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Model 3 Charging Efficiency

Discussion in 'Model 3: Battery & Charging' started by insaneoctane, Apr 10, 2018.

  1. insaneoctane

    insaneoctane Active Member

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    Anyone done any testing to measure the M3's internal charging efficiency? Here's a MS thread that shows pretty interesting data, but I'd like to know the most efficient setting for the M3....
     
  2. PoitNarf

    PoitNarf My dog's breath smells like dog food

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    Stupid question, how does one measure this?
     
  3. Stretch2727

    Stretch2727 Engineer and Car Nut

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    You need to measure the total energy supplied versus the amount that gets to the battery.

    Generally the internal car charger loss does not increase as fast as the amount of power going in so the higher the power the more efficient the charging.

    Some examples based on numbers I have seen:

    110v @12 Amps = 1.3Kw - from your outlet.
    Subtract the 400 watts loss and only 900 watts is going to the battery.
    About 70% efficient. 900/1300=70%

    240V @ 40 Amps = 9.6Kw - from your outlet.
    Likely about 900 watts loss for 7-8x the energy
    About 90% efficient. 8700/9600 = 90%

    One reason to get a 240 volt setup. You will use less electricity.

    Bottom line:

    The higher the power the more efficient the charging.
     
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  4. Bad Horse

    Bad Horse Member

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    Yup, same principle of why AC took over the electric grid, lower current for higher voltage and thus same power (or at lest in the case of charger you get more power obviously but I digress). Essentially, current is not a "good" thing when it comes to trying to be efficient
     
  5. SageBrush

    SageBrush 2020: Drain the Sewer

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    This is a lot easier and cheaper today than just a few years ago. A $15 inductance sensor can track kWh to the EVSE and the car tells you how many kWh are added to the battery.
     
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  6. Veritas1980

    Veritas1980 Electric Viking

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    The API are supplying this data to my understanding, so I get the charge efficiency data on my teslafi.com page for my S.

    charge.JPG

    You can get the two first week for free or you are welcome to use my referral code for a free month, which is Veritas (case sensitive).
     

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  7. insaneoctane

    insaneoctane Active Member

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    This report is half the equation (like @SageBrush says), the other half is HPWC in vs out. Each of the two systems may have their own sweet spot and trying to find the best combination is what im interested in. I would discount instalation specific loses (like long runs that produce extra resistance)
     
  8. Veritas1980

    Veritas1980 Electric Viking

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    Ah, my mistake. I get what you are trying to acheive now.

    No, there a logging website can't help you out I guess. But an interesting project though.
     
  9. miimura

    miimura Well-Known Member

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    If I understand the data posted by @Veritas1980, it is really what you want, but for different current settings. That is showing the efficiency of everything inside the car because it is showing kWh AC vs. kWh into the battery. In a Tesla, the cooling pumps and fans consume a non-trivial percentage of power when the charging current and/or voltage are low (120V household outlet for example). The EVSE is going to take a fixed amount of power to operate, mostly the coil keeping the contactor closed, so that is going to give the smallest percentage loss at the highest current. Everything else is is resistive losses in the cables, which you seem to be willing to set aside.
     
  10. xav-

    xav- Active Member

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    Isn’t that the higher the voltage the more efficient the rating instead?

    Because whether I use 12 amp or 24 amp with 240 volts the miles per hour appears to be linear. When I switch to 110 volts though ir is no longer linear.

    30 percent loss on a standard outlet though really? Damn
     
  11. xav-

    xav- Active Member

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    I will post update tomorrow.. my electrician came this morning to replace the breaker but what it appears so far on 240V outlet:
    - 24 amp: 22 or 23 miles per hour
    - 12 amp: 11 miles per hour

    115 volts 12 amp: 4 miles per hour (so bad)
     
  12. SageBrush

    SageBrush 2020: Drain the Sewer

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    For the same amperage because the fixed losses will be lower (less time)

    Once you increase the amperage it usually overshadows the fixed loss savings.
     
  13. jsmay311

    jsmay311 Member

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    Edmund's is doing a long-term test drive of the Model 3. So far they've published 2 monthly reports/updates. In the first of those monthly reports, they listed both the measured average wall-to-wheels efficiency AND the displayed average battery-to-wheels efficiency (as displayed on the touchscreen).

    Here are the results:

    Current odometer: 1,388 miles
    Average lifetime consumption: 302 Wh/mi
    Average onboard consumption meter: 251.7 Wh/mi​

    Monthly Update for January 2018 - 2017 Tesla Model 3 Long-Term Road Test

    So they observed a 83.3% charging efficiency. (Or, if you prefer, a 20% charging overhead.)

