Monday, January 25, 2016

SparkEV range

What is the driving range for SparkEV? Well duh, it's 82 miles. EPA tells us so. But is it really? When I was driving gas cars normally, I was almost always getting less MPG than EPA figures. When I "hyper miled", a term for driving technique for maximum fuel efficiency, I was getting far more than EPA figures. In this post, we'll explore some aspects of driving range and why they are not simple.

Maximum range

A common question asked when people see me driving an EV is "what's the longest range you get?" The standard answer is 82 miles per EPA, but the true answer is more complicated. It is so very easy to hypermile with EV and get far more range, especially under favorable conditions. Below is a screen shot of a short drive under very favorable condition.

Excuse the dusty image; dog hair and their dust are hard to keep off plastics. SparkEV has 19kWh battery of which some less is usable. Let's assume 90%, or 17kWh. Then the maximum range would be

51.1 mi/kWh * 17 kWh = 869 miles
51.1 mi/kWh * 33.7 kWh/gal = 1722 MPGe

I probably could've done better if not for couple of stop lights. It shows that 82 miles EPA range depends on conditions with which the EV is driven. How did I achieve this phenomenal efficiency? It was mostly down hill, though I kept up with traffic.

You might argue that same condition would result in infinite miles of range in gas cars due to downhill coasting, but that isn't the case. You still have to come to a stop, accelerate on green light, and keep up with traffic. Even if gas car coasts, they still have to apply the brakes eventually, giving up energy as heat while EV with regenerative braking would add energy into the battery upon braking. In fact, it would be possible for EV to have more energy at the end of "coasting" whereas gas car would always lose energy, even for tail light when the brakes are applied. While infinite miles on gas car is not possible, "greater than infinite" miles is possible with EV given enough long downhill.

Therefore, maximum range on SparkEV is infinite miles!

No really, what is the maximum usable range per battery charge?

Obviously, we can't always drive downhill. Then how far can SparkEV drive on a charge? Someone actually drove for entire battery charge at favorable driving condition (flat road, low speed), and achieved almost 140 miles!

So the practical upper limit on 2014 SparkEV is about 140 miles per charge. What the driver did was to drive at 24 MPH, lowest possible speed for cruise control, for about 6 hours. At low speed, EV does extremely well. Why not gas cars, too? We'll explore that later in this post.

Something interesting from his experiment is the miles/kWh achieved: 7.3 mi/kWh. That translates to 246 MPGe. To drive 140 miles at 7.3 mi/kWh would need

140 miles / 7.3 mi/kWh = 19.2 kWh (2014 SparkEV usable capacity)

But he was driving 2014 SparkEV with bigger battery (21 kWh) than 2015 model. The total usable battery of 2014 SparkEV is 91.3% of full battery capacity of 21 kWh. If we assume the same percentage of battery capacity is used in 2015 SparkEV with 19 kWh battery, the usable battery capacity would be

19 kWh * 91.3% = 17.4 kWh (2015 SparkEV usable capacity)

The assumption I made above of 17kWh of usable battery capacity isn't far off.
If we assume same power is needed to drive 24 MPH for 2015 model that has 17.4 kWh usable battery, the maximum range would be

17.4 kWh * 7.3 mi/kWh = 127 miles

But 2015 SparkEV is lighter by about 80 pounds as well as having lower gearing that's better for low speed (3.17 in 2014 vs 3.87 in 2015). While the usable battery capacity is just an estimate, it does give you an idea that the maximum driving range of SparkEV is around 130 miles when driven at 24 MPH, probably closer to 140 miles.

What range do you get for your driving?

Above examples are under pretty optimistic scenarios. Typical driving would be far different. But what is typical? We can classify freeway and combined. Living in SoCal, it's hard to avoid the freeway and just drive local, so local only figure isn't available in my experiment.

For freeway driving, I have 55 MPH figure from previous post: 84.7 miles driven with 9 miles remaining  = 93.7 miles.

Strictly keeping at 55 MPH with windows closed and no AC/heat, one can expect bit over 90 miles range. Obviously, this is only possible in certain times, and not in summer heat or in rain (wipers, rain drop force, etc).

At this point, let's check our results. Assuming 17 kWh usable battery capacity and 5 mi/kWh at 55 MPH, the maximum range would be

5 mi/kWh * 17 kWh = 85 miles

What!?!? How did 93.7 miles come about? Going the other way,

93.7 miles / 5 mi/kWh = 18.74 kWh

Hmmm. Something must be wrong. Indicated range is based on almost 100% of battery capacity? While it's possible, more likely is that I misread "short section of flat road" power reading; 10% off might be 10kW, and it could be possible that I was going slight uphill. In any case, 17 kWh usable battery capacity for 2015 model will be assumed based on experiment from 24 MPH for 2014 model with 21 kWh.

Then what would be mi/kWh for driving 93.7 miles with 17 kWh?

93.7 miles / 17 kWh = 5.5 mi/kWh

Wow, that seems incredible. I think 17 kWh usable capacity makes more sense. Furiously waving my hands, let's just say that SparkEV range at 55 MPH is about 90 miles.

What range do you get for your combined driving?

More typical would be combined driving over long distance. I have kept my trip meter running since getting the car. The driving includes about a dozen 300 miles per day all-freeway trips using multiple DCFC as well as uphill, downhill, local, country road, city slicker havens, stuck in traffic. Below image shows the current mi/kWh.

At 5.1 mi/kWh, 17 kWh would result in

5.1 mi/kWh * 17 kWh = 86.7 miles

That's slightly better than EPA estimate of 82 miles. But if we assume almost 100% capacity is used as suggested by 55 MPH experiment,

5.1 mi/kWh * 18.74 kWh = 95.6 miles

That's when the battery is fairly new. What happens as the battery degrades? This is just a guessing game, but let's assume 20% degraded after 3 years, with average of 15% driven at degraded state. Because the battery capacity initially diminish as exponential decay, degradation would slow down as time goes on, which means one would spend longer time in more degraded state. But remember, this is just a guess as far as actual numbers are concerned.

19kWh * 85% = 16.15 kWh
5.1 mi/kWh * 16.15 kWh = 82.4 miles

Well, well, what do you know? We're right at EPA estimated range when battery capacity degradation is taken into account. I don't know if this is what Chevy and EPA had in mind when they came up with the range estimate. It sure as heck doesn't make sense to use EPA MPGe figure to derive the range. Using 17kWh as usable battery capacity and 80% charger efficiency, it works out to

119 MPGe / 33.7 kWh/gal * 17 kWh / 0.8 = 75 miles.

Therefore, telling people that SparkEV typically gets 82 miles per charge is accurate, despite the EPA discrepancy.

Experimental range summary

Range can be summarized as follows. All are with new battery with 2015 SparkEV and using actual experimental data.
  1. 85 miles under typical conditions, summer and winter, and mostly with windows down (even in freeway) and dogs sticking their heads out.
  2. 90+ miles at 55 MPH windows up with slight elevation gain (about 500 ft).
  3. 130 miles at 24 MPH flat road without stopping.
  4. 869 miles in some long stretches of downhill, even with some traffic lights.
  5. Greater than infinite miles (?) for very long downhill.
Power vs speed: theory vs practice

It's good to know the range based on actual driving, but it's not possible to experiment at different speeds. For example, we know the range would be less if driven at 90 MPH than at 55 MPH. But I don't have the luxury of long drives at 90 MPH on flat ground; there is vast government conspiracy to take away my driving license, even when I'm not exceeding the speed limit (I was nowhere near 186,000 miles per second!).

