Driving in Circles to Test My Car

[Arthur]

I wanted to test several different things. So, I went around a 5.7-mile loop, with an elevation change of 760 feet. Starting near the top of this hill (at my house), I drove around the loop, until I was almost down to 10% (7 miles) remaining on my battery. The bottom of the loop was on level ground, with lots of stop signs/lights.

I was able to go around the loop 14 times, in about 3 hours and 15 minutes. I kept my top speed between 40 and 45 mph. My average speed for the entire trip was just under 25 mph. My trip odometer showed 80.0 miles, at 212 Wh/mi, using 17.0 kWh.

When I turned off the car, the final screen showed that I had gotten 30 miles of regen and had achieved a braking/accelerating score of 99%. Needless to say, I had driven very carefully, with gentle and gradual braking and accelerating.

I had not expected to be able to keep my average as low as 212 Wh/mi, while going up this 760-foot hill, 14 times! If pushed to its limits, the regen efficiency of the Ford Focus Electric is absolutely amazing! Keep in mind that I had the car in "Drive," not "Low." The loop that I drove on turned out to be ideal. The downhill slopes were somewhat more gradual than the uphill slopes, allowing me to minimize the amount of energy lost to regular (friction) braking.

I checked the braking regen "top ten" charts, for all of the different regions. One person has 27 miles of regen. Everone else has 20 miles or less. Granted, my trip was somewhat contrived, but it was still real-world driving conditions, with no car-sized treadmills involved. ...and my 30 miles of regen probably won't ever show up, because my car is currently unable to connect to MyFordMobile.

The other motivation for using up a full battery charge, yesterday, was so that I could compare the amount of energy used by the car to the amount of energy used to recharge the car and watch to see if the charging efficiency varied from the beginning of the charging process to the end. It did not.

I currently use a 110-volt outlet to charge my car. I have a TED (The Energy Detective) whole-house, energy-monitoring system, with a separate monitor that allows me to isolate the breaker that the car is using to charge. I actually kept track of the time when I started charging the car and the times it reached 25%-charged, 50%-charged, 75%-charged, and 100% charged. Yes, that means that I did my best to predict when it would reach each of those points, then I stood and stared at the blue light, until the flashing quarter of the ring stayed on and the next quarter started flashing.

The grand result of this massive waste of time: The energy-efficiency of charging the car on a 110-volt circuit is between 72% and 73% (in cool, but not cold, weather). ...and each quarter of the battery-charging sequence has the same efficiency. A secondary result is that the part of the battery capacity that you are allowed to use and charge back up (from a completely discharged battery, up to the point where the blue light, around the charger, finally goes out) is between 19.20 and 19.25 kWh. The battery usually (always?) continues to charge, after the light has gone out. I unplug mine, immediately after the blue light goes out, because that leaves me just enough capacity to capture regen, on my way down the hill, in the morning. However, leaving it plugged in seems to "top off" the battery, but probably does so at a very low efficiency. (It continues to draw the same amount of power, for an extended period of time, while the battery obviously no longer has the capacity to store more than a small fraction of that energy.) At this point, I'm not sure if this "topping off" behavior is a "bug" or a "feature," of the car's software. In any event, it's very wasteful! ...and it's not "conditioning your battery," during this time. Conditioning should require much less power than charging!

Finally, I wanted this test to help me understand more about the "fuel economy" and range of the FFE. The EPA fuel economy rating of 105 MPGe (in combined driving) seems to be an attempt to incorporate the total cost of CHARGING the FFE. If this fuel economy rating were based purely upon the number of miles travelled per kWh of energy DISCHARGED from the FFE's battery, it would be 131 MPGe (which is 257 Wh/mi, as reported by the car). ...but it seems that only applies, if you're using a 220-volt charging station (which I've heard are about 80% efficient). For charging done on a standard 110-volt outlet, the COST-BASED fuel economy is 95 MPGe (131 X 0.725). That would have been useful information to know, when I was deciding NOT to buy a 220-volt charger, for my home.

