Identifying modules-blocks number on Gen 3

There's some information missing from your post: it seems you are looking at some report from Dr. Prius that has you concerned about block 5. Can you share what you are seeing there?

In the photo you have shared, the end of the battery marked "-Neg" is not the end I would call the Driver side. But your profile also doesn't show your location, so it might be the Driver side in your region.

 

If there's a P0A80 code, then it's not just Dr. Prius's opinion that the battery is pooped out; the car's own firmware has made that call.

There have been a lot of cars made with the same firmware, and with the same service plug connected to the same block, but I don't think I've seen any previous suggestion that the firmware might give false P0A80 judgments because there is a service plug.

I've done a quick google image search for dr prius internal resistance to see if I could spot any detectable pattern of Dr. Prius showing a higher IR reading for block 5 than for other blocks. I'll say that no such pattern has jumped out at me, and most screenshots I saw showed an IR for block 5 right in line with the others.

This could have a couple explanations: one, the IR figures are rounded to a milliohm (some screenshots have the milliohms displayed with one decimal place, but I have never seen one end with anything besides .0), and the added resistance of the service plug cable, plug, and fuse may come to less than that. (I have a microohmmeter and am not afraid to use it, but have never thought to go use it to measure that.) The other explanation could be that the car's firmware knows the expected extra resistance of those components, and subtracts.

Edit: the fuse in the service plug is, AFAIK, a 125 amp HV fuse made by PEC, and this PEC page is probably not the same exact fuse but a similar one, showing a resistance of 0.7 mΩ for the 125 amp flavor. Add a bit more for the extra wire and plug contacts, and I wouldn't be surprised to have an extra milliohm or so, all told. Which makes me think, since you don't see everybody's Prius tending to report block 5 IR 1 mΩ higher than the rest, that the firmware probably subtracts that.

 

It's possible you will run into the complication that what causes P0A80 is officially "TMC's intellectual property" according to the repair manual. The ECU is making dynamic judgments during car operation that are sometimes hard to second-guess with tests you can do yourself.

Sometimes you get more information by looking at the block voltages shown in the freeze-frame stored when the P0A80 was set, but there is a recent post where I have to say I have not spotted any particular block smoking gun even there.

If the car has judged a specific block to be at fault, it will generally set a P3011 to P3024 code identifying that block, along with the overall P0A80. If it has not done so, it might turn out that the P0A80 was set for some more general "TMC's intellectual property" reason that your testing might not pin down.