I have to use short sections of flat road to test at lower speed. At 30 MPH, it was between 3kW and 4kW. At 55 MPH, it was almost solid 11kW. At 60 MPH, it was roughly 13kW to 14kW. Using these data points, we can construct a model for SparkEV power vs speed. Then we can figure out how much power is consumed at particular speed, and calculate the range as if it was driven at that speed.

According to Physics, power required to overcome aerodynamic drag is proportional to cube of speed. Power required to drive at 60 MPH would be 8 times the power required to drive at 30 MPH (twice the speed, 2^3 = 8 times the power). But the data I collected show only 4 times the power at 60 MPH. Physics is wrong?

Physics isn't wrong. We must also add other resistance. Tires are not friction-less, bearings, and all the moving parts contribute to some force resisting motion. As a simple model, force required to overcome "rolling resistance" is proportional to weight. Little detour in Physics lesson: That means the energy is also proportional to weight to drive the same distance (Work = Force * distance). Since the weight does not change, energy spent is constant at constant speed. But the rate of change of energy (power) is linearly related. Therefore, power needed to overcome this weight related friction is linearly increasing with speed.

But wait, there's more! When the car is "on", it is using power, whether it's the day time running lights or the radio. This power is constant regardless of speed, unless you start to mess with AC/heat or blasting the radio.

And then even more! At different power levels, current drawn would be different, but it would still go through same diameter wires. Higher current would increase electrical losses. This is not easy to quantify with the data we have. However, one can guesstimate this by looking at other electronics circuits. I use switching regulator as a model for this, which is about 90% efficient in operating range, much less in extreme low and high currents. This is also my motor efficiency (Engine efficiency).

tps54040a (42V in switching regulator)
Now we can go and do bunch of calculations to figure out the relationship between power vs speed by combining the parameters, or we search the Internet to do that for us. If we plug in the right parameters, there are web sites that give us very nice summary of calculations. Here's an excellent web site that does exactly that. The link below has all the parameters to produce the data for SparkEV.^2&FuelWh=33557&IceEfficiency=.9&DrivetrainEfficiency=.95&ParasiticOverhead=500&rho=1.225&FromToStep=5-200-5

Since not all values are available from the <sarcasm>extremely technically informative SparkEV user manual</sarcasm> following are some common values found on the Internet.

Weight (lb): 3000 lb (google)

Coeff. of rolling resistance (Crr): 0.01 (, tire on asphalt)

Drag coefficient: 0.326 (

Frontal area (sq ft): 8.8 / 0.326 = 27 sq ft ( gives drag area, divide by drag coefficient gives frontal area.)

Fuel energy density (Wh/gal): 33557 (summer blend drop down option)

Engine efficiency: 0.9 (guess based on switching regulator)

Drive train efficiency: 0.95 (guess; default value)

Parasitic overhead: 500 (lights are about 250 Watts, double it as guess)

Air density: 1.225 (default value)

Then it spits out a nice table. I reproduce just from 0-90 MPH, maximum speed of SparkEV and few more. I added the last column which shows the range assuming 17kWh battery capacity.

Yellow highlights the key data to be discussed. Green cells are actual experiment data that match the calculations. As you can see, 30 MPH is between 3kW and 4kW, 55 MPH is bit above 11kW, 60 MPH is between 13kW and 14kW, close to what was observed. This tells me the parameters found are pretty close to actual values.

Range data analysis

Again, let's assume the battery capacity of 17 kWh. Something to keep in mind is that these are just estimates. For example, the motor may not hold 90% efficiency throughout the speed range. Still, it gives some indication of what SparkEV ranges could be.

At 25 MPH (2.7 kW), it would be good for 6.3 hours of driving, which would be 25*6.3 = 158 miles range. In the experiment above, the driver only reached about 140 miles. Was he overweight? Did he make some stops? Did he slow down? More likely, the parameters I use are not exactly what he had. His experiment was with 2014 model which was about 80lb heavier as well as larger battery than 2015 model. To achieve close to 140 miles, one would have to drive between 30 MPH and 40 MPH. Still, that's close enough for this exercise.

We can evaluate EPA figures as well. EPA range is 82 miles. From the table, that range is achieved when driven at constant 55 MPH. Unfortunately, this includes all driving conditions, not just the highway. Then we turn our attention to EPA's MPGe which separates city and highway.

EPA rates SparkEV as 119 overall (between 60 MPH and 65 MPH from table), 128 city, and 109 highway. While city figure is complicated due to multiple stops one has to consider, the highway figure is presumably based on much simpler driving dynamics. From the table, we can see that 109 MPG is reached at speed bit above 65 MPH. I suspect it was closer to 65 MPH with the heavier 2014 model of SparkEV. Also of significance at 65 MPH is the range of about 65 miles. Considering one doesn't drive to empty battery, actual range would be less, maybe 55 to 60 miles.

An interesting aside is the theoretical maximum speed of SparkEV. While SparkEV is electronically limited to 90 MPH (and saving me from getting my license taken away... again!), ecomodder web site shows all the way to 200 MPH. SparkEV is capable of 100kW, and the speed at which 100kW is needed is over 125 MPH. Without electronic limit, that's the absolute maximum speed. At that speed, the range would be only 22.3 miles. Taking some margins into account, usable range would be 12 to 17 miles.

But SparkEV may not sustain 100kW for very long. The longest known sustained battery use is 48 kW at DCFC. 51 kW is used at 100 MPH, 45 kW at 95 MPH. Well, 95 MPH close enough to 90 MPH with some margin, and that's probably why SparkEV is electronically limited to 90 MPH. At 90 MPH, range would be only 40 miles. Taking some margins into account, usable range would be 30 to 35 miles.

In summary, the maximum range for SparkEV on flat road is between 40 miles (90 MPH) and 150 miles (25 MPH, lowest speed limit in most of US). Note that all of these values are with windows closed, no heat / AC, just simple driving at constant speed on flat road. Range will be less for any additional drain on the battery, such as two 150lb dogs sticking their heads out the window. In addition, maximum range should be de-rated to take into account some margin; 10 miles is a reasonable number. Then the usable range is between 30 miles (90 MPH) to 140 miles (25 MPH).

Screw it. It's all just too messy. Just say it's 82 miles.

Is 1000 miles per day using DCFC possible?

Previously, I wrote a blog post that 1000 miles per day using DCFC is possible.

But is it really? Now that we have better range estimates, we can do some checks to debunk (or validate) the assertions. I'm using 17 kWh as maximum battery capacity. 80% of that is 13.6 kWh. Knowing at 12% to 89% took 13 kWh in 20 minutes, 13.6 kWh in 20 minutes starting at lower state of charge may be possible. Adding 5 minutes to get off the freeway and and another 5 minutes to get back on, total time for DCFC is 30 minutes.

Driving at 65 MPH, the range is 66 miles. 80% of that is 53 miles. Time to drive is 0.82 hours (53/65). Adding 0.5 hours for DCFC equals 1.32 hours. 53 miles / 1.32 hours = 40 MPH average. 24 hours of this would be 964 miles. It's close, but not quite 1000 miles in a day.

