Battery Module Numbering - Do We Really Have it Right?

I am racking my brain trying to figure out how going from left to right (Starting at the negative cable), going in pairs, with cells 1 & 2 being module #1, cells 3 &4 being module #2 and so on, really works. I've read countless posts on module numbering and have yet to find one that provides any type of rationale, reference or basis as to how they are qualified to reliably provide the information.

The reason for my confusion is based on the placement of the sensor wires in the pack. While there are indeed 14 sensor wires accounting for the 14 modules, those wires do not seem to correspond to the numbering system above and is what seems to be universally accepted. When we look at the sensor wires, no wire exists on cell 1 or 2 (presumably module 1). Sensor wires are located on cell numbers 3, 5, 7. 9, 11, 13, 15, 17, and 19, then they change to even numbered batteries on cell numbers 20, 22 and 24 (see attached photo). Based on the placement of sensors, module 1 would not have a sensor and module 10 would have 2.

I get that the negative and positive main cables can also be sensor wires in and of themselves, and that the safety cutoff correlates with the change from odd to even numbered cells, still it doesn't all add up for me and I'd still be guessing instead of knowing. It would make a lot more sense, given sensor locations, if the modules were based on cells 24 & 1 being a module, then 2 & 3 being a module, then 4 and 5 and so on.

Is there anyone here that actually knows (not got it from someone else who got it from someone else) if the numbering system that has been widely accepted as fact, is true or not. If it is true, could you also please explain, with definitive knowledge, how the sensors work in the commonly accepted module numbering system? It would be nice to see an answer that explains how it works, why the person giving the answer is qualified to provide the answer along with a reliable reference that supports the information.

The only way for me, as a person who is not an electrical engineer and has not been factory trained by Toyota, to determine the answer, would involve 9 complete removals, tear downs, re assemblies and installations of the traction battery. That being taking a bad cell and successively moving it through positions 1, 2, 3, 4, 19, 20, 21 and 24, generating codes and correlating those codes to module numbers. Add the reassembly to normal working condition and there is 9. Hopefully there is someone that can assist in avoiding that process.

PS. I may be a new member, but have very actively used Prius Chat for the past 8 years as a reader. I joined as I cannot find anything out there that discusses this beyond the question.

 

Not sure why I can easily edit tags but not my post. I did not identify all cells in the module making a few areas of my post make little sense. Here is the revised and corrected post. Sorry.

I am racking my brain trying to figure out how going from left to right (Starting at the negative cable), going in pairs, with cells 1 & 2 being module #1, cells 3 &4 being module #2 and so on, really works. I've read countless posts on module numbering and have yet to find one that provides any type of rationale, reference or basis as to how they are qualified to reliably provide the information.

The reason for my confusion is based on the placement of the sensor wires in the pack. While there are indeed 14 sensor wires accounting for the 14 modules, those wires do not seem to correspond to the numbering system above and is what seems to be universally accepted. When we look at the sensor wires, no wire exists on cell 1 or 2 (presumably module 1). Sensor wires are located on cell numbers 3, 5, 7. 9, 11, 13, 15, 17, and 19, then they change to even numbered batteries on cell numbers 20, 22 24, 26 and 28 (see attached photo). Based on the placement of sensors, module 1 would not have a sensor and module 10 would have 2.

I get that the negative and positive main cables can also be sensor wires in and of themselves, and that the safety cutoff correlates with the change from odd to even numbered cells, still it doesn't all add up for me and I'd still be guessing instead of knowing. It would make a lot more sense, given sensor locations, if the modules were based on cells 28 & 1 being a module, then 2 & 3 being a module, then 4 and 5 and so on.

Is there anyone here that actually knows (not got it from someone else who got it from someone else) if the numbering system that has been widely accepted as fact, is true or not. If it is true, could you also please explain, with definitive knowledge, how the sensors work in the commonly accepted module numbering system? It would be nice to see an answer that explains how it works, why the person giving the answer is qualified to provide the answer along with a reliable reference that supports the information.

The only way for me, as a person who is not an electrical engineer and has not been factory trained by Toyota, to determine the answer, would involve 9 complete removals, tear downs, re assemblies and installations of the traction battery. That being taking a bad cell and successively moving it through positions 1, 2, 3, 4, 19, 20, 21 and 28, generating codes and correlating those codes to module numbers. Add the reassembly to normal working condition and there is 9. Hopefully there is someone that can assist in avoiding that process.

PS. I may be a new member, but have very actively used Prius Chat for the past 8 years as a reader. I joined as I cannot find anything out there that discusses this beyond the question.

 

Thank you Truth Seeker and ChapmanF for the great explanations. This is exactly what I was looking for. While I can read an electrical schematic, I never was privy to one until now. I will have to take my pack apart soon as Dr Prius is showing high internal resistance in a few of the blocks and I am not getting maximum charge and discharge. I didn't want to enter the project second guessing the basics. Thanks again.