxZ&utparam-url=scene%3Asearch%7Cquery_from%3A

Any relevant directions/comments appreciated.

packrat

 

[chrisski]

I recently installed a JK BMS on a 8S 24 volt build. I felt I was the first person to ever build one. It took me hours to configure. To turn it on you not only have to attach it, but put a powersupply over the leads for a few seconds until it starts to beep and then wait until it stops beeping. What a perfect thing you'd think would be in the documentation.

First off, it has only one RS-485 port that can be used with EITHER an external Bluetooth module OR an external UART-to-USB adapter box.

Mine had a built in Blue Tooth that did not take a UART adapter like My OverKill/JBD unit did. It also has a RS-485 port, and whether this works at the same time as bluetooth or not, if one does not know how to read Chinese, you need to buy it and try it to find out.

Looking at the documentation it looks like a V11 has one and a V15 may have two. My box in no way had any partnumber on it other than the JK-BMSB620S6P and I think I got a V11 because it only had one picture.

I see there is a port on the BMS labeled RS-485, but will it communicate properly with one of these?

Unfortunately, I don't know and hope you find out, but I have resigned myself that you to buy it to find out.

Additionally, the JBD unit only balances with something like 70mA (??), and cannot keep up with the runners in my Basen "Grade A" 280Ah 4S pack at the end of a charge cycle. I wonder if 2A of balancing current stripped from the misbehaving cells and sent to their brethren might do the trick.

JK-BMS-B2A8S20P (Bluetooth, RS-485)

As far as I can tell, This stands For Balance 2 amps ; 8S setup; 20 in parallel can be viewed on software or app.

I recently bought and installed a JK-BMSB620S6P unit.
This came with .6 amps balancing, Up to 20S capable (I set up to 8S), and up to 6 BMSs viewable.

I found nothing else to tell me what a part number is. What looks like a part number does not tell (JK-BMSB620S6P) me if its a V11 or V15 or if it has the LED display or an on/off button.

 

[Zwy]

Hello,

Is there someone out there that can help me clarify a couple of issues regarding the JK-B2A8S20 series of BMS'? It seems that not a single vendor on Alibaba or AliExpress can reliably list the specific model number with it's included feature set for this line of BMS'. The manufacturer doesn't even have a printed English manual specific to this BMS listing each variant but only mentions them in passing. I found Steve_S' revised version, but it only had the same vague chart. All in all, this makes it rather confusing to determine just what version is being offered when ordering. I also don't see a generic UART version, so I suspect I'll need to order one of the RS-485 versions along with the appropriate RS-485-to-USB adapters. Below is an incomplete listing of what I suspect are the model's variants, so feel free to correct any inaccuracies or misunderstandings I have:

JK-BMS-B2A8S20P (Bluetooth, RS-485)

This is the model I use, 2A active balancing, bluetooth built in and the RS485 allows for use of a screen. I mentioned the one I use in this thread.

JK-BMS-B2A8S20P-H ((Bluetooth, RS-485, Heating Relay Port) I have yet to see this model explicitly listed.

Same internals, just has a port to control a heat pad.

JK-BMS-B2A8S20C ((Bluetooth, CAN Interface)
JK-BMS-B2A8S20C-H ((Bluetooth, CAN Interface, Heating Relay Port)

Both used if you want CAN communication with an inverter.

I am currently using a JBD-SP04S028A 150A BMS, but it has some communications and balancing current limitations I'd like to forego by replacing it with the JK unit. First off, it has only one RS-485 port that can be used with EITHER an external Bluetooth module OR an external UART-to-USB adapter box. They both work great, however the both use the same 4-pin port. The UART-to-USB arrangement seems to work well with all my Victron hardware (Cerbo, MPPT, & Shunt) using Louis Van Der Walt's dbus-serialbattery driver, but this means that every time I want to tweak the BMS settings, I need to disconnect the USB communication path in favor of the Bluetooth one I can use with my phone. I'm probably not the only one who hates the PC software. Currently I have a multi-pole switch that can do this properly, but what I really want is the option to connect to the BMS with Bluetooth and UART/RS-485 simultaneously. From what information I've witnessed so far, it seems that models in this series of JK BMS' have Bluetooth built into the main board, eliminating the need for an external UART-fed Bluetooth module. Can someone confirm this?

Additionally, the JBD unit only balances with something like 70mA (??), and cannot keep up with the runners in my Basen "Grade A" 280Ah 4S pack at the end of a charge cycle. I wonder if 2A of balancing current stripped from the misbehaving cells and sent to their brethren might do the trick.

I'd break down the pack and top balance the cells first. Cells in parallel, use a power supply set at 3.6V to 3.65V until current drops to about 0A.

Then see how the cells hold balance.

Now, as far as connecting this BMS to something like a Cerbo GX, the unit's documentation appears to be seriously lacking. I see there is a port on the BMS labeled RS-485, but will it communicate properly with one of these?
View attachment 227259

It does not appear to come with a harness ending in the proper connector to plug into the RS-485 port. This I can remedy if necessary. Below is a link to one on AliExpress: RS-485 to USB

https://www.aliexpress.us/item/3256805022503564.html?spm=a2g0o.productlist.main.9.775b7bddQ96tv3&algo_pvid=e4c841f5-486c-4d82-a2c9-96e62390a60f&algo_exp_id=e4c841f5-486c-4d82-a2c9-96e62390a60f-4&pdp_npi=4@dis!USD!11.45!9.16!!!11.45!9.16!@2101c71a17204520343637887e0b5e!12000032181768522!sea!US!0!AB&curPageLogUid=UxkGvfUNAJxZ&utparam-url=scene:search|query_from:


