On an EV road trip, how long does it take to charge? Here is an actual sample: On this recent round trip of 727 miles each way we stopped for Fast DC charging 8 times. Your mileage may vary depending on your vehicle, weather factors and your driving style (speed) but in this instance the stops were of from 20 to 41 minutes in duration. The average was 25 minutes per layover.

Row one in the list below was an anomaly. The in-vehicle planner was a tad optimistic at the Colonial Heights Supercharger (see row 2). The planner said “good-to-go” but shortly into the final leg it was evident that we were skinny on energy. It is a very bad feeling in the gut to sweat [the] fuel. So, rather than stress out about it we made a very quick pitstop in South Hills. Had we lingered the extra minutes in Colonial Heights the 8th stop would have been totally unnecessary. Filtering out the goof for a perfect run we would have made 7 stops for an average duration of 28.5 minutes per stop.

Nerd-out on the tabulation if you will and note the Start and End percentages. Key to Fast DC charging is to arrive at the charging location with the battery state of charge (SOC) ideally at around 10%. This value is listed as the %Start in the table above.

The following table shows the charging behavior at a fast DC charger.

Observe that the battery can accept the maximum Fast DC charger output if the beginning SOC is low i.e. less than 25%. After 25% as depicted, the charger output gradually diminishes.

The charging curve or Taper, as it is known, is hard coded to protect the life of the battery. Included in the chart are v2 and v3 Superchargers for comparison contrast. At ~150 kW and around 45% SOC the charging curves merge. (click on the charts to expand) Requisite is a pre-conditioned battery (warmed up).

Lingering beyond the necessary %End charge significantly increases your off highway time. The graph shows that the Taper flatlines from 66 to 80%. All the way to 100% SOC is very slow charging. Plan on a 1 hour plus wait and possibly additional fees to achieve a top-off. It is more efficient to bring the SOC to 60% and then continue on to an intermediate stop than to take the delay going for a full battery. Arrive at the next stop with 10% rinse and repeat.

By comparison contrast an AC charging curve typically flatlines for the duration as depicted below:

The output of an AC charger is miniscule compared to the massive flow of Fast DC. At these output rates (6 to 11 kW) there is no risk to battery health. The duration of charge at an AC charger is considerable and is best utilized at destination for an overnight refill.

Public Level 2 (AC) chargers operate at 208v. This is because commercial building sites use 3 Phase power. A Level 2 charger at your home is Single Phase, so 240v

In my previous post I presented a descriptive view of pre-trip planning. In this post you’ve just reviewed the actual trip as it played out. We took on 484 kW at the 8 Supercharger visits with a total cost of $191.99 or an average of $0.39 per kW/hr. We were on the road for 30.5 hours. Actual time plugged in was 3.3 hours. Figure conservatively, an additional 10 minutes of off-route navigation for each station for a total of 4.6 hours for this EV care and feeding statistic.

Data points captured with Teslamate open source logger.

Leaving one’s comfort zone on a longer distance trip requires some forethought. Where to charge and how far can I go between them, how long does / will it take and when are we going to get there.

Buzzing around the community, running errands, short hops are the majority of trips that you do. Planning is nil. At days end the car is plugged in and it charges overnight; ready to go by morning.

Leaving town: North Carolina to Massachusetts est. 700+ miles

Here’s the plan… there isn’t one

No need to go through the machinations of planning! Tesla has functionality that does it all. Enter a destination into Navigation and after a moment a route with stops is generated which displays on the map interface. Temperature, wind, slope, traffic are baked in.

Here’s the plan

Before Tesla’s app became polished and bullet proof, I used A Better Routeplanner (ABRP) an app that was/is quite good at making a plan. It is nice to have an advance look. Study and plan tweaks are best accomplished from the ease of your desk vs loaded up in the driveway anxious to get moving or later enroute with traffic concerns demanding full attention. There’s a graphical map presented along with turn-by-turn as one might expect. Here is a useful ABRP output detail .

Focusing on the column header, SoC (state of charge) in the summary table indicates that we are departing with 75% battery and will arrive at Colonial Heights, VA the first charge stop. This first leg is 149 miles and after an estimated drive duration of 2 hrs and 16 mins we arrive at the Colonial Heights Supercharger with 17% SoC. We are targeting 54% SoC so after a 16 minute stay we disconnect and depart for the next and so on.

Nice to know tidbits such as energy used , cost , trip distance/duration and predicted ETAs are tabulated. It is important to note that these data points, being estimates, are subject to variation. In other words, your mileage may vary. Increasing driving speed more than X above the posted limit is the biggest influencer.

Set intended speed of at least 105% in the ABRP option section.

The inevitable bumper to bumper crawl from a rush hour commute or fender bender lane closure will (no pun intended) impact the estimated time of arrival. Note that traffic tie ups do not have significant negative influence on battery range.