IMHO, the "total cost per mile" info is useful, but should not be mixed in with the fuel economy and range estimates. Let's remember that these "EPA" numbers are often simply "provided to" the EPA, by the auto companies. Tell me if I'm crazy, here, but I think that the "fuel economy and range estimates" are totally meaningless, unless they represent the fuel economy that a driver would have to achieve (as displayed on the car's screens), in order to be able to drive a certain distance (the range). In other words, the "fuel economy" number and the "range" number should be determined by the same TEST TRIP!!!, at the same TIME!!! After all, that's what customers want to know: a typical fuel economy number, that is achievable by a typical driver, in typical driving conditions, AND the CORRESPONDING RANGE that the driver will experience, when the driver achieves that typical fuel economy.

So, the FFE's window sticker SHOULD SAY that you must achieve 131 MPGe, if you want to go 76 miles, on a single battery charge. It is deceptive to say that the fuel economy is 105 MPGe, a number which is calculated by including (in the denominator) the energy lost, during the charging process. That's like calculating the fuel economy of a gasoline-powered car, by including the gasoline that spilled on the ground, when the pump was accidentally allowed to overflow the car's tank. It's deceptive.

The main reason that it's deceptive is that it allows the car companies to INFLATE THE RANGE of their fully-electric cars. If you announce that a 105-MPGe (321-Wh/mi) car has a range of 76 miles, you are effectively telling prospective customers that a range of 76 miles is EASILY achievable and that, under optimal circumstances, they can probably achieve about 1.5X that range (114 miles!!). That is what I expected, based upon the information given. It is NOT an unrealistic expectation, either. Consider the range that actually CORRESPONDS to a fuel economy of 105 MPGe: 61 miles!

If we actually drive recklessly enough to only get 105 MPGe, we will be limited to a range of 61 miles. As for achieving 1.5X the "typical" range of the FFE, I have just proven that it is possible. Yesterday, I went 80.0 miles on 17.0 kWh, in a car that seems to have a maximum usable battery capacity of AT LEAST 19.25 kWh. When driving the way that I did, yesterday, anyone should be able to achieve 1.5X the actual 61-mile range of the FFE: 91 miles.

(80.0 miles) X (19.25 kWh / 17.0 kWh) = 90.6 mile

However, contrary to the false advertisement on the FFE window sticker, 76 miles is NOT a TYPICAL range for the FFE. A 76-mile range does not correspond to a fuel economy of 105 MPGe. A 76-mile range actually corresponds to a fuel economy of 131 MPGe, which is already much more efficient driving than is TYPICAL. So, it is not possible to improve upon it, as much as it WOULD BE possible to improve upon a fuel economy of 105 MPGe.

There are only 4 ways to exceed 91 miles of range, on the FFE: 1) Never exceed a speed of about 15 mph, 2) Drive down a big mountain (but don't let anyone see you drive back up), 3) Only drive your car on a car-sized "treadmill," or 4) Get confused between actual range and "projected" range, in the FFE.

 

[ashuri]

I haven't (yet) really figured out the "projected" vs actual range, I know once the car said I had 86 miles of range but I was sure I couldn't drive that far really(?).

I guess your I would say scientific approach to this gives us a few food for thought:

1) Actual and projected range vary by about 15%
2) In an ideal world we would all drive around 35 or less MPH to maintain "ideal range"
3) Ford made a heck of a car that can be driven for quite some time in an otherwise "less than ideal" conditions

With that said I applaud your work...now let's see if the people at Ford are listening to all this!

 

[WattsUp]

People might misunderstand what the EPA's estimated Wh/mile corresponds to, but I see no evidence that anybody is "inflating" range numbers. It can be confusing, but everything makes sense if you work it through.

