Range Confidence: Charge Fast, Drive Far, with your Electric Car

By David Herron
Electric car drivers want autonomy, the freedom to drive anywhere, anytime. Over the last 100 years or so of gasoline powered transportation we grew to believe that gasoline is the only means for that freedom. As we collectively move to electric cars, we bring with us a belief that cars can drive anywhere, and therefore electric cars should do the same. Indeed, they can, and let's discuss how electric cars can have as much autonomy as gasoline.

The American road system is designed around the promise of the open road, and driving whenever and wherever we want.

That ideal may be lost on us during rush hour with jammed highways that have turned into parking lots. But, this is the idea car companies have sold to us over the years. That ideal is what we demand our governments build for us.

While going over the steps to learn Range Confidence (Learning Range Confidence), we asked you to think about your Real Needs. If you're like most, your real need is the 40 miles or so a day going to work and back, and some occasional longer trips. That freedom to go anywhere anytime is interesting, but is that your real need?

At the same time we clearly need the flexibility to take trips outside our normal boundaries. We might be at work, the mother-in-law has an emergency illness, and we suddenly need to drive a hundred miles away to take her to a hospital. Can we wait 3 hours for the car to finish charging? Nope. The spouse won't like that, understandably, and it could be a health risk.

While the average person, on an average day, drives less than 40 miles a day, we all will face sudden needs to drive a long distance.

The attributes of Autonomy:

  • Enough driving range for normal daily driving needs
  • Suitable recharging capability at work and at home for normal daily driving needs
  • Total driving range per day to satisfy our normal daily driving needs
  • Fast recharging availability when we need to drive farther
  • Fast enough recharging to sustain longer distance drives when needed

In other words we must understand this:

  • Normal daily driving needs
  • Exceptional driving needs

And we must ensure the car has a large enough battery pack for daily driving needs, and a fast enough charging system to handle exceptional driving needs.

In part electric car autonomy is gained from a large battery pack. But a large battery pack charged at 6 kiloWatts could take a full day for a full recharge. In other words full autonomy comes from a combination of battery pack size and recharging speed.

In Total driving range in electric cars: plug-in hybrid versus fast charging we defined Total Driving Range as the absolute maximum possible driving distance with a given car in optimum refueling circumstances. If you had the perfect driving terrain, with perfectly spaced recharging stations, what's the furthest you could drive per day?

Practical example - rescuing the mother-in-law

Returning to the scenario just named, let's get into the details. You're at work, and the mother-in-law is 100 miles away. Perhaps the spouse is already on his/her way, and you need to join them as quickly as possible. Your car has only 20 miles range remaining range and is on a 6 kiloWatt charging station.

You'll need to gain about 100 miles of range very quickly. You will need 80 miles range to reach the mother-in-law, another 20 miles (or more) for the margin to keep the battery pack from running too low, and another 20 miles (or more) to handle driving needs once you get to the mother-in-law.

At a 6 kiloWatts charging rate the rule of thumb is 20-25 miles range per hour of charging, and therefore you're talking 4+ hours just for charging. On the normal day at the office that would have been enough so the car is fully charged by the end of your work day. But your work day has been interrupted by an emergency.

You can't wait that long. What do you do?

Driving to the mother-in-law will take 1.5 - 2 hours, and your spouse will just have to deal with that as a fact. Your job is to minimize the charging time.

That means using fast charging stations. Depending on the charging power you'll be able to get enough range in an hour or so of charging.

You will need to already know fast charging station locations along the route. That way you can just hop in the car and go. The last thing you want is to be fumbling with maps while trying your darnedest to keep the spouse satisfied with your ability to respond to an emergency situation.

Practical example - escaping a Hurricane

Thanks to climate change, extreme weather is more common. This means we'll more and more frequently face the need to suddenly pack up the car and the family, and flee our nice wonderful coastal city because a Hurricane is about to make landfall and the authorities have issued a mandatory evacuation notice.

The question is, will you be able to drive away from a life-and-death situation where you absolutely must flee right now.