    Hopefully they'll post the displayed efficiencies in more future reports, but since they chose not to in the 2nd report, I'm not optimistic.
     
  14. insaneoctane

    insaneoctane Active Member

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    This is more or less what I am after, only I'd like to see which settings maximum the charging efficiency because I can pick from multiple charge rates in the Tesla GUI....
     
  15. 03DSG

    03DSG Active Member

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  16. bartlettpsj

    bartlettpsj Member

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    I have had a model 3 for 8 months and have done about 8k miles. I have recorded every charge and reading available to me.

    Including what is in my battery at the moment I have done 7986 miles and 2161 kWh have been added (based on what the charging station reports has been used --- mostly Chargepoint or Supercharger). Each time I charge I record how many miles the car reckons it has added, and this has been 8876 miles in total. This means I have lost around 8% (92% efficiency). Not sure if this is just Phantom drain or charge efficiency or something else. Anyways, it has cost me $88 in total cos I have got mostly free charging from work and various places.

    Total cost is 1c per mile. Not bad. Saved me about $1200 in 8 months.

    Not sure if this is useful information to anyone.
     
  17. DrSmile

    DrSmile Member

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    I have been charging only on my 110 volt outlet (waiting for solar panels to be installed and the 240 volt outlet). I calculated that I am charging at exactly 4.6 miles/hour based on total miles charged overnight, assuming 75KWh pack for 310 miles that's 1,112 watts per hour from a 110 volt outlet at 12 Amps. This yields an efficiency of 84.2%, far better than the 70% I have seen posted. Am I calculating this wrong somehow?
     
  18. Dbregmam

    Dbregmam Member

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    #18 Dbregmam, Feb 7, 2019
    Last edited: Feb 7, 2019
    Bringing this thread back.

    I have a JuiceNet pro 40amp EVSE. I got my M3 AWD Dec 29th (just in time for the full tax credit). I was curious as to my usage as reported by the car compared to my charging as reported by the JuiceNet. I am disappointed by the result.
    I reset a trip meter when I got the car so I would have lifetime stats. The car is showing 345KWh used so far. I took a look at the JuiceNet logs and they show I have sent 425.19KWh to the Model 3. I have only done one smallish SuperCharger session so far, so the actual is even a little worse. This represents a 81% charge efficiency (not including the loss sent to the JuiceNet that is lost before being sent to the car). Is this low efficiency the car's issue or the JuiceNet? All of the research I have seen points to a much higher Level 2 charging efficiency - IEEE states that the mean L2 charging efficiency is 89.4%. I am in Southern California and charge in the garage, so temperature is not a factor.
    The only other factor that might contribute is that the the median charge amount is 7.52KWh - IEEE again states that "In those charges in which the battery took up less than 4 kWh, this difference in efficiency was even greater: 87.2% for Level 2..." So I would think this would increase, not decrease the overall efficiency.
    I took a look at the Edmund's article @jsmay311 refereed to, with a little higher efficiency then I am getting, the the graphics did not load, so I can not see the relevant data.
    Bottom line - all the research materials point to a MUCH higher charge efficiency then I see or Edmund's apparently saw.
    Any ideas?

    IEEE abstract for reference (if you are interested) - A comparison of electric vehicle Level 1 and Level 2 charging efficiency - IEEE Conference Publication


    ____
    Adding this thought - I seem to recall somewhere reading that the usage the car reports is for driving only, not 'idling'. As I do a fair amount of sitting in the car waiting for the kids at practice, I wonder if this has an impact. And if you are wondering, I do occasionally (when the car actually wakes up) pre-condition when the car is plugged in. But this is for 5 minutes max, so I can't image that is skewing things much.
     
  19. Dave EV

    Dave EV Active Member

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    If you're in the car and in park, the car is counting the amount of energy used. You can see this by resetting a trip meter and blasting the HVAC for a bit before driving off.

    But it does not account for energy used when the car is sitting "off" and locked. This uses up about 1% of your battery a day and accounts for your reduction in apparent charging efficiency.

    Tesla is the worst EV manufacturer that I'm aware of here. All other EVs that I'm aware of use a negligible amount of energy when off and you can let the car sit for months without seeing more than a few % of the charge lost.
     
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  20. insaneoctane

    insaneoctane Active Member

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    @Dave EV is exactly right. You can not compare the actual EVSE usage to the in car display. For only reasons Tesla knows, they decided to only show driving efficiency on the trip computer which leaves a lot of consumed energy unaccounted for. Driving efficiency is certainly a useful Stat, but with out stats it's misleading to say the least.
     

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