Learn more about: Range Anxiety – Energy Consumption

Planning on paper is subject to happenstance so for the real world add some extra energy at stops (for Mamma). Plan for the unexpected. Inform friends and family that your ETA is X but add in a 60-90 minute fudge factor. Plan ahead but plan on plan revisions to the plan. You have a plan.

With v. 12.5.5.2 Tesla’s vision based autopilot (supervised) the emphasis is on driver supervision, still. While autosteer and adaptive speed control has become relatively polished and worry free there are edge cases where driver intervention is necessary/mandatory.

One might think that the driver, after having made a manual course correction or driving adjustment, would “teach” the car. Future revisits to that kink in the road would then go smoothly but Tesla’s system doesn’t work that way. At the end of the day, reams of video clips upload from the vehicle cameras to mothership — Tesla’s neural network.

Pulling data (last 30 days sample) from vehicle (as a network client) transiting my network to the NN uploaded: 71.6 GB

Autopilot behavioral changes and improvements come from Tesla’s end-to-end AI training system, code named Dojo, via versional updates downlink to the fleet. In this my car (and all cars) becomes smarter. What needs to be smarter? Safety, always of course, but key on the list is the ability to flow naturally with traffic and mimic driver behaviors good or bad. For instance:

The “Hollywood Stop” aka rolling stop might be considered bad but most people do it. Autopilot is not permitted such liberty. It comes to a dead stop before proceeding and this is slightly irritating but lawful.

Along this vein, the NHTSA stop, where one comes to a complete halt at the white painted marking at a stop sign before edging forward to see traffic and proceeding. Good form but unexpected in the common place sense.

While at the intersection, number 1 at the traffic light signal, turns green. Go. Defensive driving used to be taught but people seeing the green light step right out. Autopilot waits a split second before proceeding. It’s a minor irritation, and I haven’t had anyone from behind impatiently sound their horn yet (but I know in certain parts they surely would). The pause is good. Drivers with the green should look for oncoming. Autopilot has been hardcoded to know that cross traffic frequently will fudge run the red light.

Not wanting to be labeled as one of those Hypermiling roadie types, I still like to begin a coast down as I approach a traffic light that has turned red. Aggressive drivers usually charge right up until the last moment before braking. This avoids the dreaded cut-in and unfortunately autopilot mimics this. I would prefer that autopilot would rely on re-gen to decelerate and minimize use of the friction brakes. Conversely, without traffic, autopilot accelerates from stop signals like a jackrabbit — way beyond Chill.

v. 12 autopilot dictates what it considers to be a safe rate of speed based on conditions and environment. Previous iterations of FSD would rely solely upon and match posted speed limits. But now, the car dawdles on some stretches sometimes doing 10 mph under. I know other cars in trail are thinking “Sunday Driver” or little old lady that can barely see over the steering wheel. You can poke the accelerator pedal a bit to help with the confidence I suppose. So much for the annoyances.

Intervention: the need to take charge, assume control, over-ride the automation. Save the day!

More seriously, and Tesla does require users to acknowledge the need and requirement for supervision, there are edge case where autopilot has low confidence or encounters a situation for which it can not deal without help. In safety situations autopilot (hopefully) recognizes and alerts the driver with an audio chime and a take immediate command text exclamation. A situation is imminent (1-2 secs.) and if the driver has not been attentive there could be consequences.

The Handover: automation off, manual control on, is fine when the human operator desires but when it happens unexpectedly because of autopilot initiative the human can be momentarily caught off guard. A surprise transition is messy.

Luckily, these are now rare. The vast majority of intervention occurs when the driver’s comfort level is close to being exceeded. e.g. the vehicle cuts a corner, or threatens to curb a wheel. In such a circumstance driver takes control by disengaging.

Disengagement (driver induced): press the off button, tap the brake pedal, or for the most immediate action; yank on the steering wheel

A disengagement by manual steering will literally cause the autopilot to take embarrassed offense by posting a text to driver: “what happened/what went wrong?” Optionally the driver can respond with a haptic press on the microphone and give a short verbal complaint. e.g. “the car lost situational awareness in that turn and assumed the incorrect lane”. This, along with associated before/after video clip sequence capture, goes to the engineers for review.

I wish there was a way to similarly send kudos or an attaboy. Occasionally, autopilot does something unexpectedly brilliant. Recently exiting a parking lot with a construction barricade just prior to turning right onto the highway required a hard 90 degree turn which the self-driving accomplished with low speed steering full-lock all while maintaining lane discipline. I was primed to takeover because I was skeptical for the outcome but no need. Later, also a 2 lane road, I spied debris (a small branch and leaves clump) in my path and seeing it coming put my hands on the wheel when I felt autopilot do the nudging and offset ever so slightly right to avoid contact. Very subtle and I wanted to applaud.