The estimated mileage for FFE reported by the EPA is relative to the energy required to charge the car. This is a key point to understand, otherwise the mileage estimate won't make sense. The EPA has no idea how the car or its charger works internally, no does the EPA know or care what the FFE's dashboard says. The EPA reports only what can be observed and measured externally to the car. Namely, the energy supplied in order to fully charge it and the distance it can then drive under typical operation.

The EPA has also determined (generically, for all cars) that 1 gallon of gasoline is equivalent to 33700 Wh of electrical energy. So, when the EPA estimates 105 MPGe for the FFE, what they are really stating is that, for every mile driven, the FFE must be supplied with 320 Wh of energy (since 33700 Wh / 105 MPGe = 320 Wh/mile). This same number is reported on the FFE window sticker, stated in the form "32000 Wh per 100 miles", right alongside the 105 MPGe estimate. Both are simply different expressions of the same information.

If the EPA reports that the FFE is able to drive 76 miles on a "full battery", we can conclude that the total energy required to fully charge the FFE must be 24320 Wh (since 320 Wh/mile * 76 miles = 24320 Wh). But, we also know that EV charging is, on average, only about 80% efficient (sometimes more, sometimes less, but about 80% on average). The rest is wasted as heat (and this is why the process is not perfectly efficient, it induces a chemical reaction that generates heat in addition to storing a charge). With this, we can further conclude that, of the total 24320 Wh required to fully charge the FFE, it will only actually be able to store 19450 Wh in the battery (since 24320 Wh * 0.8 = 19450 Wh).

While this figure of 19450 Wh of "actual stored energy" is merely something that we have deduced from the original EPA mileage estimate, it does make very good sense. We know the advertised total battery capacity of the FFE is 23 kWh (or 23000 Wh). We also know that, in order to prolong battery life, the industry practice is to use only 85% of the total battery capacity. Assuming this is true of the FFE, the deduction of 19450 Wh lines up quite nicely, as 19450 Wh is just about 85% of 23000 Wh.

We also know that driving around in an FFE at 50-60 mph (which, IMO, one could reasonably call "typical operation") consumes about 250-260 Wh/mile from the battery (according to the FFE itself). So, assuming an average discharge rate of 255 Wh/mile and total stored energy of 19450 Wh, how far can we expect to drive in an FFE under those conditions? It should come as no surprise that the distance is 76 miles (since 19450 Wh / 255 Wh/mile = 76 miles).

Making some educated assumptions and doing the math, I find no evidence whatsoever that Ford or the EPA has mislead anyone as to typical range of the FFE. In my own personal experience, I achieve 76 miles quite easily, usually more. I employ a mix of slow (35-45 mph) and fast (55-65 mph) driving. When I fully charge my FFE, my own measurements show that, on average, just over 24000 Wh of energy is required (just as deduced above). All of the typical driving I do in my FFE, mile for mile, requires me to purchase about 320 Wh/mile from my electric utility (just as the EPA estimated I would need to). And I am perfectly happy with this. Thrilled, in fact. For me, my FFE performs exactly as advertised.

 

[dmen]

The grand result of this massive waste of time: The energy-efficiency of charging the car on a 110-volt circuit is between 72% and 73% (in cool, but not cold, weather).

Yeah, that's pretty similar to what I'm getting using the trunk cord. I've seen a bigger range of 60% to 76%, with the lower efficiency in cold weather when I'm sure the thermal management was using wall power to keep batteries warm as well as to charge them up.

Finally, I wanted this test to help me understand more about the "fuel economy" and range of the FFE. The EPA fuel economy rating of 105 MPGe (in combined driving) seems to be an attempt to incorporate the total cost of CHARGING the FFE. If this fuel economy rating were based purely upon the number of miles travelled per kWh of energy DISCHARGED from the FFE's battery, it would be 131 MPGe (which is 257 Wh/mi, as reported by the car). ...but it seems that only applies, if you're using a 220-volt charging station (which I've heard are about 80% efficient). For charging done on a standard 110-volt outlet, the COST-BASED fuel economy is 95 MPGe (131 X 0.725). That would have been useful information to know, when I was deciding NOT to buy a 220-volt charger, for my home.

