Electric Vehicle University - 102 Basic Concepts Part 2
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THE CENTRAL QUESTION ... I'm used to thinking about gallons and fill-ups, and now you're telling me I have to think in terms of amps and charging? What basic concepts do I need to understand before I delve into EVs in more detail? COURSE ABSTRACT A 2-part discussion of basic EV concepts, including volts and amps and measures of power and capacity that are necessary to understand battery charging. This mini-course also considers measures of vehicle efficiency including MPGe, kWh per mile and the e-Gallon. To obtain a copy of the EVU study guide for this and other available EVU courses, please complete the form on this page. Course level: Introductory
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Electric Vehicle University - 102 Basic Concepts Part 2
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- 2. 2 EVs—Basic Concepts, part 2 EV-102b This course is presented as part of Evannex University—a free, open learning environment that presents concise, video- based mini-courses for those who have interest in electric vehicles (EVs) …
- 5. Volts and amps in your garage Begin at your service panel Flow through wires to your EV Higher the voltage, the more amps can be delivered The more amps delivered, the faster your battery charges
- 6. Kilowatts (kW) and Kilowatt-Hours (kWh) A kilowatt (1000 watts) is a measure of power. But it’s also a measure of how quickly you fill your battery. A kilowatt-hour (kWh) is a measure of capacity—how big the bucket is.
- 7. Battery Capacity Small EVs—24kWh Large EVs—85kWh Larger results in Better range Better performance
- 8. Comparisons—MPGe Miles per gallon equivalent (MPGe)— indicates the number of miles an EV can travel using electricity that delivers the same energy content as a gallon of gasoline allows mpg comparisons e.g., the Tesla Model S EV gets 95 MPGe ?
- 9. Comparisons among Vehicles 9 E l e c t r i c V e h i c P l u g - i n H y b r i d H y b r i d s I C E V e h i c l e s Source: www.fueleconomy.gov
- 10. Comparisons among Vehicles 10 Electric Vehicles Plug-in Hybrids Hybrids ICE Vehicles Best 124 117 50 42 Average 95 92 42 28 Worst 63 88 28 12 Source: www.fueleconomy.gov
- 11. kWh per Mile Kilowatt hours per mile (kWh/mile)—is a measure of energy consumption, but also, A measure of the efficiency of an EV Typically, EVs consume between 0.35 to 0.50 kWh/mile The higher the speed the greater kWh consumption Source: http://blog.maxdunn.com/articles/2009/0 3/19/tesla-efficiency
- 12. e-Gallon (DoE) The price of an e-Gallon tells consumers how much it costs to drive an EV the same distance you could go on a gallon of gas … E-gallon ($/gal) = FE x EC x EP Where FE = average fuel economy of a comparable ICE vehicle EC = average kWh/mile of the top five EVs EP = average price of a kWh of electricity An online calculator can be found at: http://energy.gov/articles/egallon-and-electric-vehicle-sales- big-picture
- 13. Summary Volts and amps live in your garage kWh is a measure of the capacity of an EV battery MPGe, kWh per mile, and e-Gallon are all metrics that can be used to measure energy consumption
- 14. 14 … a free study guide for all EVU mini-courses is available for download from our website … For a complete list of mini- courses and the study guide, visit: www.evannex.com
Editor's Notes
- This presentation is a part 2 of our EVU mini-course discussion of basic concepts. If you haven’t already done so, please take a look at Part 1 before you proceed with this mini-course. We left off with a preliminary discussion volts and amps and their real world relationship to your EV. There are lots of additional things we could discuss, but the bottom line is how volt and amps play a role in charging your vehicle. And the best place to start is in your garage.
- For the purposes of our discussion here , volts and amps live in your garage. >> An electrician runs a line from your service panel—that’s the grey box on the wall in your basement or garage where your circuit breakers are located. He then runs a circuit—electrical wiring—to the location where the charging outlet for your EV will be located, usually in your garage. >> Electricity can then flow to that location. We’ll talk a lot more about why volts and amps matter as you set up your garage charging circuit in more advanced EVU mini-courses, so we won’t go into details here. >> Suffice it to say that the higher the voltage, the more amps can be delivered to charge your battery. >> And that’s important, because the more amps delivered, the faster your battery charges.
