I will be the first to admit I can get obsessive when trying to understand things. I want to measure everything, record everything, analyze and then analyze my measurements and analysis for errors and tolerance. As many have suggested, the bottom line is cost per mile. When my new 2023 Prius Prime reports 33.9 miles driven at 3.8 miles per kWh, I start the analyzin'. 33.9 miles at 3.8 miles per kWh (with the AC on 75F with outside temp at 93F), took the SOC (State Of Charge) display from 100% down to 15%. My first analysis was to see if these numbers sound reasonable. I have seen folks using 11 kWh as the available power for EV mode going from 100% to ----% (zero). So 85% of 11 kWh would be on the order of 9 kWh. 33.9 miles / 3.8 miles per kWh = 8.9 kWh - looks reasonable. Next is to predict what using every available electron of battery power would allow under similar conditions: 33.9 miles / 0.85 = 39.9, so roughly 40 miles (and that is with the AC going full bore). Looks promising if it pans out. Next to find out how much those 33.9 miles cost me. I hooked up the charger to my US$12 Chinese meter and started my stopwatch. I also managed to get Dr Prius to successfully connect and found it reported the hybrid battery SOC at 32%. That also sounds reasonable, as even when the SOC showed ----% the color battery arc shows there is juice in the battery. This would suggest that reserve for HV mode to be around 17%. Out of curiosity, checking the Toyota app showed battery at 47%. This does not sound reasonable and we'll try to understand more about this later. 8 hours and 15 minutes later, the Toyota app popped a notification on my phone that the charging was complete. I raced to the garage, with my keys, to disconnect the charger from the wall. ( I had determined leaving the charging cable / charger connected to the car and wall after charge completion will continue to draw power, and the watt-meter timer will continue to run as will the kWh accumulation advance slightly. The meter showed 8 hours and 25 minutes but only 8 hours and 15 minutes had actually elapsed. (Confirmed by knowing the time I started charging, also confirmed by comparing the app "Charging Started" and "Charging Complete" notification times, and the stopwatch I started at the beginning.) Must not use the available 60 Hz events and is running fast. How fast? 2% and that just happens to correspond to one of the wattmeter's stated accuracies - 1% for voltage, 2% for current. They didn't spec the timer but now we know, 2% high. It might be possible the voltage is 1% low or high, the current 2% low or high, but the time is clearly 2% high. (I did a check with a 60W incandescent bulb - the meter showed 59W but I cannot know if the 59W is the real draw and the bulb is within some tolerance, or the meter power measurement is 1.7% low. If the meter power is 2% low and the meter timer is 2% high, it is possible the meter's kWh measurement is dead on. Considering the average daily charge is about $1 the 2% is probably 2 cents per day or 1/10th of a cent per mile. I should just ignore it but with time being 2% high, I'm going with the kWh 2% high.) The meter showed 11.78 kWh drawn from the wall. Since I know the meter has used a 2% high time value in computing the 11.78 kWh, I choose to derate the wall power by 2% to 11.54 kWh. The 120v AC had to be converted to higher voltage DC, and the cable resistance turned some of the current into heat, and the car was actively cooling the batteries in my 90degF garage, so it is reasonable to observe more power drawn from the wall to replace the 9 kWh used by driving. 11.54 wall / 8.9 battery = 1.3x wall to battery factor. I have never seen the "cost" of this loss discussed. Just like using the MPG the car displays versus using the miles driven divided by the actual gallons, the miles per kWh can be the car value of miles per battery kWh or miles per wall kWh. In my case, miles per wall kWh is going to be 1/1.3 less or 23% less. Car: 33.9 miles at 3.8 mi/kWh Per adjusted wall power: 33.9 miles at 2.9 mi/kWh Additionally, the cost per mile which is based on the cost of the wall power is increased: 11.54 kWh * $0.14294 = $1.65 and $0.049 per mile (real 2.9mi/kWh) Comparing that to my three previous HV only mode fillups at $0.067 per mile (real 46 MPG) Since the app would not have access to my power conversion factor, it could only report battery power of the charge. The app is totally crazy saying only 5.459 kWh was put into the battery to take it from the crazy 47% to 100%. Also interesting is that Dr Prius says the fully charged SOC is 116.5%.
There's definitely weirdness going on with the app; I drove the battery down to "Zero miles/ zero %" in EV mode; however, the app shows "30% charge" but no miles of EV range. I am now charging, I am at 32% but it is telling me it will take over 9 hours to charge. I also notice it has adjusted the gas range from 555 miles (first fill-up) to 468mi (I assume based on my average over the first tank?). after the second fillup. Also, based on the KwH and charging percentages listed in the charging log, the capacity of the battery (100%) is anything from 6 to 11 KwH (though it does cluster right around 10). So I am not really trusting any of these figures. I agree with you that the reserve for hybrid driving seems like ~17-20% charge. But even if the car charges itself above that, you don't gain any driveable EV miles (though if you are IN EV mode and recover energy through braking, you will see the EV range go up.) My EV range has been 37-41 miles per charge so far.