Pondering this, it seems the primary consideration is the distance you must drive to get to safety. It's unlikely you'll be able to rely on any refueling infrastructure of any sort, either gasoline or electric, because you'll be surrounded by hundreds of thousands of people fleeing the same event. You'll be left driving as far as you can, and then possibly unable to find charging or else face a long line at the charging station. Every refueling station, including gasoline, would be swamped with other refugees also desperate to refuel their car.

Much depends on preparations made by the authorities. Will they arrange sufficient emergency fast charging stations? Will there be enough electrical capacity during the emergency? Will there instead be enough trains or busses to carry everyone to safety?

As electric vehicles become mainstream the emergency agencies do need contingency plans to handle emergency electric car refueling.

Actual example of escaping Hurricanes Harvey and Irma, 2017

The 2017 Hurricane season saw at least two back-to-back super-Hurricanes strike the USA. Hurricane Harvey slammed into Houston in late August, causing an immense amount of flooding, damage to oil refining infrastructure, many chemical plants spewing toxic everything into the flood waters, other chemical tanks exploding, and so on. Then a couple weeks later, Hurricane Irma is poised to hit Florida with more energy/strength than Hurricane Andrew in the early 1990's. Earlier in its track, Irma was recorded with wind speed over 185 miles/hr, perhaps the strongest Hurricane ever recorded, and it destroyed most of the habitable structures on several islands.

Officials in Florida have ordered mandatory evacuations ahead of the expected devastation of South Florida. The evacuations mean traffic jams many miles long, and scarce fuel supplies for those unfortunate enough to drive gasoline/diesel-powered vehicles. Going by reports on social media, electric car owners easily found electric car charging.

That is, reports are that Supercharger stations are readily available and it's far easier to get out of Florida with a Tesla than with a gasser vehicle. Lots of gas stations in Florida are either out of gas or there are long 3+ hour waits to fill up. As long as electricity is stable a charging station will work fine, while a gasoline station can easily run out when gasoline demand is high and/or if supply is disrupted. The news is full of reports of panic buying of everything including gasoline.

The only map charging map showing station status -- the ChargePoint map -- indicates the majority of fast charging stations are "green" and therefore available for use.

Another question is whether electricity disruption would render charging stations useless, and therefore make the electric car useful. Reports are that Tesla Supercharger stations in the Houston area stayed in operation after Hurricane Harvey. The ChargePoint map shows all Houston-area charging stations are in operation.

It may be that EV owners of shorter-range electric cars are leaving them at home and driving a gasser to safety instead. There's at least one post from a Nissan Leaf owner describing worry over having left their Leaf at home and wondering whether the car would survive the hurricane. Tesla owners, between a longer driving range and excellent fast charging infrastructure, are justified in feeling confidence to drive their EV far enough to escape the hurricane. A Leaf owner with an 80 mile range and less mature fast charging infrastructure can justifiably worry whether the EV would take them to safety.

Solving the problem of taking a long trip with an electric car

It's understandable to believe that a 4-hour recharge time for electric cars makes them impractical for road trips. Nobody wants to drive a couple hours, charge for four hours, drive for 2, then charge for four. At the same time there are folks who have taken long trips with an electric car doing exactly that.

We just named off a couple emergency scenarios that will be challenging for an electric car driver. The vast majority of us don't face emergencies every day, or even long range trips every day, but we still need the capability to take long range trips. If only so we gain the most benefit from these cars, by using them for as many trips as possible.

We need to challenge the belief that electric cars are only suitable for around-town driving. For electric cars to give the most benefit (both economic and environmental) we need to drive electric for all our driving needs.

Long trips are more feasible in an electric car with more autonomy. Proof? Just look at the Tesla electric car owners gleefully driving coast-coast. While Tesla sells cars with large battery packs, they've also built a charging network designed to support long distance driving.

The combination to look for is:

  • An electric car that's affordable for the regular person
  • Enough range -- 150 miles or more range should be the minimum
  • Enough fast charging infrastructure, not just in towns but between major cities

Range Confidence is Copyright © 2016-17 by David Herron

About the Author(s)

David Herron : David Herron is a writer and software engineer focusing on the wise use of technology. He is especially interested in clean energy technologies like solar power, wind power, and electric cars. David worked for nearly 30 years in Silicon Valley on software ranging from electronic mail systems, to video streaming, to the Java programming language, and has published several books on Node.js programming and electric vehicles.
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