How does the Volt calculate MPGe or Le/100km?
Grab our Forum Feed

+ Reply to Thread
Results 1 to 5 of 5

Thread: How does the Volt calculate MPGe or Le/100km?

  1. #1
    Join Date
    Apr 2017
    Location
    Ontario, Canada
    Posts
    5

    Default How does the Volt calculate MPGe or Le/100km?

    The Volt's calculation of MPGe or Le/100km, which should be based on a fairly standard calculation, comes up with a value that does not make sense to me. For instance, it routinely gives me around 100MPGe (2.3Le/100km) for my daily commute, which is about 87km (54 miles) on a full charge (14.6kWh). By most calculations, this should land closer to 1.9Le/100km or 125MPGe.

    I'm wondering why there seems to be such a discrepancy. The industry accepted conversion is around 1-gallon to 33.70 kWh, so for my commute, 14.6kWh=0.43gal, 54 miles/0.43gal = 125MPGe.

    Any thoughts?

  2. #2
    Join Date
    Jun 2014
    Location
    Austin
    Posts
    418

    Default

    Quote Originally Posted by Lasidar View Post
    The Volt's calculation of MPGe or Le/100km, which should be based on a fairly standard calculation, comes up with a value that does not make sense to me. For instance, it routinely gives me around 100MPGe (2.3Le/100km) for my daily commute, which is about 87km (54 miles) on a full charge (14.6kWh). By most calculations, this should land closer to 1.9Le/100km or 125MPGe.

    I'm wondering why there seems to be such a discrepancy. The industry accepted conversion is around 1-gallon to 33.70 kWh, so for my commute, 14.6kWh=0.43gal, 54 miles/0.43gal = 125MPGe.

    Any thoughts?
    I'm not familiar with Le/100km, but MPGe is based on power from the plug, not power from the battery. There is a 12%-20% charging overhead. I'm averaging 15.8kwh to fully charge the battery which uses 14.0kwh (13% overhead), but I think GM's mpge calculation uses a value closer to 16.8 kwh to fully charge the battery (20% overhead). The actual charging overhead may also be a few percent higher (closer to 20%) with L1 charging than with L2 charging, and would also be higher in the heat of the summer with more kwh required for the battery thermal management system (TMS) for cooling during charging. I think the car's estimate uses the pessimistic 20% charging overhead value in the MPGe calculation, instead of the more realistic 13% value for charging overhead.

    So the calculation would use 33.7 kwh/gallon equivalent. Let's assume 20% overhead to fully charge the battery
    miles / gallon_equiv = miles * (1/kwh)*(1/charging overhead * (kwh/gal) = miles * (1/1.2) * 33.7 / kwh

    For the Op's case: 54 miles * (1/14.6kwh) * (1/1.2 overhead) * 33.7 kwh/gallon = 104 mpge
    If the Op is charging with L2, the "correct" mpge number might be (54 / 16.0kwh) * 33.7 kwh/gallon = 114 mpge
    Last edited by Sheldon; 3 Days Ago at 11:07 AM.
    Hidden Content 2017 Volt Premier Pepperdust metallic Jet Black/Brandy w/pkg I & II, AAC; Clipper Creek LCS-20

  3. #3
    Join Date
    Apr 2017
    Location
    Ontario, Canada
    Posts
    5

    Default

    That's definitely something I did not consider! Has anyone done real-world measurements of wall-to-wheel efficiency? I am running a 240V Schneider EV230WS if that matters.

  4. Remove Advertisements
    GM-Volt.com
    Advertisements

  5. Advertisement

  6. #4
    Join Date
    Sep 2016
    Location
    Chicago (W Suburbs)
    Posts
    467

    Default

    That could vary wildly with environmental and other factors. Depending on the ambient temperature of the charging site, the A/C or heater may have to run occasionally. If the cells become unusually unbalanced somehow, it may take more power to balance them. Even a difference of 220v versus 240v (actual line voltage) could make a difference. I'm not sure if it also counts any preconditioning draw from the outlet in the MGPe; I wouldn't be surprised if it did.
    2016 Kinetic Blue LT

    Unscheduled service visits: 4 Hidden Content
    Longest service visit: 2.5 weeks

  7. #5
    Join Date
    Feb 2014
    Location
    Portland, OR
    Posts
    573

    Default

    Seems to me the price you pay for each kWh of grid power stored in the battery depends on the efficiency of the refueling methodology (L1, L2, or plugless recharging). Your fuel mileage, i.e., how the Volt performs using the available fuel, shouldn’t be affected by how you filled your fuel tank.

    The distance you drive on each kWh of grid power doesn’t depend on how you charged that battery. Should your MPGe go down only because you started using a plugless recharging system?

+ Reply to Thread

Quick Reply Quick Reply

  • Decrease Size
    Increase Size
  • Remove Text Formatting
  • Insert LinkInsert ImageInsert Video
  • Wrap [QUOTE] tags around selected text

Similar Threads

  1. calculate how much it is costing me per charge?
    By acvolt in forum Generation 1 Volt (2011-2015)
    Replies: 13
    Last Post: 04-22-2015, 04:52 PM
  2. So any of you number crunchers want to calculate the 5 year cost of owning volt/bolt
    By Taser54 in forum Chevy Volt General Discussion, News, and Events
    Replies: 1
    Last Post: 01-12-2015, 12:36 PM
  3. How does one calculate amount of gas used?
    By soundmike in forum Generation 1 Volt (2011-2015)
    Replies: 18
    Last Post: 06-08-2014, 12:27 AM
  4. L/100km estimation accuracy
    By Matt-Volt in forum Li-Ion Battery, Charging, & Battery Managment System - Chevy Volt
    Replies: 3
    Last Post: 09-14-2013, 09:19 PM
  5. Volt console display for Australia l/100km
    By brewster in forum Newcomers to GM-VOLT.COM (See here for FAQs)
    Replies: 4
    Last Post: 04-15-2012, 09:49 AM

Bookmarks

Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts