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JK 4S 200A BMS

PS, I'm just a shmuck who wrote / rewrote BMS Manuals, Instructions & Docs, as well as Battery Assembly guides, some of which have resource links to the specific bits related... But What do I KNOW ?
I meant no offense and am well aware of all the work you have done and appreciate it :). When I meant "verification" it was because the JK BMS indicates that it tracks the resistance of each lead and therefore I had an assumption that it can compensate for different resistance. Otherwise what is the point of displaying cell wire resistance on the main screen (asking in a curious manner).
 
I did just check what it shows for my cell wire resistance and the two shortest leads (cell 1 and cell 16) are the two with the lowest cell wire resistance so it seems to be indicating that correctly. Would that mean it is okay to have the different lengths? I've had issues with several cells drifting from others and as experiment I cleaned terminal of one and it immediately fixed it so not related to leads. This is on a 48V battery.
 
 
The length of the balance cable is 75-80cm by default If the customer needs to extend these cables, our recommendation is not to exceed 130cm, otherwise the voltage acquisition accuracy will be affected, which will cause the BMS performance to be unstable
 
The length of the balance cable is 75-80cm by default If the customer needs to extend these cables, our recommendation is not to exceed 130cm, otherwise the voltage acquisition accuracy will be affected, which will cause the BMS performance to be unstable
This should also be added to the new version of the User Manual.
Additionally that if they shorten them, is best to still keep them at the same length, or how to correct for the varying resistance values.
 
The length of the balance cable is 75-80cm by default If the customer needs to extend these cables, our recommendation is not to exceed 130cm, otherwise the voltage acquisition accuracy will be affected, which will cause the BMS performance to be unstable
The question is this: Is it OK to cut the individual BMS sense wires to different lengths?

@Nami


(I did this, to clean up the installation)
There are "settable" wire resistance values on the settings tab of the app, what is the purpose of these? Thanks
 
Cables are made to a length that does not exceed the range (<130cm) and will not affect the accuracy of voltage collection.
If the batteries are connected in parallel. Then connect a BMS,
For example, the three-dimensional battery of an electric motorcycle,
Usually 13S7p or 17S6P is used (based on the usage of electric motorcycles in China).
At this point the loss value of the cable is calculated to compensate for.
This part of the value is calculated based on the customer's battery resistance.
It is more complex.
The question is this: Is it OK to cut the individual BMS sense wires to different lengths?

@Nami


(I did this, to clean up the installation)
There are "settable" wire resistance values on the settings tab of the app, what is the purpose of these? Thanks
 
Cables are made to a length that does not exceed the range (<130cm) and will not affect the accuracy of voltage collection.
If the batteries are connected in parallel. Then connect a BMS,
For example, the three-dimensional battery of an electric motorcycle,
Usually 13S7p or 17S6P is used (based on the usage of electric motorcycles in China).
At this point the loss value of the cable is calculated to compensate for.
This part of the value is calculated based on the customer's battery resistance.
It is more complex.
Please be clear. YES it is OK to have various length BMS wires? or NO?
 
Obviously @Nami knows better than me, but I would not want my BMS sense wires to be very different in length. Different lengths mean different resistance. If the sense cables were literally only sensing (no current), then it wouldn't matter. But with up to 2A of balance current it seems to me that the difference in lengths will translate to the same voltages at the cells being measured as different at the BMS. Unless I'm missing something. Am I wrong?
 
Obviously @Nami knows better than me, but I would not want my BMS sense wires to be very different in length. Different lengths mean different resistance. If the sense cables were literally only sensing (no current), then it wouldn't matter. But with up to 2A of balance current it seems to me that the difference in lengths will translate to the same voltages at the cells being measured as different at the BMS. Unless I'm missing something. Am I wrong?
That is exactly the reason that they calculate the resistance and show that value on the app. @RCinFLA goes into great detail on the system in the link in post #263 above. From everything I have seen, it is a bad idea to have different length of sense wires in any BMS except for the JK BMS
BUT, because of the fact that JK measures the actual resistance and makes the needed adjustments to the balance current, it does not matter on the JK unless you go over 130cm.
 