Doing the same with 55 MPH (83.3 miles range, 80%=67 miles, 1.2 hours drive + 0.5 DCFC = 1.7 hours, 39 MPH average), result is 934 miles, less than 65 MPH case.

Doing the same with 70 MPH (59.4 miles range, 80%=47.5 miles, 0.63 hours drive + 0.5 DCFC = 1.13 hours, 42 MPH average), result is 1006 miles. So it is theoretically possible to drive over 1000 miles in a day at 70 MPH using 21 (24/1.13) DCFC sessions. I'm not crazy enough to try this, but I'm sure there are loons out there.

Edit: 2016-10-20

Someone drove over 1000 km in one day (16 hours) with SparkEV! That might be one day distance record for SparkEV. Below is the video.

Below is the discussion. It's in French since he's in Canada (yes, they sell SparkEV in Canada, Mexico, and Korea), but you can use google translate to view in any language.

It works out to 1050 km (650 miles) in 16 hours, which is 65.6 km/hr (40.6 MPH) on average. Had he driven 24 hours in same pattern, he would've driven 1575 km (975 miles). Such feat would not be possible with slower charging EV like Nissan Leaf (24 kWh version) or EV without DCFC like Fiat 500e.

So for now, the real world range of SparkEV per day is 1050 km (650 miles) while leaving 8 hours for sleeping and extrapolated 1575 km (975 miles) in 24 hours without sleeping.

SparkEV theoretical worst case

Above analysis is a typical case using values that match the experimental data. Now let's explore the worst case. I don't mean turn up the heater and open the windows. I mean things like changing the tire to less efficient model or the motor/battery has worse efficiency due to age.

Worst case rolling resistance for tire on asphalt from Wikipedia is 0.15, probably when using super wide tires. Who knows? Someone may want to install Corvette rims and tires on SparkEV. Some people are insane as Tesla appropriately name their driving mode.

We guessed engine efficiency to be 90% (bit less than DCFC), but it could be less especially with aging battery and not-as-well lubricated motor and gears. Using 80% as engine efficiency, the same as L1 charging efficiency, we get the following.^2&FuelWh=33557&IceEfficiency=.8&DrivetrainEfficiency=.95&ParasiticOverhead=500&rho=1.225&FromToStep=5-200-5

To save you the trouble, below is the screen shot of the table for worst case.

Well, it's not so bad. At 55 MPH, the range is only 72 miles vs 83 miles above. At 65 MPH, the range is only 59 miles vs 66 miles above. Still, it's only about 10% worse. I can live with that if the replacement tires cost $100 less.

SparkEV Conclusion

SparkEV gets about 85 miles of range per charge, but that's with new battery and without any margin. With margin, it's more like 75 miles range. Under low speed conditions, it would get far more miles per charge, as much as 140 miles at 25 MPH. For city driving and stuck in traffic, it should get much better than EPA estimate. It's simple to have longer range on SparkEV; just keep the speed low, but above 15 MPH. Using multiple DCFC sessions, even 1000 miles per day may be possible at 70 MPH or more.

SparkGas theoretical analysis

For SparkGas, major differences are weight and engine efficiency. Although SparkGas has grill opening that increases drag, we ignore that for this exercise to give benefit to gas car. What we are after is close to EPA highway MPG number of 39 MPG at 65 MPH by tweaking the engine efficiency number. Why 65 MPH? Because SparkEV's highway EPA MPGe figure matched at 65 MPH.

Because gas car is so messy in terms of efficiency, not only does it vary efficiency through RPM but braking wasted as heat, highway MPG is best we can hope for in this comparison. Multiple iterations of tweaking engine efficiency to make 39 MPG at 65 MPH result in engine efficiency of 30%. Then the following parameters are used.

Weight (lb): 2300 lb (google)

Coeff. of rolling resistance: 0.01

Drag coefficient: 0.326 (same as SparkEV, though probably worse with SparkGas)

Frontal area (sq ft): 8.8 / 0.326 = 27 sq ft (same as SparkEV)

Fuel energy density (Wh/gal): 33557 (summer blend drop down option)

Engine efficiency: 0.3 (trial and error; see above)

Drive train efficiency: 0.95 (default value)

Parasitic overhead: 500 (lights are about 250 Watts, double it as guessed figure)

Air density: 1.225 (default value)

To save you the trouble, below is the screen shot of the table.

One thing that jumps out at you is 107 MPG at 15 MPH. Yeah, this is total bogus. SparkGas will not achieve anywhere close to that. The problem is that gas engine efficiency is not a constant but varying over RPM with only a narrow range tuned for best efficiency AT FULLY OPEN THROTTLE. Typically, the maximum engine efficiency is about 75% of full power. With SparkGas having 98 HP, 75% would be about 75 HP. At that power, it would be going way over 90 MPH, probably even way over 100 MPH. While the engine efficiency might be maximum, it would get awful MPG due to aerodynamic drag.

Therefore, getting meaningful theoretical data is far more difficult with gas car; one has to know the engine efficiency at particular speed (that also varies by gears). Getting that data may be possible, but I won't bother. Gas cars suck!

So how do you maximize efficiency on a gas car? Fully open the throttle (minimize pumping loss) to reach maximum engine efficiency (about 75% of red line) beyond the speed limit, then shut off the engine to coast to below speed limit, then repeat. This is called "pulse and glide", a practice that should be avoided (just get an EV!)

Another is to simply get smaller engine (ie, less powerful). Then it's more likely to have reasonable highway speed matched to efficient engine RPM. This is why old Geo Metro (55 HP) and new Mitsubishi Mirage (74 HP) are so efficient, but they are very boring with 0-60 MPH time of over 12 seconds. Again, just get SparkEV for maximum fun and efficiency.

Hoping for SparkEV 2.0

With GM having used up half the $7500 federal EV tax credit even before first Bolt rolls off the assembly line, it's doubtful they'll continue or expand SparkEV sales. SparkEV costs $12K less than Bolt, and even with same percentage profit margin, Bolt will make more money for GM. Having SparkEV eat into tax credit at same level as Bolt makes no sense. Well, at least that would be the bean counter's argument, which I completely understand.

But I can hope and dream, can't I? Suppose there could be SparkEV 2.0, how would I go about it? Previously, I showed that longer range doesn't have to mean bigger battery. I stated SparkEV with drag coefficient of 0.15 (like 1930's prototype car) would yield close to 180 miles range while charging 140 miles in 20 minutes using existing 50 kW charger.

But of course, that's wrong; that ignored the rolling resistance and static power requirement. So let's explore several cases to see what is possible: Drag coefficients of 0.24 (Tesla S, Prius), 0.22 (half way between EV1 and Tesla S), and 0.15.

First is the case of 0.15 to debunk my own erroneous assertion.

Well, the range is only 110 miles at 65 MPH. That's about on par with 2016 Nissan Leaf's 30kWh battery, but using 19kWh battery. 55 MPH yields 130 miles, similar to what current SparkEV would get at 24 MPH. Not bad, but drag coefficient of 0.15 would take significant work.

Next, let's see drag of 0.22. While this is still lower than most (all?) production cars, it may be more feasible than 0.15.

