SoC over 100%

If you read what I wrote... then you should understand why I want to compare the usable SoC %...

 

And the watt-hour meter will provide this comparison.

 

You are not getting my point. I already have said that the sample numbers are too small to make the comparison statistically significant. That's why I want another line of evidence to support my hypothesis that 2021 PP has a slightly more SoC allowed for the EV Mode drive. I already have enough numbers of SoC data from 2017, all I want is to compare that data to the same SoC data I obtain from the 2021 PP.

 

The watt-hour meter will tell you how many watt-hours came out of the wall. That will be the sum of the watt-hours that went into the battery plus the watt-hours that went into the charger cooling fan, plus the watt-hours that went to the computers, plus the number of watt-hours consumed by any battery cooling that might have been needed, plus the watt-hours that went into making the wires warm, plus the tiny number of watt-hours used by the meter itself. All you really know about what went into the battery is that it's less than what came out of the wall. It's good for tracking trends, but not a precise measure of battery capacity.

 

Correct, but it gives a good comparison.

 

Another point is that the charge kWh comparison alone does not distinguish the two possible reasons for the increased EV range in 2021 vs 2017 I have mentioned.

If the kWh charge is slightly larger in 2021 than in 2017, it could be due to the threshold change or slight variation in the battery capacity. SoC% data will distinguish those two alternatives. If the SoC data comparison is the same, then the physical capacity difference is more likely. But if the SoC data shows 2021 has more usable SoC%, then software change to set the threshold is more likely the reason.

 

The HV battery hasn't been changed since 2017 according to Toyota Parts. What you are seeing must be due to other reasons, such as battery degradation or seasonal effects.

2017 Toyota Prius Prime—Stack subassembly, HV supply, No. 1—G950847230—Genuine Toyota Part

 

We all know the physical battery and specs have not changed. That is the assumption. But are all the batteries coming off factory assembly have 100.00% exactly the same capacity? Maybe there is a slight variation between individual battery packs? QC may allow a +/-1% difference. If that is the case, then you could see a maximum of 2% difference between two cars having the same traction battery part.

 

Of course, there could be even a larger difference because of quality control in any type of battery.

 

If an individual battery pack showing more than 2% of the capacity variation is possible, then that can be the reason for my 2021 PP showing a slightly longer EV range than the 2017 PP did. But again, usable SoC% comparison will either strengthen or weaken that variation hypothesis possibility.

 

Why don't you try subscribing to TIS for one day ($15?) and download all the OBD codes and anything else you like so that you can see if any of them displays the actual SOC, which would eliminate the uncertainty arising from the third-party apps.

If the values given in your app are correct, I would be worried to drive with low SOC (under 5%) because that starts reducing the cell cycle life, as your actual SOC dips below 20%. The vanilla Prius may have a better buffer for low SOC than the Prius Prime because Prius Prime's large battery and EV capability may be is forcing Toyota to go to lower % SOC in the HV mode.

 

It doesn't do any good for my purpose. I can't check the 2017 PP and compare it to my 2021 PP. I have never used TechStream.

 

There's a limit to what TIS will tell you. Usually the manual will tell you, by name or description, what pieces of data Techstream will show you. I'm sure SoC is one of them. But it won't tell you the actual PID or scaling you would need to retrieve it with anything that isn't Techstream. And Techstream itself will show you the value, again by name/description, but won't show you the PID info.

For most generations, there is PID info in circulation that you can program into some other scan tool to view the value, but people got that info by reverse-engineering it, not by reading it on TIS.

 

A direct measurement of the traction battery voltage when the display reads 100% should give a pretty good idea of the "real" SOC.

371.66V shown in the original post works out to 3.91V per cell, which is just about spot on for 75%.

 

Found this at Battery University:

Seems like this is precisely what Toyota is doing.