Road Trip Recharging Strategy - 2013 Tesla Model S Long-Term Road Test
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2013 Tesla Model S Long-Term Road Test

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2013 Tesla Model S: Road Trip Recharging Strategy

January 10, 2014

2013 Tesla Model S

A few commenters were critical of the recharging strategy I employed during my 2,000-mile road trip in our long-term 2013 Tesla Model S. Namely, I'd fill only partway, putting in enough miles to reach the next Supercharger, plus an extra buffer. For this I was chastised as an EV newbie and tut-tutted for not doing complete charges.

The irony here is that those doing complete charges at each Supercharger are revealing themselves as EV newbies. The reason is time. Filling the last 20% doubles the amount of time you're sitting at the Supercharger compared to filling to 80% from empty. Science!

Since my route required recharging at every Supercharger along the way, the most time-efficient strategy is to roll into each Supercharger with a nearly-empty battery, put in enough miles to reach the next one (plus a bit more, just in case), then hit the road. Doing a complete charge at every Supercharger would have been a colossal waste of time, adding hours, not minutes, to an already long trip.

In fact, partial fills in this manner are recommended on Tesla's website:

"Optimal Charging

The fastest way to replenish your Model S is to charge to 80% state of charge, which is more than enough for travel between Supercharger stations. Charging the final 20% takes approximately the same amount of time as the first 80% due to a necessary decrease in charging current to help top-off cells. It's somewhat like turning down a faucet in order to fill a glass of water to the top without spilling."

What's needed is route topography to be taken into account in the Tesla's navigation system. You'd program your route and the system would make a rough estimate of how much additional range will be sucked out by hills along this route. Easy for me to say...

Incidentally, when you're on the fourth recharge of the day and you've eaten all the crummy fast food you can stomach, done plenty of aimless walking around, caught up on emails, your bladder's empty and you're parked in the back of a restaurant parking lot in Grant's Pass (colloquially referred to as "Grant's Ass") in winter, getting back on the road and making some kind of progress toward your destination becomes your mission in life. Stopping every 150 to 200 miles does lose its novelty in a hurry during a trip like this.

Jason Kavanagh, Engineering Editor


Comments

  • greenpony greenpony Posts:

    Um... Where did all the comments go?

  • dgcamero dgcamero Posts:

    Doesn't the Tesla use Google Maps for navigation? Too bad Google has removed all of the nifty extra features such as elevation profiles from Maps when they switched Android's version to be identical to the crippled iOS version. Seems like it would have been an easy addition to Tesla's Maps firmware before the removal of the useful features.

  • fordson1 fordson1 Posts:

    greenpony, I think probably the same person who was responsible for putting a lot of comments that should not be here has now taken away a bunch of comments that should be here.

  • nicad nicad Posts:

    Great that we are getting an unbiased review of someone who is discovering the Pros and Cons of living with an EV.

  • jkavanagh jkavanagh Posts:

    Yeah, when this entry was originally posted we experienced a technical snafu that carried the comments from an earlier entry over to this one. Any comments that were posted for the few hours before the fix was implemented were lost. Sorry about that, guys.

  • stevezzzz stevezzzz Posts:

    Good strategy, Jason. Superchargers change everything when it comes to cross-country driving in a Model S. In the bad old days (i.e., last summer) the strategy was to drive much more slowly than you'd normally do in a gas-powered car because arriving at the next charging station with more charge 'in the tank' reduces the amount of time you'll have to spend charging, by much more than the time you can save by driving faster. The rule of thumb for optimizing overall cross-country speed used to be, "Don't drive at a speed faster than the rate of charge at your next station." When the maximum rate of charge (at an RV park, say) is 30 miles of charge per hour, you'll actually get from A to D (with stops in B and C for charging) faster by driving really slowly. As a practical matter, nobody's going to drive 30mph on the Interstates, obviously, but 55-60mph was a good compromise between not being run over and getting where you're going in a reasonable time. Now, with Superchargers capable of charging rates up to 300 miles of range per hour (and more), the whole calculus has shifted. You can't drive fast enough, legally or practically, to optimize cross country speed using the old rule of thumb. So the new rule of thumb is, "Take on enough of a charge to get to the next Supercharger with a comfortable margin, given the speed you want to drive and the conditions." With experience, you can start shaving that margin, but adding some extra miles of range costs you so little in terms of time, it's not worth getting worked up over. By the way, there is an online app, EVTripPlanner.com, that does know how to factor in terrain and weather when planning trips, for a variety of EVs. Tesla has also said it's working on an app for the Model S that does the same thing; the good news is that, when it's ready, we owners will get that new software delivered, over the air, straight to the car.

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