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Discrepancy in kWh display for charging

Discussion in 'Prime Main Forum (2017-2022)' started by GeekOne, Feb 17, 2023.

  1. GeekOne

    GeekOne New Member

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    I had a chance to charge at a charge station today that displays the electricity consumed. It showed I used 3.41 kWh over the course of an hour. When I look in the Toyota app, it shows the charging session used 2.331 kWh with only a few seconds different on the charge duration, taking the battery from 58% to 95%. The charger was a SemaConnect model 630. I am going to assume the Sema is correct since that is the consumption used to bill the customer. Is there any way to "calibrate" the onboard meter so it is more accurate? It appears my calculations on how much each charge costs me at home has been a quite a bit off. It's still less expensive than gas, by far, but I'd like to have accurate data so I know what I'm actually using.
     
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    I fixed your title to state “kWh” since you’re talking about energy.

    The EVSE shows you how much got dispensed. The car probably shows how much actually went into the battery so there’ll always be a difference in what was pulled from the wall and what actually goes into the car.

    That said, a 30% loss seems really high (usually you’d expect a 10% loss). Unless the battery heater was running to bring the battery temperature up to above freezing for better charging.
     
    GeekOne, hill and Trollbait like this.
  3. MalachyNG

    MalachyNG Active Member

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    I don't know where the app is pulling the data because it says every charge is exactly 4.41 whenever I plugged in with half a battery left or dipped into the hybrid reserve. The EV Connect I sometimes have access to at work varies from 6.0-6.3
     
  4. Salamander_King

    Salamander_King Senior Member

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    I never used the Toyota App, so I can't be sure, but I have a similar remote app, FordPass on my current Escape PHEV. It too reports a vastly smaller amount of kWh per charge compared to what was actually drawn from the wall. 20 to 30 % lower kWh is reported by the app.

    BTW, my estimation on PP was about 15% conversion loss from the wall to the traction battery.
     
    #4 Salamander_King, Feb 18, 2023
    Last edited: Feb 18, 2023
  5. hill

    hill High Fiber Member

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    I wonder if the Toyota feature presumes energy lost coming in - and going out as well. After all there is DC to AC conversion loss too.
     
  6. john1701a

    john1701a Prius Guru

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    Though for bZ4X, it's easy to see the same approach being applied to the upcoming new Prius Prime. With regard to the 2017-2022 models, I never bothered to check. Even BEV purists were blowing off kWh consumed as unimportant; all they seemed to care about was range. So, it was pointless arguing. Eventually, overall efficiency will come back to haunt those who didn't take it seriously. Anywho, the following information (from a press release for the Toyota market in Finland a few days ago) seems quite relevant to the topic of accounting for energy loss:

    The logic of the information displayed in the instrument panel is changed, e.g. in terms of energy consumption, to better match the consumption during the driving event. The displayed energy consumption is reduced by about 10%. Thus, it better corresponds to the industry's general practice, where the energy consumption shown in the car's instrument panel does not take charging losses (approx. 10%) into account.

    The updates will be available starting in May 2023, both for the production of new cars and as software updates performed at a Toyota dealer for cars already manufactured.
     
  7. Trollbait

    Trollbait It's a D&D thing

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    Wouldn't ignoring the charging loss on the car's display for the trip be like ignoring the portion of gasoline lost as heat out the exhaust?

    The EPA ratings are based on an amount of electricity consumed at the wall outlet.
     
  8. Salamander_King

    Salamander_King Senior Member

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    For me, the most important data is how much kWh of electricity is drawn from the wall. That is the only way to know the real cost.

    Yeah I would also like to know how much of that went to the battery and then how much of that was used to move the car. But, that's not for the cost analysis.
     
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  9. john1701a

    john1701a Prius Guru

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    Their statement saying... it better corresponds to the industry's general practice ...is what some were begging for. Toyota tries to follow the path of sensible & logic, doing their best to ignore rhetoric. This is far from the first time having to succumb to precedent others set. Ironically, it tends to blow up in the face of those who posted countless "kicking & screaming" complaints because they fail to consider the bigger picture... like actually measuring the electricity consumed.

    In an interesting twist though, that mi/kWh outcome can be misleading with a PHEV from the use of hold mode. Saving EV for when you are driving through town, using HV while on the highway, results in a higher value. What's shown is indeed genuine. You're avoiding high-draw conditions to make the most out of limited capacity... which is exactly what an owner should do. However, results would end up different from if you had just driven EV until depletion.

    At this stage, it doesn't really matter though. We're back to audience again. Who is using that kWh value and for what purpose?
     
    #9 john1701a, Feb 18, 2023
    Last edited: Feb 18, 2023
  10. hill

    hill High Fiber Member

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    Is anyone / someone really making 3rd grade division into rhetoric?... coming back to haunt 'those people' ?
    A home or commercial evse shows 10kwh out .... & there's (eg) 20 or 40 miles driven. Where's the mystery. That's either 2 or 4 miles/kWh turning on whether you went 20 or 40 miles. Is there some kind of history or drama when someone does simple division?