I have also seen one of these being sold with/for these BMS'. It looks like some kind of external RS-485 conversion dongle, that has a (3-conductor???) connector that plugs into something on the BMS while the wires exiting the other end terminate in (2) bare conductors. I thought RS-485 was already generated onboard the BMS, and I would just need to to convert its serial protocol to USB. What is the purpose of this item? RS-485-to-CAN?
View attachment 227258

Here's a link to one:

https://www.aliexpress.us/item/3256805022503564.html?spm=a2g0o.productlist.main.9.775b7bddQ96tv3&algo_pvid=e4c841f5-486c-4d82-a2c9-96e62390a60f&algo_exp_id=e4c841f5-486c-4d82-a2c9-96e62390a60f-4&pdp_npi=4%40dis%21USD%2111.45%219.16%21%21%2111.45%219.16%21%402101c71a17204520343637887e0b5e%2112000032181768522%21sea%21US%210%21AB&curPageLogUid=UxkGvfUNAJxZ&utparam-url=scene%3Asearch%7Cquery_from%3A

Any relevant directions/comments appreciated.

packrat

@timselectric uses this for communication to SA using the JK module https://diysolarforum.com/threads/jk-bms-deal-aliexpress.72147/post-968564 and allows all BMS's to upload SOC to SA.

 

[GuyG]

As far as I can tell, This stands For Balance 2 amps ; 8S setup; 20 in parallel can be viewed on software or app.

20 is not a reference to the number that can be paralleled. It’s an indication that the bms is rated to handle 200 amps of current. 15 stands for 150 amps, 10 stands for 100 amps, etc.

 

[Zwy]

 

[packrat1969]

Thank you for all the replies. They have been helpful, but more info/recommendations are welcome. I guess overall, the largest issue here is the lack of English documentation for this specific series of JK BMS'. Block diagrams that show just what hardware is needed to get the necessary data out of the units would help. Wiring diagrams showing things in more detail would help even more. Neither the manufacturer nor a single vendor seem to understand that the more we know about their products the more we are likely to use them.

@Zwy's breakdown of the model number format breakdown confirms what I already understood. My concern with the model variants was that the vendors seem to play fast and loose with the text descriptions while quoting the model numbers. At the least, this just muddies the water, while at other times they completely contradict themselves. I will avoid those vendors. As for vendors, does anyone have any recommendations? Looking for timely US delivery and possible after-sales support. AliExpress probably doesn't fit that criteria.

As for the 4s battery pack in question, it has been top-balanced several times, but always drifts during partial charges. The (4) cells I ordered from Basen in the fall of 2022 were touted to be CATL 304Ah, but only measured around 278Ah when load tested. Basen also lied to me about the BMS units too. I paid for JBD 200A units, but received only 150A units with what appears to be beta firmware. Apparently this is how business is done in China. I can't say it's all bad though. I went from (2) 6-year old, 6V 225Ah T105 golf cart batteries to a single 12V battery that weighs half as much and lasts 3 times as long and learned a lot along the way.

 

[chrisski]

View attachment 227440

The green should be # of BMS in parallel.

My BMS ends in 6p and is 60 amps

 

[Zwy]

The green should be # of BMS in parallel.

No, it isn't that I am aware of. Do you have documentation for this?

My BMS ends in 6p and is 60 amps

6P would be rated at 60A. 20P is rated at 200A.

 

[GuyG]

The green should be # of BMS in parallel.

It’s not. In fact, that series of bms has no limit on the number that can run in parallel. It has no DIP switches for addressing, as in the jk inverter bms models (which are limited in number that can parallel).

This is the list of models in your bms series:


Edit: Oops, that is the model list for 48-volt bms series. I don’t have one for the 24-volt. But they will be mostly the same except they’ll have 8S instead of 20S or 24S.

 

[chrisski]

No, it isn't that I am aware of. Do you have documentation for this?



6P would be rated at 60A. 20P is rated at 200A.

No documentation. Simply wrong in my understanding.

Thanks for helping me decode this.

 

[packrat1969]

@Zwy and Others,

Regarding the JK BMS units with the active balance function, are Bluetooth and RS-485 on ALL of the boards? When the CAN communication option is chosen during the ordering process, does it replace the RS-485 or is it just an additional communications option? Even the language in the image below is unclear. It's probably just a symptom of the horrible Chinese-to-English translations so prevalent in all of the hardware sales sites, but they sure do like to use the phrase "Need Customization" a lot, with little to no explanation. One would think that if they're selling the things, they would want to clarify just what exactly they are selling.

I also found this to clarify the model number scheme:

 

[Zwy]

@Zwy and Others,

Regarding the JK BMS units with the active balance function, are Bluetooth and RS-485 on ALL of the boards? When the CAN communication option is chosen during the ordering process, does it replace the RS-485 or is it just an additional communications option? Even the language in the image below is unclear. It's probably just a symptom of the horrible Chinese-to-English translations so prevalent in all of the hardware sales sites, but they sure do like to use the phrase "Need Customization" a lot, with little to no explanation. One would think that if they're selling the things, they would want to clarify just what exactly they are selling.

I also found this to clarify the model number scheme:
View attachment 227837

Take a look at the photo in this post. The port is CAN/RS485, it would depend on the cable you plug into it from my understanding. I didn't need CAN so I never looked into it. I do have a cable plugged into that port, the cable came with the screen.

 

[Ed.Kok]

@Zwy That photo is of a different model. It is the ‘inverter’ variant.

This topic was going in the right direction to answer my question, but in the end it didn’t. My question is, if I buy the ‘C’ variant with the CAN-bus, will it still be possible to use it with RS485? Looking at a B2A8S20P-C.
At first I want to connect it with a converter to USB with a raspberry with VenusOS. But later maybe directly to a MultiPlus.