At 65 MPH, it's only 87 miles compared to 66 miles with current SparkEV. While that's an improvement, it's nothing to get excited about. I'm not too hopeful for 0.24, something that could be if SparkEV had shape of smaller version of Tesla S.

At 65 MPH, it's only 82 miles compared to 66 miles with current SparkEV. So much for my theory that only aerodynamics is needed for significantly longer range. 55 MPH range is 101 miles. Oh well, at least it can break 100 miles freeway range by looking like a miniature Tesla S.

Still, gaining 20% range with bit of sheet metal work isn't bad. This means similar reduction in drag area (coefficient * frontal area) compared to Bolt could reduce battery size while retaining the 200 miles range. At least there's some hope for Tesla to use smaller battery with 200 miles range EV, that's good.

Edit Feb. 1, 2016

I shrugged off discrepancy between theoretical 158 miles range at 25 MPH and actual 140 miles in experiment by hand waving that efficiency could be different. Now I have new data. I used 500 watts as a guess, but "bicycleguy" from SparkEV forums managed to extract more data using Arduino and CAN bus.

He shows 372.32 Volts total and 3.33 Amps when "on". That would be 1240 Watts, far more than 500 Watts that I guessed. At 55 MPH power of 11 kW, 1240-500 = 740W represents 7%. That's not much off, especially considering that static power doesn't even show on power display.

For lower speeds, however, it would be significant. Using 1240 W as static power at 25 MPH, the range would be

2690W + (1240W  - 500W) = 3430 W
17 kWh / 3.43kW = 4.96 hours, round up to 5 hours
25 MPH * 5 = 125 miles

125 miles for 17 kWh usable battery on 2015 SparkEV is closer to what I estimated based on 19 kWh usable battery capacity on 2014 model.

140 miles * 17 / 19 = 125.3 miles

So maybe the issue at 25 MPH range was due more to static power being different than electrical efficiency at low power levels.

For higher speed (power), static power would be less of an issue, because 0.75kW would be even smaller percentage. But motor efficiency could be different. Unfortunately, I don't have experimental data for high speed to see who far off I might be at 90 MPH, including decreased electrical efficiency. Oh well, maybe someone in Germany could import SparkEV and test it on Autobahn to see how close the theoretical values are.

Below is the new table using 1240 W as static power instead of 500 W.^2&FuelWh=33557&IceEfficiency=.9&DrivetrainEfficiency=.95&ParasiticOverhead=1240&rho=1.225&FromToStep=5-200-5

It's only 78 miles range at 55 MPH, which is even worse in not matching experimental data of 90+ miles at 55 MPH. Oh well, the parameters are still off, but until I get better tools to measure, this is it.

Edit Feb. 9, 2016

I normally leave 1 or 2 bars remaining before disconnecting the charger so I can regen as I'm going down the hill. Recently, I made a mistake and fully charged the car. The range showed 92 miles at Guess O Meter (GOM)!

Charging was after long drive home that was 3.8 mi/kWh. If we assume GOM bases miles on latest drive pattern, 92 miles after 3.8 miles/kWh would be usable battery capacity of 24 kWh. Obviously, this is wrong. Using 5.1 mi/kWh, battery would be 18 kWh. So maybe SparkEV uses 18 kWh out of 19 kWh? I don't know, maybe, maybe not. But 82 miles EPA could be said to be conservative estimate.

Edit Feb.23, 2016

There was a test done on 2014 SparkEV by driving in a big loop in San Diego freeway by Tony Williams (is he the same guy who owns It was found to have 97.8 miles range (92.8 driven + 5 miles remaining) when driven at 62 MPH (100 km/hr) with 5 mi/kWh average consumption.

That would make the usable battery capacity for 2014 SparkEV to be

97.8 mi / 5 mi/kWh = 19.56 kWh
19.56 kWh / 21.4 kWh = 91.4% usable

This is different than 24 MPH test performed by digitaltrends (see above) where the range was 140 miles and 7.3 mi/kWh (19.19 kWh, 89.6% usable). What this points to is that there could be substantial (under 2% is substantial?) difference in range and expected battery capacity. But it's only two samples, so the actual variability is unknown.

Tony also did a similar test using 2015 SparkEV, and found the range to be less, though still much longer than EPA figure. He wrote "shhhh", so you have to search for it yourself if you want to know the actual value. It's actually less than my 55 MPH test (85 miles with 9 miles remaining = 94 miles)

My 2015 SparkEV was getting "roughly" 5 mi/kWh when driven at 55 MPH, though I did not record the number after the trip was over. Due to different gearing, it's possible that 2015 SparkEV is bit less efficient at highway speed than 2014 model (higher motor RPM). In addition, 2015 has 18.4 kWh (some say 18.3 kWh) battery instead of 21.4 kWh of 2014 model.

This COULD make the range on 2015 SparkEV to be less than 2014 model WHEN BOTH ARE NEW. I have to stress "COULD" and "NEW", because the batteries are made by different vendors, LG for 2015 model, and A123 for 2014 model. The way different battery chemistries perform as well as aging would make the comparison difficult today. Suffice it to say, using the low figure of 2015 range is a good conservative estimate; if the range is exceeded, it'd be a pleasant surprise rather than the other way around.

There was also some speculation that 2015 SparkEV uses far more percentage of battery than 2014 model. Some speculate as much as 100%. The range of 92 miles from my recent 100% charging session is consistent with this speculation (18 kWh / 18.4 kWh = 98%). However, going by GOM (guess-O-meter) is not entirely accurate.

Below is a summary table of range in miles for various "simulation" models. First column is using 17 kWh and low rolling resistance tires, the first table I have above (Crr=0.01, 90% efficient, 500W static power). Second column is the same with Crr=0.015 and 80% efficiency (second table from above). Third column is the same as first column with 1240W as static power. Fourth column is the same as first column using 18.4 kWh as usable battery capacity. Fifth column is the same as third column (1240W static power) using 18.4 kWh as usable battery capacity.

Green highlights the closest to data I obtained using 55MPH. I could actually go for 4 more miles, so even this is a conservative estimate WITH NEW BATTERY.

Last columns are average and standard deviation. After all, central limit theorem says it (estimates) will all turn Gaussian eventually, I just skip the middlemen and use only 5 samples (it's a math joke). Because static power and other "issues" would play a bigger role at lower speeds, one should expect large variability at low speeds; turn off your lights and the radio to maximize efficiency at low speeds.

Some ask what the worst case range might be. With windows open, AC, heat, stereo, all of them at full blast, worst case is hard to define. Heat could be substantial in very cold weather (4kW all the time = 20% cut in range). One could have inefficient winter tires + heat + open the window for maximum energy waste. The battery could also have been abused so the capacity is far less. One could be stuck in dead-stop traffic for hours using static power (radio + heat/AC) without actually moving. Without knowing the parameters, it's impossible to say what the worst case range might be. Well, I guess we know: worst case is 0 miles range.

More reasonable case is to go by average figure as relatively safe estimate when operating on flat road with windows closed and no heat / AC. With a new battery, windows down and even little bit of AC or heater use would be in range. However, always leave few miles (I use 10 miles) as a buffer to be able to get to a charger in case the intended charger is out of order. As the EV gets older, it will have degraded battery, so the range should be derated appropriately.

