Re: [EVDL] EV Digest, Vol 95, Issue 30
> And I would like to see another term thrown in, since charging is so > important. I would like to see the available fast-chargers within a > radius of your location. Ah ha! What "location"? No one uses FAST chargers anywhere near their "location" (home) since the rate for FAST electricity can be FIVE to FIFTEEN times the rate from charging off-peak and/or overnight.at home. So again using such numbers would extremely bias the result for a case that almost no one uses! and is very uneconomical... Bob On Mon, Sep 28, 2020 at 4:57 PM Offgrid Systems via EV wrote: > I like the driveability quotient and how you got there. Driveability is > a far different thing to me (has more to do with the *way* the car > drives and handles), so I might call it DCR or drive charge ratio, or > Deecer for the acronym phobic. > > And I would like to see another term thrown in, since charging is so > important. I would like to see the available fast-chargers within a > radius of your location. > > This last term in your equation would be in my top 3 for buying an EV, > and it helps answer the question, can I have only one car, and use it > for long and short trips. Can I go coast to coast, border to border, and > beyond on one trip? Got 10 fast chargers within a 100 miles of your > house, and you have a Model 3, your DCR : A = 8:10 or DCR = 8 and A = > 10. Seems nerdy, now that I write it out...but it would be nice to have > more fast charger information when the average person buys a new EV. > > There is the fact that all fast chargers are not fast (I'm talking about > you Electrify America in AZ.) but hopefully we will all get to 200kw or > more eventually. > > P.S. So mine is 7.8 > > t > > -- > With hope, > > Tim Economu > > On 9/28/2020 10:58 AM, ev-requ...@lists.evdl.org wrote: > > Message: 1 > > Date: Mon, 28 Sep 2020 12:57:19 + (UTC) > > From: Mark Laity-Snyder > > To: Electric Vehicle Discussion List > > Subject: [EVDL] Drivability again > > Message-ID:<394637686.1406944.1601297839...@mail.yahoo.com> > > Content-Type: text/plain; charset="utf-8" > > > > I did include the link but it didn't show up so here is the pasted > article. > > > > There are endless factors used to compare electric vehicles (EVs) from > various manufacturers. There are 0-60 times. All-electric range (AER). > Usable kilowatt-hour (kWh) in the battery. Luggage space. Number of > seatbelts. Charge rates for DC fast charging. Efficiency. > > > > But something is missing. Something important. For the lack of a better > term, I?ll call it ?drivability.? Drivability is related to efficiency, but > it isn?t exactly that. It?s also related to charge rate, but it isn?t > exactly that, either. > > > > I would define drivability simply as how long I have to charge my car in > order to get back on the road. In terms of basic arithmetic, it could be > defined as the ratio of how quickly I can add energy to the car, to how > quickly energy is used while driving the car. > > > > To make drivability a useful metric to compare EVs, some standardizing > assumptions are required. So let?s assume that we drive the car for one > hour at 62 miles-per-hour (MPH). How long will it take to replenish the > energy used? The less time it takes to charge the car to replenish the > energy used, the more drivable the car becomes. > > > > From personal experience? > > > > My first EV was a Miata conversion. While I loved driving that car, it > had a horrible drivability factor. At 62 miles per hour (MPH), the Miata > traveled approximately 2.2 miles for every kWh consumed. Worse, its maximum > charge rate was merely 2.5 kilowatts (kW). Expressed mathematically, that > is 2.5*2.2 = 5.5, which has units of MPH. Taking it a step further, and > since the 2.2 mi/kWh efficiency assumed 62 MPH, for every hour charging, I > could drive for only 5.5/62 = 0.09 hours! As I?m defining it, my e.Miata > had a drivability of 0.09. Not good for long trips. > > > > Now I drive a Jaguar I-Pace. Its efficiency isn?t much better at 2.4 > mi/kWh at a constant 62 MPH, but its maximum charge rate is far superior at > 100 kW from a capable DC fast charger. Running through the same arithmetic > gives a driveability factor of 3.8. What this means is that for every hour > I charge my I-Pace, I can drive for 3.8 hours at 62 MPH. Those with an eye > for numbers will cry foul about now because most EVs will not sustain the > maximum charge rate on a DC fast charge for very long. But we?re going to > ignore this reality for a moment. > > > > Let?s look at one more example. I convinced my younger brother to buy a > Tesla Model 3, which has an efficiency at 62 MPH of 4.5 mi/kWh, and will > charge at 120 kW. Running through the same arithmetic gives it a > driveability of 9. Ergo, for every hour of charging one could drive for > nine hours, assuming the car?s battery and the driver?s bladder have that > type of capacity. This can also be interpreted to mean that every minute > charged enables nine