That is exactly the reason that they calculate the resistance and show that value on the app. @RCinFLA goes into great detail on the system in the link in post #263 above. From everything I have seen, it is a bad idea to have different length of sense wires in any BMS except for the JK BMS
BUT, because of the fact that JK measures the actual resistance and makes the needed adjustments to the balance current, it does not matter on the JK unless you go over 130cm.
Ahh! Thanks for that!

I was away and off the forum for over a month, so I have missed and continue to miss some things. I guess I knew that the JK had wire resistance, but didn't know how the numbers got in there. @RCinFLA has it all making sense now.
 
Ahh! Thanks for that!

I was away and off the forum for over a month, so I have missed and continue to miss some things. I guess I knew that the JK had wire resistance, but didn't know how the numbers got in there. @RCinFLA has it all making sense now.
I had asked several JK users if they had used a meter to find the resistance of the wires and was always told that the values were created by the BMS so it seemed that this was being done which is why I asked the question. If the length does not mater (because the BMS is adjusting itself for the resistance of each wire) then I can cut them to length to get the neatest installation.
 
My BMS showed up today.
Unfortunately, the cover plate / heat sink was pretty mangled in shipping. Two of the mounting ears were bent with one almost 180º. Both the top and bottom plate are also bent outward between the case screws which seems to indicate that the FETs have probably been crushed somewhat.

Compared to the packaging that we get with the cells this was very weak. It was in a thin bubble wrap bag inside of a single layer cardboard box with the loose bits packed down around it. I have received $20 electronics that were packaged in solid boxes with form fitting foam over an inch thick inside. I expected better packaging than this.
 

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Not even sure form fitting foam would have saved that.. That had to have been a lot of weight on it to bend like that.
 
I also received my pair of the B2A8S20P-H BMSes and a pair of the 4.5" LCDs today. Each component was in its own box packed with minimal bubble wrap and then all 4 boxes were in an overpack box with no additional packing material. There was no shipping damage to anything thankfully but the packing seemed barely adequate.
I now realize that it was not clearly indicated WHAT was included in the 4.5" display kit that was specific for the B2A8S20P. The RS-485 adapter was NOT included as I expected. The LCD/switch cable that was included is only about 12" long which is functionally worthless as NO one would install the 4.5" display within a foot of the BMS. Also most of the printed port labels on both the BMSes are illegible (not a big deal but still...) . So now I have to wait another two months for the RS485 adapters. In the meantime, I will need to extend the LCD cable to a usable length.
 
I also received my pair of the B2A8S20P-H BMSes and a pair of the 4.5" LCDs today. Each component was in its own box packed with minimal bubble wrap and then all 4 boxes were in an overpack box with no additional packing material. There was no shipping damage to anything thankfully but the packing seemed barely adequate.
I now realize that it was not clearly indicated WHAT was included in the 4.5" display kit that was specific for the B2A8S20P. The RS-485 adapter was NOT included as I expected. The LCD/switch cable that was included is only about 12" long which is functionally worthless as NO one would install the 4.5" display within a foot of the BMS. Also most of the printed port labels on both the BMSes are illegible (not a big deal but still...) . So now I have to wait another two months for the RS485 adapters. In the meantime, I will need to extend the LCD cable to a usable length.
I have been in contact this evening with Hankzor regarding the interconnection between the B2A8S20P BMS and the 4.5" LCD display and they have clarified that what is stated on their webpage does NOT apply in this situation and the RS485 port is NOT used in any manner with this display AND the RS485 port remains open to be used for other purposes at the same time as the 4.5" LCD is connected. They have indicated that the webpage will be corrected.
 
My BMS showed up today.
Unfortunately, the cover plate / heat sink was pretty mangled in shipping. Two of the mounting ears were bent with one almost 180º. Both the top and bottom plate are also bent outward between the case screws which seems to indicate that the FETs have probably been crushed somewhat.

Compared to the packaging that we get with the cells this was very weak. It was in a thin bubble wrap bag inside of a single layer cardboard box with the loose bits packed down around it. I have received $20 electronics that were packaged in solid boxes with form fitting foam over an inch thick inside. I expected better packaging than this.
We will improve the packaging of the goods, but such damage is obviously the responsibility of the courier. Please test it as soon as possible. If the BMS cannot be used, we will refund it for you. We will contact the logistics provider for compensation. Thank you for your support
 
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