All the apps are at least slightly different. The best way I've found to be comfortable with whatever readings an app or the cars gauges show is to compare what you see and concentrate on the readings that match or are at least fairly close to each other. The readings that are not so close or grossly different can also be thought of as the app being configured using different baselines and needing conversions to make sense. It's always nice when posting to share where the readings being talked about are coming from and which model and trim is being described. thanks for sharing @nagrath
Or thought of as major failure to coordinate the software maintenance team with the model development team at any time during the final year the model is being readied for sale! The charge kWh value is totally bogus, not in any way “convertible to make sense. I’ve tried linear regression, polynomial fit, cluster fit, and a even a back-prop neural net model and the best I can tell, it is using a wrong but more precise than displayed starting charge percent to compute a wrong delta charge percent times a wrong available battery capacity around 10 kWh. Admittedly I may be the only customer interested in the value, as even an accurate value is primarily useful as input to personalized equations. The only correct app history information about a charge is the charge time (delayed availability after charge complete). The car and app do a terrible estimate of “time to charge”. A better estimate of charging time with the provided Lvl 1 charger from a 120v 15A circuit, and the car changed to max charge (from default 8A): miles driven / displayed average miles per kWh * 0.91 = hours (Seems to charge battery at 1.1 kW until final 30 minutes at 0.6 kW) and the estimated wall power will be: miles driven / displayed average miles per kWh * 1.35 = kWh (Wall rate is 120v * 12A = 1440 kW until final 30 min) I’ve only done one short level 2 (free power!) charge so not enough data for modeling yet.
Great info, this is very helpful (and nice to know I was not the only one finding those numbers really sketchy). Where is that Avg Miles per KWH displayed? In the app or on the MFD (So many screens, I am never sure if I have seen all of them)
I drive with the current and average miles/kWh "Eco" window open next to the speedometer. Expose the multi-information display Use the up/down, or left then up/down controls to select the "(leaf) Driving Info Display" Then us the right/left control to display the Power Consumption Display: In my 2009 Prius the indicated MPG (48.2) was 1.8 MPG high (46.4 actual). The energy in a battery, energy consumption, and recharge energy is much less knowable than physical gallons into a physical tank. Therefore I do not expect the indicated average power consumption (mi/kWh) to be as accurate as the indicated MPG, but it is a useful for estimating and modeling.
Ha! I have been driving in Hybrid mode to break in the ICE a little - and had only discovered that screen (showing avg MPG) after I ran out of EV battery - I charged overnight and boom, when I started up it was right there in front of my face. But thanks!
Taking a full set of pics of the gauges, at least once a year, is a good way to learn where they are and how to locate the ones you want to look at faster than scrolling through them all every time. I turn off the battery heater and turn on the battery cooler in late spring just so it will be easier to find them, since the cooler especially is buried deep in the MID's settings screens. Then I do the reverse in late fall. @tovli I hear ya, the app sucks, what else is new? I don't know why so many people load it up on their phones in the first place, hoping it will provide them more convenience or that one feature that they seem to think they need from it that only works if all the planets align and the moon is in the seventh house. Yous all might wanna check out Hybrid Assistant and see if that app works better with the Gen5. Hybrid Assistant: App and it's sister app Tire Assistant Tire Assistant I run them both on Android Oreo ie: 8
I'm new here with a 2024 Prius Prime XSE Premium. I'm glad I stumbled on this thread. I agree that the Toyota app for Android doesn't give reasonable data. It tells me that from nominal 0% to 100% charge takes 7.1 kwh. That would only leave 52% of the traction battery available for only EV mode. I've been using a level 2 charger. That app tells me it charges at 3.7 kw. 0-100% full takes about 11.6 kwh on that app. I hadn't thought about AC/DC conversion and line losses. That's very important to the overall per mile cost. I'm trying to determine my losses. I'm getting an average displayed mileage of 4.4 mi/kwh. I haven't driven the car enough to calculate actual EV mileage yet. I've read that the battery charging current is 16A. I'm not sure how that is governed. At 220V that would be a 3.5 kw charging rate, which I also believe is the maximum. So, if my battery really is being charged at 3.5 kw, and my level 2 charger app is saying 3.7 kw, it sounds like my charging setup is 95% efficient. I'm not cooling or heating the battery. My garage has been averaging about 50 F. I'm not sure what gauge the level 2 charger cord is, but it's rating for 40A, and my circuit is 50A, so at 16A I doubt I'm getting much line loss. That would give me a usable battery capacity of about 11 kwh (95% of 11.6 kwh) of the battery's 13.6 kwh total capacity. That seems reasonable. That would imply that about 81% of my battery is available for EV only range. Now for getting a full charge and driving straight through under mixed conditions until 0% nominal and the ICE kicks in. Then I can get my true mi/kwh value.
The official EPA value for the useable battery capacity at the 240-V plug is about 11.6 kWh (~ 11.7 kWh for SE, ~ 11.5 kWh for XSE/XSE Premium). So, the app, which shows the kWh at the 240-V plug, is correctly written. Note that the app does not measure the actual kWh, but it estimates it from the SOC by scaling the SOC, assuming 11.6 kWh at 100% SOC. Real Prime Battery Capacities | PriusChat As far as the energy loss on the battery charger, 5% is about right. My original post neglected the charger loss; so, the upper and lower buffers should add up to about 1.6 kWh.
5% is a ton better than 110V EVSE 25%+ loss (Kill-A-Watt telling me 13.4kWh to fill the 10.7kWh battery). I have a 2022 Leaf L2 EVSE from craigslist that I'm marking as 10% loss for my $ calculations, but with 2c/mile in EV benefits upgrading to a smarter EVSE is not in the future
I believe you are using an incorrect denominator for your calculations (should be the energy from the outlet 13.4). So if I'm correct the loss is 20%.
You are right, I didn't pay attention to what the convention is and just looked for the worst case number.
But you must consider what elese is being done as the traction battery is charged. The Traction Battery may be heated or cooled (Using AC chargee power or traction battery power), the 12v Battery may be recieving a small charge, and what ever elese is reqired for a prerequisite or cincurrent charger activity with the traction battery charging routine.
True, I tested over about 3 months, cold car, right after a trip, etc., it pretty consistently came out to 13.4-5. Maybe in the crazy hot summer it'll be different, I might try again soon.