- Whenever EVs are discussed, you’ll likely hear people taking about kilowatts and kilowatt hours. >> A kilowatt (1000 watts) is a measure of power. But it’s also a measure of how quickly you fill your battery. >> A kilowatt-hour (kWh) is a measure of capacity—how big the bucket is or discarding the metaphor, how big your battery is.
- So when you see an EV manufacturer that >> touts a 24kWh battery, and >> another that talks about an 85kWh battery understand that the former has much less capacity than the latter, >> And as a consequence, >> the range of the first EV will be considerably less than the range of the second. >> In addition, the larger battery also leads to better overall performance—acceleration and top speed.
- But the bottom line is understanding how much you’ll save by driving an EV. Right now in the united states, gas prices are relatively low, but even today, filling an EV costs about 20 percent of what it costs to fill a conventional car. And if gas prices rise to, say, $4.00 a gallon—where they were for much of 2013, an EV looks even better in real dollar terms. With that in mind, two measures of consumption need to be considered—the first is: miles per gallon-equivalent >> Miles per gallon equivalent (MPGe)—indicates the number of miles an EV can travel using electricity that delivers the same energy content as a gallon of gasoline >> that allows mpg comparisons with ICE vehicles >> for example, the Tesla Model S EV gets 95 MPGe, 3 to 4 times better than comparable ICE vehicles
- It a bit difficult to do …
- It a bit difficult to do direct comparisons between the four different vehicle architectures on the road today, but we’ve made an attempt, and provided a chart based on US DoE statistics at the website fuelconomy.gov The “best” fuel economy in any vehicle category is always found in smaller, lighter vehicles, and the “worst” is typically associated with large heavier vehicles, like SUVs. The MPGe values attributed to hybrid and plug-in hybrid vehicles depend dramatically on the typical distance that such vehicles travel on a regular basis. If plug-in hybrids travel short distances only, they are comparable to EVs. However, if they travel longer distances regularly, say a 100 mile daily commute, their MPGe moves much closed to that of a fuel efficient ICE vehicle. The very best EVs can get about 124 MPGe, and the very best ICE vehicles get around 42 mpg. That’s a 3 to 1 ratio in favor of EVs!
- For EVs, there is another measure of consumption —kWh per mile. >> Kilowatt hours per mile (kWh/mile)—is a measure of energy consumption, but also, >> A measure of the efficiency of an EV >> Typically, EVs consume between 0.30 to 0.50 kWh/mile >> The higher the speed the greater kWh consumption The graph on the right side of your screen illustrates this for the Tesla Model S. The vertical axis is kWh per mile consumed and the horizontal axis is mph. It should come as no surprise that the faster your drive, the more energy you consume. We’ll look at the reasons why in another EVU mini-course.
- Another consumption metric is the “e-Gallon” developed by the US DoE. They define it in the following manner: >> “The price of an eGallon tells consumers how much it costs to drive an EV the same distance you could go on a gallon of unleaded gasoline in a similar car. ” If you’re interested in the technical details, here’s a quick summary of the e-Gallon calculation. >> E-gallon ($/gal) = FE x EC x EP >>Where >> FE = average fuel economy of a comparable ICE vehicle >> EC = average kWh/mile of the top five EVs >> EP = average price of a kWh of electricity >> An online calculator can be found at the link shown on your screen.
- In this continuation of our Basic Concepts mini-course, we expanded on some basic terms that are encountered repeatedly in discussions of EVs. >> Volts and amps live in your garage and have a significant impact of the way you can charge your EV >> kWh is a measure of the capacity of an EV battery >> MPGe, kWh per mile, and e-Gallon are all metrics that can be used to measure energy consumption and the relative efficiency of EVs In the next EVU mini-course in this sequence, we move on to EV architectures. That will help you to understand how EVs actually work, and what options are available for those who want to enter the EV world.