fully charged indicated range is dropping?

Predicted EV range is no more of a battery capacity indicator than the DTE is of the gas tank capacity. Well, maybe a tiny bit more. Mostly it's an indication of how efficiently (or inefficiently) you've been driving. Go to your eco page and look at your miles/kWh history. That will tell you your efficiency and, unless you've been subjecting the car to extreme heat, will probably reveal the real reason for the reduced range.

To measure capacity, put a kWh meter on the outlet you charge from and see how that kWh per charge compare. Keep in mind that it will fluctuate bases on how far you have dipped into the HV portion of the battery.

 

But 'Charging Loses'.
What 'goes in' is not the kWh capacity of the pack.

Plus EV/PHEV's have a thermal management system that cools or heats the pack as required, (the good ones) and that power usage shows up on the kWh meter.

 

And your estimates are based on past practices; so if your using your A/C more - the computer is going to deduct the usage from your EV range. Since your going to getting less miles/Kwh.
Jerry is correct, you need to look at your historic m/Kwh usage tables.

 

MikeT12 is in the bay area, where we have been having temperatures as high as 100 degrees in recent weeks. I'm assuming that the "bay area" in his profile is the San Francisco bay area.

I've found that it will show a higher range if you turn off the AC before shutting down the car. This is because the predicted range is based on the previous driving technique as well as the current settings. If the AC was used when you came home, it will still be "on" when you start the car in the morning. As soon as you turn the AC off the predicted range should increase.

 

it's actually just the fan

 

That overhead is a lot more consistent than the driving efficiency, but, yes, it fluctuates as does the SOC when you initiate charging. Measuring from one charge to the next is about like trying to figure gas mileage on a Gen 2. But over time, you will see a clear trend if there is one to be seen. Here's mine for the last 2-1/2 years as an example:

 

As pointed out, the GOM (Guess-O-Meter) EV range displayed is not a good value to judge the battery capacity. You can make it to display far larger than what the actual EV range is or it is also so easy to drop the number lower in a short span of time by just driving with a very heavy foot. It is just a prediction based on the past EV efficiency.

And if you record the ACTUAL day-to-day EV range not the estimate on the GOM, it actually fluctuates even more widely than the GOM numbers. Below is a graph of the ACTUAL EV range recorded on my 2021 PP over the past year since it was first purchased. Daily variation of 10 miles or more either up or down is very common.

Any changes on the GOM number, I would not worry about it.

 

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This pic was taken yesterday. Today my range after charging was 40.2. It's a 2020 Prius Prime with 20k miles. I notice a falloff in the winter. I've seen it as low as 29 miles. In the summer the range seems to have slightly increased with more use. Temp and frequency of use seem to be the biggest factors. Lately, I've been doing a full charge daily, and running all the miles out daily - I rarely park it overnight with any charge remaining. Also, if your environmental systems are on after charging you'll lose a couple miles.

 

I am glad to see you had a couple of measurements around 5.4 KWh and then it went back up again. I got nervous when I only was able to add 5.53 KWh today charging from less than 1% charged to a full charge at my local charge point station. I then went back to my history and tried to find my longest charging sessions. It looks like there might be a trend, but your data puts my mind at ease a little. I don't know the exact charge level at the start of the earlier charging sessions, so my data can't be that accurate.

--------------- Estimated Useable Battery Capacity --- Notes
2/23/20 ----- 6.12 KWh -------------------------------------- unknown state of charge to full charge at chargepoint station
9/2/21 ------ 6.05 KWh -------------------------------------- unknown state of charge to full charge at chargepoint station
5/13/22 ---- 5.89 KWh -------------------------------------- unknown state of charge to full charge at chargepoint station
11/16/22 --- 5.73 KWh -------------------------------------- unknown state of charge to full charge at chargepoint station
1/5/2023 --- 5.53 KWh -------------------------------------- <1% to full charge at chargepoint station

 

You do have quite a trend going there. Keep in mind, too, that once you hit zero EV range, the battery can still go lower as you continue driving in EV mode. Without an OBD2 device and app to check the actual SOC, it's hard to get a clear idea from the little battery indicator of how deeply it's discharged. But for a series of them to each be more discharged than the previous time would be quite a coincidence. I still think it'll come back, though. Just have to wait and see.

 

Even if it is really trending down that significantly, I doubt it will go to zero before age and use kills the battery. I put ~ 55,000 miles on it since I purchased it in February 2020. Even if it loses ~10% every 3 years/55,000 miles, it will be 9 years old with 165,000 miles on it before the batery capacity reaches 70% of its original capacity. I think I may be losing capacity because I fully charge the vehicle overnight and partially charge it 2 times during the day to do all or most of a 70 mile round-trip commute in EV mode. I wonder if this is as much wear on the small battery as driving 700 miles a day 5 days a week on a 250-300 mile range BEV? I don't think Toyota's battery warranty has any limits on how much you can cycle the battery, so I figure I am still getting my money's worth, even if the warranty doesn't cover degradation.

 

Yeah, you might be a prime (no pun intended) candidate for battery degradation with two cycles a day.

 

When my 2017 Prius Prime was new I was getting 33-34 miles of EV range in the summer (30 or 31 in the winter), 7 years later and with an odometer reading of 32,000 miles (I'm retired) I now get a full charge of 24 (winter) and 26 or 27 in the summer. My Prime is garaged and kept on charge when parked. This deteriorated EV range still isn't too bad, but the handwriting is on the wall, some of the battery cells are obviously beginning to fail and sooner or later I'll need to replace the EV battery. I'm curious if anyone has asked their Toyota dealer what the cost of a new (or perhaps refurbished) EV battery replacement is for their Prius Prime?

 

i honestly don't think you will ever need one. i think they can be replaced i quadrants at $3 or 4,000. each plus labor, but i haven't asked.

 

The battery pack is still under warranty and the vehicle will still remain drive-able all the way down pass the HV only battery indicator. That being said, the question is do you want to part with the money to get the car back to 100% or do you just drive it around with the CEL on - kinda like the people who ignore their TPMS lamp? Different rules apply for CARB state cars, since it wouldn't pass annual or semiannual state inspections.

 

Update: My estimated capacity seems to have improved since it's low point in winter 2023. Now that I have more data, the trend is a little less clear. Looks like it is handling 2.25 cycles per day, 5 days a week pretty well as far as I can tell. Here is a graph and table of estimated useable capacity based on KWh charged at charge point stations.