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.