Re: [EVDL] EV Digest, Vol 95, Issue 30
I like the driveability quotient and how you got there. Driveability is a far different thing to me (has more to do with the *way* the car drives and handles), so I might call it DCR or drive charge ratio, or Deecer for the acronym phobic. And I would like to see another term thrown in, since charging is so important. I would like to see the available fast-chargers within a radius of your location. This last term in your equation would be in my top 3 for buying an EV, and it helps answer the question, can I have only one car, and use it for long and short trips. Can I go coast to coast, border to border, and beyond on one trip? Got 10 fast chargers within a 100 miles of your house, and you have a Model 3, your DCR : A = 8:10 or DCR = 8 and A = 10. Seems nerdy, now that I write it out...but it would be nice to have more fast charger information when the average person buys a new EV. There is the fact that all fast chargers are not fast (I'm talking about you Electrify America in AZ.) but hopefully we will all get to 200kw or more eventually. P.S. So mine is 7.8 t -- With hope, Tim Economu On 9/28/2020 10:58 AM, ev-requ...@lists.evdl.org wrote: Message: 1 Date: Mon, 28 Sep 2020 12:57:19 + (UTC) From: Mark Laity-Snyder To: Electric Vehicle Discussion List Subject: [EVDL] Drivability again Message-ID:<394637686.1406944.1601297839...@mail.yahoo.com> Content-Type: text/plain; charset="utf-8" I did include the link but it didn't show up so here is the pasted article. There are endless factors used to compare electric vehicles (EVs) from various manufacturers. There are 0-60 times. All-electric range (AER). Usable kilowatt-hour (kWh) in the battery. Luggage space. Number of seatbelts. Charge rates for DC fast charging. Efficiency. But something is missing. Something important. For the lack of a better term, I?ll call it ?drivability.? Drivability is related to efficiency, but it isn?t exactly that. It?s also related to charge rate, but it isn?t exactly that, either. I would define drivability simply as how long I have to charge my car in order to get back on the road. In terms of basic arithmetic, it could be defined as the ratio of how quickly I can add energy to the car, to how quickly energy is used while driving the car. To make drivability a useful metric to compare EVs, some standardizing assumptions are required. So let?s assume that we drive the car for one hour at 62 miles-per-hour (MPH). How long will it take to replenish the energy used? The less time it takes to charge the car to replenish the energy used, the more drivable the car becomes. From personal experience? My first EV was a Miata conversion. While I loved driving that car, it had a horrible drivability factor. At 62 miles per hour (MPH), the Miata traveled approximately 2.2 miles for every kWh consumed. Worse, its maximum charge rate was merely 2.5 kilowatts (kW). Expressed mathematically, that is 2.5*2.2 = 5.5, which has units of MPH. Taking it a step further, and since the 2.2 mi/kWh efficiency assumed 62 MPH, for every hour charging, I could drive for only 5.5/62 = 0.09 hours! As I?m defining it, my e.Miata had a drivability of 0.09. Not good for long trips. Now I drive a Jaguar I-Pace. Its efficiency isn?t much better at 2.4 mi/kWh at a constant 62 MPH, but its maximum charge rate is far superior at 100 kW from a capable DC fast charger. Running through the same arithmetic gives a driveability factor of 3.8. What this means is that for every hour I charge my I-Pace, I can drive for 3.8 hours at 62 MPH. Those with an eye for numbers will cry foul about now because most EVs will not sustain the maximum charge rate on a DC fast charge for very long. But we?re going to ignore this reality for a moment. Let?s look at one more example. I convinced my younger brother to buy a Tesla Model 3, which has an efficiency at 62 MPH of 4.5 mi/kWh, and will charge at 120 kW. Running through the same arithmetic gives it a driveability of 9. Ergo, for every hour of charging one could drive for nine hours, assuming the car?s battery and the driver?s bladder have that type of capacity. This can also be interpreted to mean that every minute charged enables nine minutes of driving.? The numbers discussed above reflect a maximum drivability using the maximum DC fast charging rate for a specific model. Understanding that no EV can sustain maximum charge rate when using a DC fast charger, it makes sense to be more focused on the average drivability. Over the course of a full charge, the I-Pace average charge rate at up to 90% state of charge is about 70 kW. The Model 3 is about 100 kW at up to 90% state of charge. This yields an average drivability factor of 2.7 for the I-Pace and 7.1 for the Model 3. So, what should we do with this information? I am suggesting that manufacturers start using a standardized metric similar to drivability, enabling consumers to compare different