And, of course, a pretty little plot of the data table, too.

Sunday, January 17, 2016

Mass market EV, hoping for Tesla

Previously, I griped about shortcomings of Chevy Bolt.

Chevy still has time to make it better. One would be to make the power 250 HP or more. This may be relatively easy as the 250 HP would only be used for brief burst in acceleration, not sustained.

The other is to make DCFC chargers and help expand the network. Although Chevy stated they won't do anything unless it benefits all their customers, which I read to mean gas cars, they can still change their mind. I mean, Bolt is capable of 150kW charging (3X larger battery than SparkEV), don't they want to test it? Then the test fixture can be made as commercial charger and sold or leased. Isn't there any engineering curiosity, like the guy who made world's fastest lighting BBQ?

Chevy chose to have large battery for range. At 60kWh, it would cost $12,000 (+ labor) to replace it if the pack costs $200/kWh (cell is supposed to be $145/kWh today). Even at $100/kWh, that works out to over $6000+labor when the battery dies after 10+ years. People aren't likely to spend that much money to repair an old car, especially one that performs poorer than comparable gas cars, such as Subaru WRX that comes with AWD and has more power. On top of that, Bolt takes close to an hour to get 80% (160 miles) range. Bolt is pretty much a disposable car.

Model killing Bolt

Then there's another coming: Tesla Model3. While 0-60 performance kicking butt of every car in its price range would be nice, there are two other important metric: range and DCFC time.

What's needed is smaller battery that achieves same range as Bolt and higher power charging. Tesla already has higher power charging: 120kW supercharger network. Assuming no taper to 80% like SparkEV, 15 minutes of charge would be 30 kWh. That needs to have range of 160 miles (80%). Then the total battery capacity would be 37.5 kWh, or round up to 40 kWh (or bit more for margin). 

At $200/kWh pack price, Model3 could be $4000 cheaper than Bolt. After 10+ years when battery prices have come down to $100/kWh, it would be $2000 cheaper. While $4000+labor isn't chump change, it is more palatable than $6000+labor for Bolt, especially if Tesla charges in 15 minutes.

The range on EV is primarily the freeway range. I will cover EV range in more detail in later post, but EV is fairly simple to characterize in that faster you go, the lower the range. What's needed is 160 miles at 65 MPH using 30 kWh (or 200 miles using 37.5 kWh), or 160/30 = 5.33 mi/kWh from battery to wheels.

Is it possible? Yes, of course! SparkEV does between 5 mi/kWh and 5.5 mi/kWh at 55 MPH with its enormous height and awful drag coefficient (0.326 vs Prius 0.28). If Tesla can keep the drag down, it can get away with smaller battery and achieve 15 minutes for 160 miles with their existing Supercharger network. Exact drag also depends on the frontal area, but if Tesla can achieve under 0.2 drag coefficient (EV1 was 0.19), it's probably enough.

On top of that, smaller battery would be lighter. Bolt battery is 960lb for 60kWh, and assuming same energy weight density, 40 kWh would be 320lb lighter at 640lb. That will reduce rolling resistance, further help in range.

Lighter battery would also help in acceleration. Tesla's old 40kWh Model S had 235 HP motor. Combined with lighter than Bolt by about 320lb (3200 lb) that would put it in league of comparable cost gas cars in lb/hp (13.6 lb/hp, better than Fiesta ST). But for 0-60 time, it should be far quicker than gas cars, probably under 6 seconds, maybe even reaching 5 seconds.

EV that does 0-60 close to 5 seconds, 15 minutes to charge 160 miles range, cost about $26K (or $24K in CA), extremely efficient aerodynamics (ie, less noise), now THAT is a kick ass mass market EV I'd be proud to own. Come on Tesla! Let's do this!

Edit Jan. 19, 2016

It seems some have doubts as to what I'm saying. Firstly, unless there's a revolution in battery technology (ie, not Lithium), price is expected to be about $100/kWh. It's also true that few people spend several thousand dollar upfront to fix an old car, especially poor people who tend to drive older cars. Then they'll continue to drive gas guzzling and high pollution cars. In case of pollution, we're not just talking about CO2, but immediately harmful stuff like sulfur oxides, CO, HC, NOx.

The aerodynamics I propose here is not a new idea. From Wikipedia, we can see several cars that have very low drag coefficient.

Limited cars like EV1 has 0.19 and VW XL1 of 2014 has 0.186. While some look comical, Prius has 0.25 (0.24 for 4th gen) while far better looking Tesla Model S has 0.24. Better aerodynamics doesn't have to mean weird.

By far the most impressive is Schlorwagen from 1939 that had drag coefficient of 0.15. If SparkEV has such drag coefficient while retaining current specs (frontal area, weight, battery, etc), it would get about 180 miles range, and charge 144 miles in 20 minutes using 50 kW charger (range using EPA figures) (WRONG! While there will be improvement, I ignored rolling resistance. See EV range blog post in the future for better data). This is only with sheet-metal work, nothing to do with battery.

From the looks of it, it's not conventional looking by the standard of its day. But it's something sort of, kind of looks like what could appear today or in near future. While conventional gas engine did not allow for much flexibility, battery technology can allow far more flexibility in shaping car's body for aerodynamics. For example, there is no poisonous gas coming from the engine that you need to seal off completely from passenger compartment.

When it comes to Chevy type of battery, they are cube blocks. But Tesla uses thousands of 18650 batteries that are typical of laptops. Arranging them in odd shape to have a body shape that minimize drag is far easier. Of course, this assumes Tesla will do such simple minded optimization. They could come up with entirely new way to do things.

But one thing that I hope Tesla doesn't do is brute force: stick ever larger large battery in EV approach. In short term, that'll cost more, weigh more, making it uncompetitive to comparable gas cars. In long term, that'll add to more waste at junk yard and not as many poorer people driving old, used EV, instead driving really hazardous polluting old gas guzzlers.

Edit Jan. 29, 2016

After doing "SparkEV range" post, there are few interesting findings using ecomodder web site.
  1. SparkEV EPA range roughly corresponds 55 MPH range.
  2. SparkEV EPA highway MPGe is roughly 65 MPH MPG.
  3. SparkEV uses 90% of battery capacity.
First point is quite important. I wanted 65 MPH for range, but the EPA seem to use 55 MPH for SparkEV. That's much easier than 65 MPH. Power is proportional to speed cubed. It's also true that Tesla S has 0.24 drag coefficient as tested by third party.

Tesla S60 model

I know SparkEV parameters, and actual experimental data (that I conducted), but I don't have first hand knowledge of Tesla with respect to power vs speed. Still, we can use ecomodder web site using known data to see what turns up. I start with SparkEV parameters, and change the weight to 4323 lb (Wikipedia S60), Cd to 0.24, frontal area to 25.8 (greencarreports).

Knowing that 65 MPH returns roughly the highway MPGe with SparkEV, we can tweak Tesla S parameters until 65 MPH is 97 MPG. Weight and drag and area are fixed to S60 specific data. I use 75% for motor and 90% for drive train and 1000 W for parasitic overhead (for giant 17 inch display?). Rest are kept the same. This results in 96.7 MPG at 65 MPH.^2&FuelWh=33557&IceEfficiency=.75&DrivetrainEfficiency=.9&ParasiticOverhead=1000&rho=1.225&FromToStep=5-200-5

Greencarreports states Tesla S would use 14 HP at 70 MPH, but the table shows that's only to overcome aerodynamics. Since the article was with respect to drag, I think the data I have is correct.