I do think it's questionable that the EPA numbers are based on charging at level 2 (80% charging efficiency) when the car doesn't come with a level 2 charger. If they're going to incorporate charging inefficiency in the calculation for fuel economy, they should test the vehicle as equipped, so as charged by level 1, as your drive to nowhere did.

IMHO, the "total cost per mile" info is useful, but should not be mixed in with the fuel economy and range estimates. Let's remember that these "EPA" numbers are often simply "provided to" the EPA, by the auto companies. Tell me if I'm crazy, here, but I think that the "fuel economy and range estimates" are totally meaningless, unless they represent the fuel economy that a driver would have to achieve (as displayed on the car's screens), in order to be able to drive a certain distance (the range). In other words, the "fuel economy" number and the "range" number should be determined by the same TEST TRIP!!!, at the same TIME!!! After all, that's what customers want to know: a typical fuel economy number, that is achievable by a typical driver, in typical driving conditions, AND the CORRESPONDING RANGE that the driver will experience, when the driver achieves that typical fuel economy.

I half agree with you. I think the fuel economy or MPGe has to do with financial cost, so basing it on energy needed to charge is fine. But the sticker should clearly state so, and should reflect the efficiency of level 1 charging unless they start making a level 2 EVSE standard equipment. But fuel efficiency or Wh/mile listed should reflect car only, since that's what a driver is going to use to determine their unique driving pattern's corresponding realistic range. EPA expected range would then follow from fuel efficiency. Of course on the sticker that's not how it works, as you know.

So, the FFE's window sticker SHOULD SAY that you must achieve 131 MPGe, if you want to go 76 miles, on a single battery charge.

I don't think it should say you must achieve 131 MPGe to go 76 miles, because how the heck do you know how many MPGe you're getting while driving? It's almost a nonsense number for driving purposes. IMHO the vehicle sticker should say that you must achieve 257Wh/mile if you want to go 76 miles. Same thing, but with a number that the driver can use.

The main reason that it's deceptive is that it allows the car companies to INFLATE THE RANGE of their fully-electric cars. If you announce that a 105-MPGe (321-Wh/mi) car has a range of 76 miles, you are effectively telling prospective customers that a range of 76 miles is EASILY achievable and that, under optimal circumstances, they can probably achieve about 1.5X that range (114 miles!!). That is what I expected, based upon the information given. It is NOT an unrealistic expectation, either. Consider the range that actually CORRESPONDS to a fuel economy of 105 MPGe: 61 miles!

I don't agree that the range is inflated, any more than the MPG on any nonelectric car is inflated. In fact the range is less inflated than MPG was on any gas car we've bought. Does anyone expect to get better than an gas car's listed highway MPG? I certainly don't. FFE's web FAQ says cautiously, "Depending on your driving conditions, Focus Electric can go up to 76 miles on a single charge." But I can predictably get better than FFE's listed range.

However, contrary to the false advertisement on the FFE window sticker, 76 miles is NOT a TYPICAL range for the FFE. A 76-mile range does not correspond to a fuel economy of 105 MPGe. A 76-mile range actually corresponds to a fuel economy of 131 MPGe, which is already much more efficient driving than is TYPICAL. So, it is not possible to improve upon it, as much as it WOULD BE possible to improve upon a fuel economy of 105 MPGe.

I have to disagree with you here. 76 miles is achievable driving typically. You looked at the records for regen miles in a single trip on MFM, right? Surely you've looked at the records for longest distance on a single charge. In my area there are several Ford test cars taking up the top spots, but real drivers go more than 100 miles on a charge. The thing that isn't obvious is that those aren't open highway drives going 100 miles- those are more likely something like four 25-mile, med-heavy highway traffic and surface road trips on the same day. When I'm commuting ~20 miles round trip in rush hour in nice weather, averaging 10-15 mph, I see 180-200Wh/mi and if I continued to drive that way for 1-2 hours a day over 1-2 weeks without plugging in, I absolutely would go further than 100 miles. This is "typical driving" for me. Maybe something closer to other people's typical: when I drive 55 mph on a flat open highway, I see about 240Wh/mi. Doing mostly highway like that, and about 15 miles of surface streets, I have driven just over the EPA 76 mi range a few times, with 10% battery capacity remaining. (The EPA highway efficiency of 99MPGe corresponds to vehicle efficiency 272Wh/mi, for reference).

