My application supports variable pack configurations: 4S4P, 4S6P and 4S8P. Each one obviously uses a different BMS profile, and other minor changes such as charge/discharge MOSFET and fuse selections.

Data sheets for Li-Ion cells vary widely in terms of the specification parameters supplied, but the critical parameters are always given.

However, specific to (some) Sony (now muRata) 18650 VTC-series specs, such as the VTC6 and VTC5a data sheets, they list a "Max Cell Configuration" parameter.

Please note that these are not listed as test configurations (all other specifications pertain to the single cell).

Please also note that other Sony cells of the same MnO2 chemistry and similar DCRs do not specify this at all. In fact, no other manufacturers of high continuous discharge current 18650 cells, with even higher ESR specify "Max cell configuration" at all.

For the VTC6 (DCR=30A, Zcell=18mOhm) the parameter is called "Max Cell Configuration", and is spec'd 5S2P.

For the VTC5a (DCR=35A, Zcell=18mOhm) the parameter is called "Cell Configuration", and it is spec'd TBD.

I have not found this specified for any other 18650 cell by any other manufacturer within 30% similar capacity & DCR.

I presume this spec surfaces due to the very high DCR of 30A for the VTC6 (35A for the VTC5a). However, I can find no case of battery packs being limited in terms of the parallel or series pack configurations -- not in terms of a cell's specifications -- just in terms of BMS, wasted heat, partitioning protection and management circuits, etc.

Even if I use a VTC5a, it does not seem to me that "TBD" is even a valid specification, given they could come back later and stipulate 3S1P or any other arbitrary max cell configuration -- if that is important, should they not all have this parameter specified?

My question is, am I going to fail BIS, IEC, CE, or any other certification because of this specification, limiting me to 2P only? If I point it out, I will fail. If I do not point it out, I am liable.

BTW, I did try to get information from both Sony and muRata on this topic, to no avail, despite our intention to mass produce this product.


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