Guess for Model 3

Using the data from Model S, we reduce the weight to 3200 lb (320 lb lighter than Bolt by using 40 kWh battery instead of 60 kWh 960 lb battery). There's some speculation that Model 3 will be 80% the size of S. Given that S is pretty wide, I guesstimate about 90% width (frontal area) as 23.5 sq ft.

The number we are looking for is power at 55 MPH, the number that matches EPA range for SparkEV, and we'll use that number to validate if 40 kWh battery is big enough to achieve 200 miles range.^2&FuelWh=33557&IceEfficiency=.75&DrivetrainEfficiency=.9&ParasiticOverhead=1000&rho=1.225&FromToStep=5-200-5

65 MPH shows 113 MPG, even better than SparkEV highway MPGe (aka, efficiency). 55 MPH shows 9.3 kW. That's 15% better than SparkEV! Let's just make it 9.6 kW, what the heck. Why 9.6? If you have to ask, you won't like the answer!

Now let's see if 40 kWh will be enough to get 200 miles range. Recall that I wanted 30 kWh for 160 miles range (80% of 200 miles) so it can be charged in 15 minutes using 120 kW supercharger without taper. 3 hours at 55 MPH is 165 miles, close enough to 160 miles. Then the energy needed would be

9.6 kW * 3 hours = 29 kWh (oooohhh!)

This meets my requirement with margin to spare. Energy needed for 200 miles range would be

29 kWh / 165 miles * 200 miles = 35.15 kWh (aaahhh!!)

From various experiments, SparkEV is using 90% of battery capacity. From some forum posts, Leaf also uses 90% (22 kWh out of 24 kWh battery). Forum posts? Yeah, it could be garbage, but it sounds plausible from other users' findings as well. Then the battery should be

35.15 kWh / 0.9 = 39 kWh (WOW!!! I'm a genius!)

In effect, what this suggests is that Tesla could be building miniature Model S using 40 kWh battery and calling it mass market EV at lower cost than Bolt. What I wrote above could be a reality with very little design effort from Tesla. That's great news! Where do I buy one?

Keeping up with Teslas

Yeah, only if life is that simple. Tesla may not use 90% of battery capacity like SparkEV and Leaf. In fact, some forum posts say it could be as low as 70%. Let's check that with known numbers. SparkEV has EPA range of 82 miles. S60 has 3 times bigger battery. They have roughly similar power requirement at 55 MPH. Then the range for S60 should be 3 times that of SparkEV at 248 miles. Clearly, that isn't the case as EPA rates S60 at 208 miles.

But let's go the other way. S60 is 11 kW at 55 MPH with 60 kWh battery. To use all 60 kWh, the range would be

55 MPH * 60 kWh / 11 kW = 300 miles

70% of 300 miles is 210 miles. It seems Tesla is indeed using only 70% of full battery capacity. Let's see where it takes us with our Model 3 guess if 70% is used instead of 90%.

35.15 kWh / 0.7 = 50 kWh (ooops!!!!)

It's better than 60 kWh, but 50 kWh is still too high. Of course, most of these values are guesses. Tesla probably can make 40 kWh EV with 200 miles range as mini Model S, but the reliability (ie, range degradation) may not be up to their standard. But if mass market means bit more range degradation, they can relax their standard a bit. One might say "keeping up with Teslas, but not the high end"

Perhaps they can offer various battery options like they do with Model S. Then using 40 kWh battery while keeping 70% battery utilization would result in range of

40 kWh * 0.7 = 28 kWh
55 MPH / 9.6 kW *28 kWh = 160 miles

While it's not quite 200 miles range, 160 miles range is probably good enough for more than 2 hours at 65 MPH.

But what I'm after is 80% to be able to charge at full 120kW power without taper. 80% of 160 miles would be 128 miles. 128 miles is good for about 2 hours of driving in freeway, though it'll probably be 60 MPH. Combine that with less than 15 minutes to charge, that would still make for very compelling mass market EV, especially if the price is lower by thousands of dollars compared to 60 kWh Bolt.

But as I wrote above, I hope they don't just stick with large battery for range whatever they do. Brute force is not an elegant solution to engineering problems.

Edit Feb. 25, 2016

It seems ecomodder web site only uses motor efficiency for MPG figure, not the power in kW. Then the above analysis using power is wrong (oops!) One should use MPG column. Using 134.4 MPGe at 55 MPH,

134.4 MPG / 33.557 kWh/gal = 4.0 mi/kWh
4 mi/kWh * 60 kWh * 0.8 = 192 miles (60 * 0.8 / 120 = 0.4 hours, 24 minutes for 80% of 60 kWh)
4 mi/kWh * 40 kWh * 0.8 = 128 miles (40 * 0.8 / 120 = 0.27 hours, 16 minutes for 80% of 40 kWh)

Those would be roughly EPA's rated range. More usable is 65 MPH range. Using 113 MPGe at 65 MPH,

113 MPG / 33.557 kWh/gal = 3.37 mi/kWh
3.37 mi/kWh * 60 kWh * 0.8 = 162 miles (24 minutes charging)
3.37 mi/kWh * 40 kWh * 0.8 = 108 miles (16 minutes charging)

Huge oops!

However, that was assuming motor efficiency of 75%, something they may be able to improve upon for lower performance than Model S. At 90% efficiency, 65 MPH shows 136 MPG. Then 40 kWh range would be similar to 55 MPH case above. 128 miles using 80% of battery at 65 MPH is almost 2 hours of driving. That's quite satisfactory for almost all cases, especially if it allows 16 minutes to charge and cheaper by thousands of dollars than Bolt.

Thursday, January 14, 2016

Mass market EV, To Bolt or not to Bolt

Chevy announced Bolt to the public long ago, but the details have been lacking until recently. At 2016 CES, they announced that the battery will be 60 kWh, giving it a range of 200 miles. At NAIAS (North America International Auto Show), they announced further details. Curiously, Chevy's Bolt web site doesn't list performance figures, but only that it's 200 miles range EV and 9 hours to charge, and doesn't even mention fast charge using CCS.

Did Chevy forget that it's a car company, and not a electric-thing-a-ma-jig company? While SparkEV prominently lists horsepower and torque, Bolt power number is buried deep while they drone on about connectivity, something that even $10 cell phones have nowadays. So deep, in fact, that power is not even mentioned on its main website. While Nissan Turtle (oops, I mean Leaf) or Mitsubishi Snail (I mean iMiev, one of the slowest cars on the road) can get away with slow as molasses EV by claiming that they get the best range in their class, a car company that makes Corvette and SparkEV shouldn't be ashamed / hide its car's performance.

Digging further, I found the spec here.

Some key figures:

200 horsepower, 266 ft-lb of torque
60 kWh battery
90 miles charging in 30 minutes using CCS
50 miles charging in 2 hours (25 miles per hour, 7.2kW L2)
3580 lb (960 lb battery)
0-60 under 7 seconds (how low? we don't know yet)
0-30 in 2.9 seconds
$30,000 after subsidy (probably $37,500 MSRP)

Great EV performance

One obvious performance figure worse than SparkEV is the torque. While SparkEV was 400 ft-lb in 2014 and 327 ft-lb in 2015, key figures prominently displayed at Chevy's SparkEV web site, 266 ft-lb is much less than SparkEV. But the power is more than SparkEV, so that's good, right?

