SoC over 100%

I do not know the answer to your question; but may I ask, what OBD2 reader you are using and what app on your phone? Android or Apple?

 

Yeah, it's normal in a sense that Dr. Prius always shows above 100% SoC when fully charged. This is a bug in the app, I believe. At the bottom of the SoC, when you used up the EV range, the app shows actual SoC which is 11-14%. You can use Hybrid Assistant App to check the real SoC. But for me, HA app has not been working on my new 2021 PP. It used to work on my other PPs.

 

The app's developer, @jacktheripper, is around here sometimes, maybe he has the story?

 

I see the same bogus SOC using Dr. Prius with an iPhone and any of the three OBDII adapters I own.

 

Yeah, if he can fix the bug, that will be great. I for one want to know the actual SoC in the traction battery, not the % displayed on the dash. For now, at least the app shows the correct lower threshold SoC when the traction battery is depleted of the EV range. And the in-between the full to empty on the dash, the corresponding SoC shown on the Dr. Prius app is perfectly linear. I think it is a very simple bug to fix.

Hybrid Assistant (HA) can read the real SoC as well, but for an unknown reason, I can not use HA App on my 2021 PP. I think it is the app update has a bug. The app installs fine but as soon as it recognizes the Bluetooth OBDII adaptor, it drops the connection. I tried using apps installed on three different Android phones and connecting to three different Bluetooth OBDII adaptors, but the same result in any combination I have tried. At least the Dr. Prius app is working and it shows lower-end SoC correctly.

 

Odd that it won't work on the 2021. I also have HA and really like it. But to use it, I have to drag out the ancient Android phone and charge it up. So it rarely gets used.

 

If you don't mind, will you try using it again? HA app has been updated. The current HA app version is Ver 3.3111.0. The android phone takes care of automatic updates. I have used the HA app on my 2017 PP and worked fine but did not use it on my 2020 PP for I did not drive the car that often. When I tried to use it on my new 2021 PP, the app was already updated, and now it can not stay connected to OBDII adaptors that use to work. Tried using my order Android phones but the same result. Since I don't have another Prius to try the app, I can't confirm that it is the updated HA app causing the problem.

 

I'll try to do that in the next couple days, @Salamander_King.

 

100% shown on dash is 100% actual. 0% shown on dash is 28% actual. So, 25%, 50%, and 75% shown on dash are 46%, 64%, and 82% actual, respectively, and so on.

 

Not according to the HA app. The buffer amount exists both on top and bottom. The top buffer is ~16%. Thus 100% SoC on the dash is actual ~84%. And bottom threshold when the EV range depletes is actual SoC ~14%. At least, that was the way in my 2017 PP. I would like to confirm this number has not changed on the 2021 PP.

If your observation that the total buffer amount is 28% is true for the 2021 PP, then the usable SoC for 2021 is ~2% more than what was available in the 2017 PP. If this is true, then it explains why the 2021 PP is getting a longer EV range than the 2017 PP. 2% SoC is not a lot, but it can be just enough to add a few miles for my round trip of 35-36miles commuting to be completed by 100% EV which was very difficult to do with my previous 2017 PP.

 

The reported battery capacity is 8.8 kWh. Since it takes about 6.3 kWh to charge the battery from 0% to 100% on dash, that should correspond to 72% of the actual capacity. This 28% actual SOC remaining when the EV allocation is consumed is also consistent with the magnified image of the dash indicator.

Overcharging leads to immediate cell damage, and I would think the transmission would disengage the motor–generator from charging the battery when 100% SOC on dash is reached, like when idling with a cold engine with 100% SOC on dash. Likewise, overdischarging reduces the cycle life, and that is prevented by the computer.

The HA app values can't be correct. They seem to be off by about a constant 16% shift, as you certainly have more than 14% in the HV mode when the EV battery is depleted.

Perhaps, the HV allocation isn't 28% as I estimated but 30% instead, but it's still right around 28–30%.

Thinking about it, a 30% HV allocation is probably more like it, as some of the 6.3 kWh you put is lost because charging isn't 100% efficient.

So, I will say:

100% EV SOC ≙ 100% total SOC
75% EV SOC ≙ 82½% total SOC
50% EV SOC ≙ 65% total SOC
25% EV SOC ≙ 47½% total SOC
0% EV SOC ≙ 30% total SOC

If you shift your HA app numbers by 16%, they agree with these numbers.