There are only 4 ways to exceed 91 miles of range, on the FFE: 1) Never exceed a speed of about 15 mph, 2) Drive down a big mountain (but don't let anyone see you drive back up), 3) Only drive your car on a car-sized "treadmill," or 4) Get confused between actual range and "projected" range, in the FFE.

To be fair, driving at a constant speed of 40 mph takes about 200Wh/mi in my experience, which would get you further than 91 miles.

 

[Arthur]

I haven't (yet) really figured out the "projected" vs actual range, I know once the car said I had 86 miles of range but I was sure I couldn't drive that far really(?).

I guess your I would say scientific approach to this gives us a few food for thought:

1) Actual and projected range vary by about 15%
2) In an ideal world we would all drive around 35 or less MPH to maintain "ideal range"
3) Ford made a heck of a car that can be driven for quite some time in an otherwise "less than ideal" conditions

With that said I applaud your work...now let's see if the people at Ford are listening to all this!

Ashuri: My 5.7-mile route was about 1/3 downhill, 1/3 level terrain (in town), and 1/3 uphill. During my 14 "laps" around the same route, I saw my "Projected Range" (hereafter referred to as "PR") do some really weird things. On the first lap, I picked up about 22 miles of PR, which peaked just before I started going back up hill. Then, I lost 22 miles of PR, as I went back up the hill. After several laps, I noticed that I was gaining (and losing) about 35 mi of PR, on each lap, and most of the gain was occurring, not during the downhill stretch, but, instead, during the last third of the level stretch. In the last few laps, I was gaining and losing 50 or 60 mi of PR, always gaining most of it during the last part of the level stretch, but, now, the PR was sometimes making instantaneous upward jumps of 5 or 10 miles, and even continuing to increase on the first part of the uphill stretch (which is fairly steep).

On the final lap, my PR dropped to 8 miles, shortly after passing the highest point, and starting downhill. At the bottom of the hill, it was still only at about 20 miles and increasing only gradually, as I drove through town, on level ground. Then, in the last 3/4-mile of level ground, the PR started climbing like crazy, and didn't peak until I was 1/4 of the way up the hill. It peaked at 92 miles of Projected Range!!! Then, less than 2 miles later, I was parked in front of my house, with a mere 7 mi of PR remaining. That's right. I lost 85 miles of PR, in less than 2 miles!

Explain that!

Ford is obviously using SOME sort of algorithm, to calculate PR, but the algorithm does very poorly under highly variable conditions of terrain or speed, and is especially inaccurate, when you have varying conditions AND your battery is low (just when you need an accurate prediction the most).

For the most part, I ignore the PR number and try to stay focused (no pun intended) on the battery-shaped graphical "fuel gauge," which I am planning make a kWh scale for. If I can print it out just right and cut it out, I will tape it down, next to the "battery." Then, I will create my own "mental algorithm," working backward from my house, keeping in mind how many kWh it takes to go up my hill, how many it takes to go through town to reach the bottom of the hill, and how many kWh it takes for the first part of my trip, at highway speeds.

That is just an example, but if I have a simple chart of the different types of driving/speed/terrain, and the corresponding Wh/mi, I should be able the estimate whether I have enough kWh to make a trip with those particular highway, city, and uphill segments. In the future, perhaps Ford can do this FOR US, by simply integrating (into our Nav system) the same kind of speed limit and terrain data (not to mention traffic predictions) that exists on mapping websites, like Google Maps and MapQuest.