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Close call: Will the Tesla make it to the next charging station?

Globe Drive's Peter Cheney is driving from San Diego, California to Whistler, B.C. in a Tesla Model S, which is powered only by electricity. This is the fourth day of his journey.

The Series:

Facebook: Visit our Facebook page for more videos from Peter Cheney

All charged up: Pumping electricity at the Supercharger station

Day 3: How long before we can leave gas stations behind for good?

Day 2: Tesla takes on the Hollywood Hills with power to spare

Day 1: Electric Tesla on its way from San Diego to B.C.

Introduction: Can our writer make it from San Diego to Whistler in a Tesla?

Peter Cheney

As a newcomer to the world of long-distance electric-car travel, I was playing it safe. By the time I left San Francisco yesterday on the third day of my journey from San Diego to Whistler, I’d charged up the Tesla Model S half a dozen times. And I made sure every one of those was a full charge – it takes a while to get used to the idea of travelling on nothing but a battery, and I wanted all the range I could get.

Marian Cheney

The only problem with this conservative approach is that you spend more time than you need at Supercharger stations. Charging is an exponential process: the first part of the Tesla charge goes fast, but as the battery approaches 80 per cent, the car’s software slows down the power flow.

Experienced Tesla owners don’t usually shoot for a full charge. Many of them connect to the Supercharger for just 10 to 15 minutes, adding enough charge for the next leg of their trip, plus some reserve.

Peter Cheney

So when I charged up for my drive to Mt. Shasta yesterday afternoon, I decided to stop playing it safe. The charge station was in Corning, a small town in the golden flatlands north of San Francisco.

After three days on the road, I was becoming comfortable with Tesla’s powerful navigation and energy-management software, which continuously monitors power usage and predicts your range. I plugged in the car and walked over to Starbucks. Tesla charge stations are usually next to restaurants or outlet malls.

Peter Cheney

I’d spent the first part of the day in San Francisco shooting pictures and video of Tesla on the steep hills. Now it was getting late, and I wanted to make it to Mt. Shasta before darkness fell. It was time for my first partial charge. I got my coffee to go, and unplugged the Model S after just 16 minutes on the Supercharger. The energy display showed 275 kilometres of range. If I waited another 20 minutes, I’d get a full charge, which would give me about 430 kilometres, but Mt. Shasta was only 173 kilometres away.

Range calculation is a complex process. Every car, whether it’s powered by electricity or gas, consumes power at a constantly varying rate. The main variables are weight, aerodynamic drag, grade, and driving habits. A skilled driver can double the fuel economy of a lead-footed hack by minimizing throttle changes and driving at optimum speeds.

Marian Cheney

But the road can change everything. And I was given a brutal reminder of this yesterday.

I’d never driven the stretch of road from Corning to Mt. Shasta, but as I headed north, I realized that there might be some significant elevation change. I watched the Tesla’s range-prediction screen, and noticed that my power consumption trace (an orange line that looks like an EKG) was trending upward. And my predicted range was falling. I asked my wife to Google the elevation of Corning, and the town of Mt. Shasta. The difference between them appeared to be over 3000 feet.

After 65 kilometres on the road, the distance to Mt. Shasta had fallen to 108. But my predicted range had gone down even faster, and my power consumption was rising as the road tilted gently upward. I’d started the trip with 102 kilometres of surplus range. Now it was down less than 70. Five minutes later, the surplus dropped to 62. I lowered the speed to reduce aerodynamic drag (drag increases as the square of velocity, so even small speed reductions can reduce fuel consumption by a significant amount.) Our predicted range inched upward. Making it to Mt. Shasta looked tight, but possible.

Marian Cheney

Marian Cheney

Or was it? I checked the altimeter in my watch (I’m a glider pilot, and I obsess about altitude.) We had climbed about 250 feet since Corning, so there was probably 2700 more feet of altitude to gain. That would cost a lot of energy.

Over the next ten minutes, the predicted range surplus started falling. If we made it to Mt. Shasta at all, it would be on fumes. I felt like a bomber pilot heading back from a long mission, staring at the fuel gauges and praying that the airport would appear before the engines quit.

There were no charging stations ahead. It was Mt. Shasta or bust.

Peter Cheney

When I did the initial planning for my long trip from San Diego to Whistler, I used a spreadsheet to break the journey into segments, calculating the distance between potential stops and determining how much margin we’d have. Travelling in an electric car like the Tesla Model S takes planning – but it’s amazing experience, and you travel for free, since Tesla gives you lifetime charging with the car.

Peter Cheney

If I’d followed my original plan, and topped of the battery at every charge, the drive to Mt. Shasta wouldn’t be a problem. But now my decision to cut the charge short had us in a deteriorating situation. It was decision time – go, or no go? We got off at the next exit and turned south, back to Corning and the Supercharger station.

Peter Cheney

We plugged in the car and found a restaurant. Our aborted start had cost us about 165 kilometres. And since we’d already booked a hotel in Mt. Shasta, we had no choice but to start over again. We arrived here late last night. (I think we had about 120 kms of range to spare, but by this point I was a little punch-drunk from a long day.) Today we head toward Portland, Oregon – with fulI charges at each stop.

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