There are other features with v. 12 that I am experiencing such as Autopark. More than a party trick (i.e. Summon) Autopark is cool and works well consistently backing into the white lined bounded box centered and without any involvement. When its time to leave the parking spot autopilot knows in which direction you want to go. i.e. if you backed into it you probably want to pull out forward when leaving it. Autopilot automatically selects forward ‘gear’ saving you the effort. (As supervisor, verify and confirm the selection of course)

There are times of despair when you say don’t take away the steering wheel just yet, FSD won’t be happening anytime soon, and not ready for prime time. You feel like a beta tester and wonder how they get away with selling this Full $elf Driving option. The manufacturer should be paying ME to be the early adopter helping with the machine learning. I do feel like I’m riding herd with a 15 yr. old with a learners permit coaching / anticipating everything.

The next FSD version 12.5.6 and within a short time (Elon time) v. 13 there are to be significant changes.

With FSD version 12 my driver job is quite secure. It is more fun to drive than to watch it being done and less stressful. I’m always comparing technique and so far I can still say I’m much smoother and more efficient at it. Never the less Technology is a wonder and it is exciting to be a first hand observer of this innovation and progress.

Trust (but verify)

Self driving cars are a few years away. Letting Autopilot take control is like watching an inexperienced beginner on a learner permit. Fortunately, as a monitor (with skin at stake) you can gently intervene or abruptly take-over if the performance is not to one’s liking.

Current state of the art tech with Hardware 2.5 does quite the job centering the vehicle in the lane and maintaining proper distance from the car ahead with adaptive speed. Today, on an extended drive, I was able to sample test the latest enhancement: Navigate on Autopilot (beta) which further extends Autopilot.

Following GPS guidance Navigate on Autopilot suggests lane changes required for the route. Using cameras and forward radar it also recommends an open lane when overtaking a slower vehicle. You, as second pilot, acknowledge the suggestion and give permission with a tap on either stalk on the steering column (ignore is the default). In actuality you are babysitting the proceedings — and like a hawk.

There isn’t, nor should there be any trust expectation between you and the machine. The manufacturer (and his lawyer) feels the same way. Beyond any disclaimer you need to be attentive. The reason is called the automation hand-over. The autopilot can, after the briefest of warning, signal bailout and return control. If your head is not in the game this transfer could be messy. So, autopilot continually confirms that you are standing by. If you’re not detected actually holding the steering wheel you are politely prodded before it becomes serious. The system shuts off / locks out an abuser ignoring any cautionary nags.

The autosteer function continually saws back and forth ever so minutely seemingly testing to see that it has not been abandoned. A sensitive passenger may perceive the motion but in comparison to earlier iterations it is fairly smooth going.

Hardware 1.0 was primitive as autosteer would ping pong on secondary roadways hugging the inside line or wandering inebriated opposite. Still, it was exciting to experience this alpha software. Realizing that the future had arrived inspired anticipation for FSD

Lane keeping on today’s trip was quite good during the Interstate portion. There were some, shades of yore, one spurious blip of regen, a wander noted in the tight radii of an exit ramp. A little faith was required but no boundaries were exceeded. I did wonder what any closely following driver might be thinking.

whoa boy (too wild)

This happened… A mowing tractor pedaling the shoulder as fast as he could go — hazard flashers blinking but protruding somewhat into the right lane. Autopilot decelerated for the detected obstacle as it should do. I switched off auto steering and moved to the left lane to pass which was occupied by a truck just ahead. During the maneuver, just as I started over Autopilot saw daylight between Mower and Truck and (adaptive cruise control still engaged) accelerated harshly. Splitting lanes like some deathwish motorcyclist would have been a bit too sporty.

push nudge (too timid)

Autopilot slows as necessary for a vehicle ahead which is turning right onto a crossroad. Ordinarily, a driver can safely resume speed accelerating in anticipation of the other vehicle clearing. Autopilot delays this for a count of 3 before getting on with it. It seems like an eternity because know that the driver(s) behind have lost patience.

advanced nav (passed)

One part of the route today is considered tricky even for an experienced operator. I have traversed it many times and decided to let the student driver have a go. The course begins with an off ramp exit, followed by a double merge, another exit, a sweeping loop where traffic sometimes can crawl or even halt, and then yet another merge — all rapid fire. Autopilot has to steer navigate and sequence with the merging vehicles. It’s the full deal. Tight choreography. Autopilot will slow to make a merge opportunity happen but doesn’t offensively overtake for a cut-in. 

Eventually cars will computer interface with each other and the dance sequence will be safe and carefree. Until then, it’s student learning so; mind how you go. It’s early days yet.