3000lb / 130HP = 23 lb/HP (SparkEV)
3600lb / 200HP = 18 lb/HP (Bolt)

As far as EV's go, Bolt has far better weight to power ratio than anything in its price range.

0-60 time isn't known other than "under 7 seconds". Assuming 6.5 sec and 6.9 sec for 0-60, using my "range-performance-cost" metric from my previous EV ranking post,

200 miles / 6.5 sec / 30 * 1000  = 1026
200 miles / 6.9 sec / 30 * 1000  = 966

Those  scores are better than all EV, including Tesla. If you're in the market for an EV and only EV, and you have $30K to spare, Bolt is the clear choice, at least for now; let's see how Tesla Model 3 does later in the year. It only costs $4K more than Leaf with 110 miles range / 0-60 in ~10 sec. In fact, it may perform even better than BMW i3 while costing less and 2.5 times the range.

Bolt is a winner? Not so fast.


I got excited about SparkEV and people get excited about Tesla P90DL, because they are better performing than all cars in their price range, not just EV. I can't get excited about cars that perform poorer than comparably priced gas cars. For example, Leaf with its 0-60 in 10 sec was quickest EV in its price range when it first came out (against cars like Zap!), but it was one of the slowest cars in its price range. That's not something to get excited about. It just reinforces the stereotype that EV is over priced, under performing glorified golf cart.

At first glance, Bolt suffers the same as Leaf. Compared to gas cars of about $30K, Bolt seem to be highly lacking. Below table shows how comparably priced gas cars perform from car and driver web site. As usual in my blog post, yellow (jersey like in bicycle race) highlights the best.

As you can see, Bolt drops to bottom of the pack of comparable cost cars when it comes to weight to power ratio. Well, that sucks. It would seem Bolt is a dud. But who cares if a car makes 1 lb/hp? What matters is 0-30 and 0-60 time with respect to price, because that's what's most used in everyday driving: traffic light show off and merging in freeway. Like EPA's MPGe, lb/hp has little meaning when it comes to real world performance.

Slow 0-30 times

Often, EV folks crow about quick 0-30 mph times of EV due to "instant torque". Here, the numbers are difficult to find for gas cars, but Bolt spec shows 2.9 seconds. Well, that SUCKS! SparkEV does it in about 3 seconds, and it's $12K cheaper. Far more importantly, gas cars of comparable cost perform better.

VW GTI is listed as 2.2 seconds ($29.5K). Ford Focus ST is listed at 2.4 seconds ($31K). As far as "drag race" at stop light to stop light against comparable cost cars, Bolt loses by wide margin.

0-60 time-price product

Better metric for comparison is 0-60 with pricing as consideration. However, Chevy doesn't list the time for 0-60, only that it'll be under 7 seconds. Then we're left to guess. I guesstimate 6.75 seconds. Though SparkEV is not in competition, it's highlighted in green.

Once again, Bolt is at the bottom. What's embarrassing is Bolt performs poorer than all gas cars in 0-60, including Fiesta ST that cost $7500 less! Bolt would be a loser if 0-60 is more than 6 seconds (only slower than GTI, WRX that cost $2500 less), though 5 seconds would barely make it a winner.

As before in EV ranking, I square the 0-60 time to give advantage to higher cost quicker cars. Even then, Bolt comes in at dead last.

5-60 time-price product

What's strange about car and driver is that they list many different figures for acceleration. For some cars, they use method somewhat like my "slip the clutch" acceleration. Using this method would surely yield best 0-60 times for gas cars. Indeed, such method could allow stock Corvette to beat Tesla P90DL in 0-60 time as I describe in my previous blog post. Neener neener to those who thought gas cars can't have peak torque from 0 MPH!

But that's not what people would do in terms of everyday driving in merging to freeway. They'd engage the clutch as soon as possible to minimize clutch wear and allow the engine power at appropriate RPM to accelerate. Such metric seem to be what car and driver calls "5-60 rolling start". Because Bolt would (should?) have close to max torque available at start, starting at 5 mph would yield lower time than 0-60, so I guesstimate 6.5 seconds for this comparison.

Car and driver also list many different prices: main price in bold, base price, and tested price. Tested price is with many options that may or may not have to do with acceleration. But it's impossible to separate them out, so I use tested price for comparison. This will give advantage to Bolt.

Well, well! Bolt isn't so bad after all! In fact, acceleration would be right in the middle of the pack between WRX and Ford Focus ST, though WRX has all wheel drive. When 5-60 time is squared, Bolt comes in between WRX and Fiesta ST, though Fiesta ST is lot cheaper. Oddly, Subaru WRX STi is slower than WRX while it has more power. Maybe the gearing isn't optimized for 5-60 runs, who knows?

An interesting side note is that SparkEV at $15K in CA ($26K - 7.5K(fed) - 2.5K (CA) - 1K( Chevy has $1K discount going on)) would perform better than Fiesta ST that cost $10K more, and close to Focus ST that's double the cost. Even though the time used for SparkEV is 0-60, and not lowered like with Bolt, SparkEV comes out at top even after squaring the time.

Performance assessment

I'm guessing Bolt's 0-60 times, and it's hard to know how much cost was involved in extras not related to performance for comparably priced gas cars, so 5-60 is probably the best case for Bolt. It's not the best of the pack, but not the worst. When it comes to bragging rights for 0-30 and 0-60, Bolt would probably lose when gas cars employ "ride the clutch" acceleration method. But when it comes to everyday driving, Bolt would be in the middle of the pack of comparable cost gas cars.

Or is it? Remove Ford from the list, and Bolt guesstimate again drops to the bottom of the pack in terms of absolute 5-60 time. What's saving it from being the bottom with respect to 5-60 price product would be the federal tax credit. Since most people will take the tax credit, Bolt is still not too bad, though not at the top of the game like SparkEV.

As a successor to SparkEV, that's an embarrassment. SparkEV is quicker than all gas cars of comparable cost. It's even quicker than cars that cost $10K more, and almost as quick as gas cars that cost twice as much, Fiesta ST and Focus ST, respectively. I guess one reason might be that Ford sucks. But the real reason would be that Chevy engineers did one hell of a job with SparkEV, but only so-so job with Bolt.

Slow charging

As I mentioned above, Chevy's main Bolt web site doesn't even list fast charging information. WTF? Unlike gas cars, people are unaware that they can "fuel" EV using fast charge and drive many times the battery range in a day. Highlighting 9 hours charge time as if that's something to be proud of is to say "don't buy Bolt; it sucks!"

From other sources, we can glean few things from this. 9 hours for 60 kWh battery is 6.66 kW. Spec shows 7.2kW. But that could be a problem for some (many?) people. At 7200W / 240V = 30A. This is significant current that may require special wiring at home. SparkEV's 16A was far easier on house wiring as many (most? all?) wall sockets wiring can accommodate the current. I suspect some (many?) will be in for a surprise when they find out that their home needs wiring upgrade or they have to use 3.3kW EVSE and take close to 20 hours to charge.

