Sunday, May 24, 2015

DCFC (quick charge) and Driving from LA to NY

One of the most practical qualities of EV is quick charge. Without it, EV loses much of its utility. Charging for hours with L2 is only when one goes to work and home. DCFC allows the car to be driven to two or three times the battery range without much pain. Even several hundred miles a day is possible with some pain. Even 1000 miles may be possible with lots of pain. For anyone considering an EV, DCFC is absolutely essential. Even if it's supposed to be an option, take the option. It's more than well worth it. It's essential.

Following thought experiment shows what SparkEV can do. Unless traffic jam is eliminated in CA or my plan for alternative to high speed rail is executed, this is only theoretical.

SparkEV has 85 miles range (95 miles at 55 mph). But one should give some margin of error. To make math simpler, let's assume 65 miles of usable range (1 hour drive at 65 mph); one should be able to find DCFC in 20 miles or at least L2 to get to DCFC. But let's assume DCFC only for this exercise. Let's also assume that DCFC takes 10 minutes out of the way (5 min to get off the road, 5 min to get back on the road after charge) and 20 minutes of charge time to get another 65 miles range for 30 minutes per DCFC session. I actually got from 4 miles to 84 miles in 22 minutes 54 seconds, so this is very conservative assumption. Assuming one starts off with full charge from home,

To go 130 miles, (65 + 65*1) / (1 + (1 + 0.5)*1) = 54 mph average
To go 195 miles, (65 + 65*2) / (1 + (1 + 0.5)*2) = 48.75 mph average
To go 260 miles, (65 + 65*3) / (1 + (1 + 0.5)*3) = 47.27 mph average
To go 1040 miles, (65+ 65*15) / (1 + (1 + 0.5) * 15) = 44.25 mph average

Time to go 1040 miles is the denominator, which is 23.5 hours. One can drive over 1000 miles in a day with 15 DCFC sessions if one starts with full charge! But where in So Cal can one drive at 65 mph for 65 miles, let alone 1040 miles? We can only dream. Or not; stay tuned for SparkEV vs CA high speed rail coming in the future.

To find the average speed to go infinite miles, we use L'Hopital's rule. You do remember L'Hopital from Calculus, don't you? Mr. Escalante would be mad if you don't! "Hey Kimo, you want fries with that?"

65 / (1+0.5) = 43.33 mph average.

Theoretically, it will take under 3 days to go from LA to NY. It's not yet possible as of May 2015, but if all Chevy dealers across America put in public DCFC, it may be closer to reality. Seeing how GM has been the dunce of the class until SparkEV, they should sell fries, too.

Edit: 2016-10-20

I elaborate on 1000 miles a day theory in another blog post here. Scroll down to "1000 miles a day revisited".

To repeat myself from that post, someone drove over 1000 km in one day (16 hours) with SparkEV using multiple DCFC with average speed of 40.6 MPH. 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.

Unfortunately, LA to NY still isn't yet possible as of Oct. 2016 since there aren't enough DCFC along the route. But if it's available (hopefully soon), and average distance of 650 miles a day and 8 hours of sleeping, and assuming the distance is 2800 miles (2776 miles according to Google), it would take 4.3 days.

That's with sleeping 8 hours every night and having 13 charging breaks a day to avoid fatigue. It's probably not far from what typical people would do for such long trip, even with a gas cars. 650 miles is literally 10 hours of driving, something that most people cannot handle in a day.

But let's say you wanted to skip sleeping. At 975 miles a day, it would take 2.9 days (69 hours). The record for the trip on gas car is about 30 hours, so SparkEV would take much longer. But who does that? For most long trips that are sporadic, SparkEV would do just fine.

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