Help with buying a BMS (and believing A.I.)

[Bonwit]

I’m finding I don’t understand everything I know about BMSs! In looking for a suitable 60 amp Smart BMS for my 52v 14S4P pack build, I ended up purchasing a JBD-DB24SA03 unit off Amazon. When I finally received it, the markings and terminal connections were not what I was expecting, and of course there were no instructions or wiring diagrams. In the process of consulting A.I. to sort this all out, I learned that this BMS is a “Same Port” type where the device only controls the negative side of the circuit. I read that there are some advantages and disadvantages to this style, but when A.I. learned that I was planning to only connect 14 of the possible 24 balance wires, it was adamant that this was an unwise configuration, and somewhat of a marketing scam (I assume it picked this up from forum discussions). I see that there are many (most) BMSs on Amazon and Alli that advertise compatibility with a range of series connections, and the wiring diagrams shown in their listings detail simply leaving unused wires disconnected. In addition, advertised voltage ranges vary as well. Is the idea that being a smart BMS, these parameters are configured in the app? Or should I heed A.I. and look for a BMS made for the exact number of series connections? I am having trouble finding a pure 14S BMS that can handle 60 amps. 50 is the highest I’ve seen. Any suggestions?

 

[neptronix]

What you need is not AI but a part with documentation and specifications, made by a company that supports their product.

I would look at any website other than aliexpress and amazon to find these parts, and if the company's webpage doesn't list specs, and the seller doesn't have a manual, don't buy it.

There's a lot of threads about JBD BMSes on this forum if you use the search function and hit the google button for better results.

 

[amberwolf]

I ended up purchasing a JBD-DB24SA03 unit off Amazon. When I finally received it, the markings and terminal connections were not what I was expecting, and of course there were no instructions or wiring diagrams.

You can get the documentation from the manufacturer website, which can be quickly found with a general websearch:
https://www.google.com/search?q=jbd+bms
or one specifically for your model (which shows the documentation in the second link for the results I get here)
https://www.google.com/search?q=JBD-DB24SA03

I'm surprised the AI didn't point you there, since you have the exact model of BMS, etc.

In the process of consulting A.I. to sort this all out, I learned that this BMS is a “Same Port” type where the device only controls the negative side of the circuit.

Virtually all BMS only switch the negative side. Unless it uses a contactor, instead of FETs, that's pretty much all you're going to find.

With a contactor, you can use one with multiple poles and sets of contacts, and have it do whatever kind of switching job you prefer.

I was planning to only connect 14 of the possible 24 balance wires, it was adamant that this was an unwise configuration,

Some can be used this way, and some can't. You must check the manufacturer documentation (see above) to find out if it can be used this way, and how to wire it, if so.

Incorrectly wiring it you can blow up the BMS, or cause it to detect incorrect results, whihc could lead to cell damage or simply incorrect or no operation.

Some of them you leave all unused ones disconnected, and some you must tie certain ones together and then connect others in a specific order to your cells.

Is the idea that being a smart BMS, these parameters are configured in the app?

You'd have to check the app itself, or the documentation from the manufacturer, for your specific BMS.


Side note: JBD is popular, and therefore there are clones and counterfeits which may or may not operate the way the real ones do, or be wired the same way, even if they show the same model number. So anything purchased from somewhere other than the manufacturer directly should be carefully checked against manufacturer documentation to be sure it's real, and tested to be sure it operates as expected under all conditions it must protect against.

 

[A-DamW]

it was adamant that this was an unwise configuration

I have some JBD's, and have spent some time on their website.

Here is the wiring diagram for the model you have on their site:
DB24SA03
specifically this pic:

Looks like you can go as low as 10s.
I think you can run 14s on this model just fine.

 

[Bonwit]

You can get the documentation from the manufacturer website, which can be quickly found with a general websearch:
https://www.google.com/search?q=jbd+bms
or one specifically for your model (which shows the documentation in the second link for the results I get here)
https://www.google.com/search?q=JBD-DB24SA03

I'm surprised the AI didn't point you there, since you have the exact model of BMS, etc.




Virtually all BMS only switch the negative side. Unless it uses a contactor, instead of FETs, that's pretty much all you're going to find.

With a contactor, you can use one with multiple poles and sets of contacts, and have it do whatever kind of switching job you prefer.





Some can be used this way, and some can't. You must check the manufacturer documentation (see above) to find out if it can be used this way, and how to wire it, if so.

Incorrectly wiring it you can blow up the BMS, or cause it to detect incorrect results, whihc could lead to cell damage or simply incorrect or no operation.

Some of them you leave all unused ones disconnected, and some you must tie certain ones together and then connect others in a specific order to your cells.




You'd have to check the app itself, or the documentation from the manufacturer, for your specific BMS.


Side note: JBD is popular, and therefore there are clones and counterfeits which may or may not operate the way the real ones do, or be wired the same way, even if they show the same model number. So anything purchased from somewhere other than the manufacturer directly should be carefully checked against manufacturer documentation to be sure it's real, and tested to be sure it operates as expected under all conditions it must protect against.

Thanks Amberwolf. Of course I consulted Google before anything, but wasn't sure that JBD is "Jiabaida". "Deep Seek" came up short, but it's early times. Thank you for the link. I have emailed Jiabaida to enquirer about the possibility of identifying this BMS as authentic, and am awaiting a reply. Your comment about testing the unit raises the question how one might go about doing that?

 

[Bonwit]

I have some JBD's, and have spent some time on their website.

Here is the wiring diagram for the model you have on their site:
DB24SA03
specifically this pic:

Looks like you can go as low as 10s.
I think you can run 14s on this model just fine.

A-DamW,

Thanks for the diagram. The balance wiring makes sense to me. What seems a little confusing is the wiring of the board itself. The way I read it is that the master positive of the battery connects directly to the load, but the master negative connects to B-, goes through the BMS and exits C- to the load. Do I have that right? Where I'm somewhat confused is the small B+ solder pad. I thought this connected to battery positive as some sort of sense wire, but the diagram says to connect this to the negative pole of the battery. Seems odd to connect it this way, but it appears to be related to an optional heating film for the pack, and determines whether it is powered or not. It just seems strange to have to connect anything to this if the heating film is not used.

And then there's the charging. I want to make sure I'm clear. If using a separate charge plug, do I also connect it to C- for negative, and tie directly into the positive lead from the battery for the positive side?

Sorry if this seems elementary to all of you who have done this before. I just want to take a step back and make sure I'm understanding this all correctly. Much appreciated!