Far more important and far, far worse is DCFC speed. At 90 miles per 30 minutes, that seems to be 50kW charger. To get 80% of 200 miles (160 miles) would need

160 / 90 * 30 = 53 minutes!

In contrast, SparkEV would reach 80% in 20 minutes. If people only charge to X miles just to get to their destination, Bolt is fine. But human psychology is such that they look for X%, not X miles. Waiting almost an hour at DCFC is pretty sad. Chevy went from being the quickest charging EV in the world with SparkEV to slowest charging EV in the world with Bolt.

I only discuss DCFC as I consider non-DCFC as toys, not real vehicles.

Of course, it doesn't have to be this way. CCS is rated to 170kW. At 3 times the battery of SparkEV, 150kW charger would put the Bolt back in the game as one of the quickest, if not the quickest charging EV in the world. I'm pretty sure Chevy has the engineering talent to pull it off. But alas, Chevy doesn't seem to care about this very important aspect of EV, which is fast charging.

So Bolt will be the slowest charging EV in the world. Sometimes, I feel like taking over Chevy and slap some sense into them.

Would I buy Bolt?

In a word, no. While Bolt isn't bad in 0-60, it's not great. After SparkEV, I've come to expect greatness from EV, not just merely "ok". Settling for Bolt just because it's an EV when better gas cars (performance and/or space, towing, convenience) at comparable or lower prices are available doesn't make sense to me. It's like, well, buying a Nissan Leaf: EV turtle.

Even worse, $30K is significant amount of money. I can be convinced to drive a new car, EV or otherwise, for $15K (or even $18K), but definitely not for $30K, especially a compact car like Bolt. At $12K more than SparkEV, that's over 10 years of eating at $1/meal ($3/day), an experiment I successfully tried for months while ago, and some made documentary about such endeavor.

If Bolt is a van, truck, or SUV that can carry stuff, it might make for a better case at $30K and so-so performance. In that regard, I wish Toyota continued to improve on Rav4EV; at 120 miles range with 0-60 in 7.2 seconds and $42K, I wish they could improve on it to bring the price down to $30K and 150 miles range; will discuss why 150 miles later.

Compounding the matter is Chevy's unwillingness to participate in DCFC infrastructure. They don't have to give out free charging (THEY SHOULD NOT GIVE OUT FREE CHARGING), but they could install them at all their dealers and charge nominal fee to recoup the cost. If they do, other EV drivers would stop by their dealer and check out Chevy cars while charging. Foot traffic at the dealer would be more than enough justification to install high power DCFC at the dealers.

Alas, this is not to be, and I don't want to support a company that sells EV without adequate way to use / charge it, especially at $30K.

What mass market EV would I buy?

Before this is answered, I have to answer what new gas car I'd buy. That's Hyundai Elantra. It's price is under $20K, has decent styling, close to 40 MPG, can tow 1500 lb which makes easy home depot runs for plywood using $250 harbor freight trailer.

First and foremost would be pricing under $20K. At $22.5K, that's in Prius ballpark. While that's tad high for my taste, I can squeeze out bit more for better car than Elantra.

Second has to be performance better than all gas cars in its price range. As shown above, Fiesta ST does in 6.7 seconds 0-60, so 6.5 seconds might be fine (Bolt may actually do this), though under 6 seconds would erase all doubt. Therefore, 0-60 must be under 6 seconds at $22.5K, preferably under 5 seconds.

Third is fast charging. While home charging overnight for 12 hours is fine, DCFC must be 80% in 20 minutes or less. In this regard, it's not just EV, but Chevy must actively participate in charging infrastructure (again, DO NOT GIVE OUT FREE CHARGING!) to allow 20 minutes for 80%.

Fourth, the range doesn't have to be 200 miles. Without DCFC, even 2000 miles range would not be enough. But with DCFC, it should be at least 2 hours at 65 MPH freeway with 15 minutes of charging.

65 MPH * 2 H = 130 miles

But one must have some margin. Let's say 20 miles for 150 miles range, though 10 miles would be ok, too. Assuming 3.5 mi/kWh at 65 MPH including heat/AC, that works out to

150 miles / 3.5 mi/kWh = 43 kWh (round up to 50 kWh)

To charge 80% of 50 kWh in 15 minutes,

50 * 0.8 = 40 kWh
40 kWh / 0.25 H = 160 kW

A 50 kWh battery charging at 160kW is rate of 3.2C. Whether current EV battery can do this is unknown. From few articles I've read, even 10C charging is possible for some chemistry. But we know SparkEV can do 48kW using 19 kWh battery, a charging rate of 2.5C (48/19). If we assume 2.5C that is currently possible with SparkEV, time to charge 80% would take

50kWh * 2.5C = 125kW
50kWh * 0.8 / 125kW * 60 min/hr = 19.2 minutes

125kW is about what Tesla supercharger can do today. Basically, the point is that practical mass market EV charging can be done that isn't much more of a hassle than gas cars, but not with today's CCS from eVgo. Chevy must actively develop and deploy and/or help deploy such charging network.

Fifth is 1500 lb towing capacity. Light towing makes the car so much more versatile. If I get another car, it will have to have towing capability. Another consideration for EV might be range extender trailer, either as extra battery or gas engine generator. Unfortunately, towing ability rules out all EV except for Tesla Model X at the moment.

So how does Bolt stack up from my requirements?
1. Pricing, No,
2. Performance, maybe, though probably lacking.
3. DCFC speed, No, especially with Chevy's lack of interest in participating.
4. Range, Yes.
5. Towing, No.

One out of five? Not likely; I'd rather get Elantra.

Mass market potential

If above criteria are met, I suspect it'll meet the needs / expectations of most people. After all, EV that performs better than all cars in its price range AND it can charge almost like gas cars on longer trips AND all the benefits of EV, such as home charging and quiet, smooth operation is hard to pass.

Some places give large subsidy for EV. US is one, and CA gives additional. Recently, Germany announced 2 billion euro to encourage EV. Big slice of that pie could go to the compelling mass market EV maker, and those who participate in charging network.

There's lots of money to be made for true mass market EV. Unfortunately, I don't think Bolt is it.

How about SparkEV? It could very well be the mass market EV with right pricing and options and marketing. In foreign countries where the roads are narrow, small car is actually of advantage. Combined with exciting performance for price, it holds lots of appeal with proper marketing. Going through the list of criteria above,

1. Sub $20K Pricing, Yes in US, probably in many other countries as well.
2. Performance, Yes. Chevy need to advertise this aspect with gusto.
3. DCFC speed, Yes, SparkEV is quickest charging EV in the world.
4. Range, No. However, with enough DCFC and marketing, it's not as big a deal.
5. Towing, No. But next gen can easily allow for this.

3 out of 5 is already met today, and towing is easily resolved. In fact, range extender trailer could solve the range issue as well. All Chevy need to do is market it to take advantage of the huge potential for EV in places like Germany. It's far easier to convince people to drive kick-ass car that happen to be an EV that cost $18K ($15K in CA) than $30K that's ho-hum. I mean, Chevy already did all the engineering work for SparkEV, why abandon it? All they need is to install DCFC at all their dealers (and price it to recoup cost), and run some commercials. Who knows? Maybe people will drop by to buy Bolt and Silverado as well.