Paralleling JBD (Jiabaida) BMS

Hi Everyone,

Another question on paralleling several packs (each with their own BMS).
There's been some threads on this topic (which I all read), and the general consensus seems to be that it is ok to parallel packs.
Doing so increases the maximum allowed current of the system, so e.g. 3 packs of 100A in parallel creates 1 pack which can do 300A (best to have some safety margin in this case, so say 250A or so max).

Now I saw this new 13-20S 200A Jiabaida BMS (relay based) which seems quite cool, but in the listing on alibaba, it says:
"Parallel use of battery packs is not supported (battery packs are directly connected in parallel, and there is a problem of large current discharge of high-voltage battery packs to low-voltage battery packs)"
Now this stroke me as odd, they probably mean that you can't connect packs together when they are at a different SoC, right?
Well, no. I asked Fidelia of Jiabaida, and she replied that connecting two packs with this BMS in parallel is not possible at all, because:
"High series number bms does not support parallel connection. The voltage of a high number of strings is very high, and the current increases after paralleling, and the chip and MOS tube will burn out. The currents of the two branches will merge together eventually"
And this goes not just for this BMS, but also for their mosfet based BMS's. She tells me that it is ok to connect low voltage packs in parallel (such as 3x 100A 4S bms, that will yield you a nice 300A 12V pack), but for high series it ain't possible due to the "MOS tube buring out".
Now I'm not a complete idiot on this topic, but the reasoning behind this is beyond me. I can't seem to understand why connecting several of these BMS's in parallel should cause any issue, especially when it's no issue for lower voltage packs. Also, I've contacted several other BMS manufacturers, and none of them confirm this issue, they all say it's no problem for their BMS.

Is there anybody who can clarify this?

Wal007 said:

Now I saw this new 13-20S 200A Jiabaida BMS (relay based)

Is there anybody who can clarify this?

Click to expand...

I can. I have two of those BMS right here. Sold quite a few over the last few months. If the ones I sell are teh ones you talk about?

I sell the model SKU: AP20S002-200A-Lithium ion type. THere is also the SKU: AP20S004-1. 200A relay based Jiabaida. 1/4 Amp balance current.

I like the one cause it hits the RV solar market voltage ranges (8s).

You can parallel them just fine ( the one I order). They dont care they have their individual shunts. Big heavy 600A shunts keeping cool at 200A.


I dont know about the 13-20s one. I dont know how it senses its current.

Is this it?

https://www.lithiumbatterypcb.com/product/13s-to-20s-li-ion-or-lifepo4-smart-bms-relay-solution/

I sell this one.. 200$ shipped. US.

https://www.lithiumbatterypcb.com/product/7s-to-20s-200a-smart-bluetooth-bms/

Thanks for your reply!

The specific model I'm looking into is the JBD-AP20S004, so yeah, the one you attached a link to

Good to hear you can parallel them just fine, but at 8S if I understand correctly.
What Jiabaida is telling me, is that for 4S and 8S it's fine, but for higher series (like 16S, my intended use) it ain't.
By the way, they say the same thing goes for all their other BMS, so not just this model.

But when you keep the packs together (connected), it's my understanding that the voltages will remain roughly equal, so no excessive currents will flow between the packs. So I don't really get why all of the sudden they are telling me it's not ok to parallel them.

Wal007 said:

Well, no. I asked Fidelia of Jiabaida, and she replied that connecting two packs with this BMS in parallel is not possible at all, because:
"High series number bms does not support parallel connection. The voltage of a high number of strings is very high, and the current increases after paralleling, and the chip and MOS tube will burn out. The currents of the two branches will merge together eventually"
And this goes not just for this BMS, but also for their mosfet based BMS's. She tells me that it is ok to connect low voltage packs in parallel (such as 3x 100A 4S bms, that will yield you a nice 300A 12V pack), but for high series it ain't possible due to the "MOS tube buring out".

Click to expand...

This is standard nonsense Chinglish. You're talking to an export rep with no technical knowledge/info and minimal English proficiency, certainly not in the same location and quite possibly not even with the actual manufacturing factory.

Yeah, that's what I was thinking. I'ts probably fine, I just found it weird that they are pushing this specific point so vigorously.
Thanks for the replies guys!