 

Is the 6.3kWh with L2 EVSE? Because I am using substantially more amount to kWh from 0% to 100% with OEM L1 EVSE. More like 6.6-6.8kWh. This full charge amount is also increased for the 2021 PP compared to my previous 2017 PP which was 6.5-6.7kWh, although at this point the sample number is too small to make the difference statistically significant. In any case, I still think there is a buffer on the top and bottom of the traction battery. For the reason you stated, the 100% SoC indicated on the dash can not be 8.8kWh of the charge in the battery.

That being said, how much buffer amount is left in the top and bottom are not important to me. The actual usable SoC for EV mode is what I would like to know using the same HA app. It was 70% for the 2017 PP. I believe it is slightly higher now for the 2021 PP.

 

Yes, ~ 6.3 kWh is what I used to get with the Level 2 ChargePoint stations. I haven't used Level 2 charging in a long time, as now, I charge at 120 V in my garage.

A 30% HV allocation for an 8.8 kWh battery is 2.6 kWh, which seems to be much higher than the battery capacity of the vanilla Prius HV. Perhaps, they keep the HV allocation larger on the Prius Prime PHEV (1) to make the car more efficient and (2) to extend the battery cycle life, as discharging below 10–20% actual SOC starts reducing the cycle life. A 30% HV allocation is my estimate, but perhaps, I am missing something.

The buffer above 100% SOC is a moot issue, as it should never be used since it would immediately damage the cells if it is used. A full discharge, while not damaging the cells, reduces the cycle life and may disable the car.

 

It is not a completely moot issue. You are correct that it is not usable, but if we believe the 8.8kWh spec of the battery to be the absolute full capacity of the traction battery, then whatever the buffer on the top reduces the total capacity of the battery by that amount. If you are correct in 30% of the 8.8kWh capacity is used for the HV mode, then that leaves 6.16kWh. If you can't charge the battery to the full capacity, then it leaves less than 6.16kWh of usable amount.

~14-15% for HV mode and ~15-16% for the top buffer is what I believe to be 70% SoC for the 2017 PP. 15% of 8.8kWh is 1.32kWh, which is about the size of a traction battery in a regular Prius isn't it? But, again, that top and bottom buffer amounts are not important to me for comparison of 2017 PP EV range vs 2021 PP EV range. What I want to find out is why the 2021 PP is getting a consistently longer EV range than the previous 2017 PP model. If no physical or mechanical change has taken place between those two model years, then the one plausible explanation would be the increase in the usable SoC on EV mode operation. That can be accomplished by a slight decrease in the buffer amount either at the top or at the bottom. Or alternatively, there may be some natural variation on the real full capacity of the traction battery such that my 2021 PP traction battery has slightly more capacity than the traction battery that came with the 2017 PP I use to own.

 

I owned a 2020 XLE as well, and I think the EV range miles and charging kWh were the same as for the 2021 Limited.

I think the better questions to ask are whether the Prius Prime battery can charge after 100% shown on dash, such as when idling with a cold engine immediately after a full charge, and what the lowest discharge level after 0% (--) first appears on dash is.

 

I have owned 2020 PP as well. For a small number of charges I have done, it was very similar to my current 2021 PP in terms of full charge taking more than 6.7kWh, unlike my previous 2017 PP which was around 6.5kWh. But I did not drive the 2020 PP often enough or long enough to have enough data points to make a good comparison. I don't know about being able to charge above 100%, for I have never tried it on any PP I have owned. SoC below --% depends largely on how long one drives after depleting the EV range, but that is not the question I am interested in. I am interested in comparing my data on the 2017 PP EV range to my current 2021 PP EV range. I can continue to record the amount of kWh needed to fully charge the battery, so soon I will have enough data points to make a definitive comparison between 2017 vs 2021. Usable SoC data is what I want but for now, without the HA app working, I can not make a direct comparison.

 

Well, if you have a watt-hour meter, you don't need to have the app because the watt-hour meter will tell you the usable EV capacity of your battery. Simply charge it right after the dash meter switches to "--" so that you know it is exactly 0%.