On long trips, the Tesla navigation automatically incorporates when and where to charge. It’s a great feature. It’s quite smart.
On the drives to and from Gulf Shores, Tesla recommended stopping many times to charge up. We could have done the whole drive in one or two stops, but it said to make four or more. I assumed that was a bug. It was not.
More physics! Batteries charge more quickly when they have low charges going in. The difference is large – it charges around 200 kW at 20% and below, it charges at under 100 kW once it reaches 50%. The multiples are big. (The same logic applies to your smart phone or any rechargeable battery.)
Although you lose time by making more frequent stops, you make up that time by charging up more quickly at each stop. That is, you’re better off doing a series of short stops, each time charging to 50-60% than stopping only a few times and charging to 85%. The gains in charging time offset the losses of more stops. Charging from 20% to 50% takes 10 minutes, charging to 80% (twice as much charged added) takes 30 minutes (three times as long).
Here is an example, driving from Atlanta to Boston. Making frequent stops shaves about 20 minutes from the 2.5 charging hours needed (about 13% better).
| Metric | Frequent Stops | Full Stops | Difference |
| Number of Stops | 9 stops | 4 stops | +5 stops |
| Total Charging Time | ~78 min | ~127 min | 49 min faster |
| Total Overhead Time | 54 min | 24 min | 30 min slower |
| Total Time Added | ~2 hours 12 min | ~2 hours 31 min | ~19 min faster overall |
| City, State | Frequent Stops | Full Stops |
| Greenville, SC | Charge to 65% (12 min) (6m charge + 6m overhead) | (Skip) |
| Charlotte, NC | Charge to 55% (14 min) (8m charge + 6m overhead) | Charge to 85% (40 min) (34m charge + 6m overhead) |
| Greensboro, NC | Charge to 50% (14 min) (8m charge + 6m overhead) | (Skip) |
| South Hill, VA | Charge to 50% (15 min) (9m charge + 6m overhead) | (Skip) |
| Richmond, VA | Charge to 55% (15 min) (9m charge + 6m overhead) | Charge to 85% (41 min) (35m charge + 6m overhead) |
| Fredericksburg, VA | Charge to 65% (14 min) (8m charge + 6m overhead) | (Skip) |
| Newark, DE | Charge to 50% (16 min) (10m charge + 6m overhead) | Charge to 85% (38 min) (32m charge + 6m overhead) |
| Hamilton, NJ | Charge to 55% (15 min) (9m charge + 6m overhead) | (Skip) |
| Greenwich, CT | Charge to 60% (17 min) (11m charge + 6m overhead) | (Skip) |
| Hartford, CT | (Skip) | Charge to 75% (32 min) (26m charge + 6m overhead) |
On the other hand… the “frequent stops” strategy is more ‘brittle’, as there are more opportunities to get delayed by traffic.
And this effect is bigger the longer the drive. Since the initial charge is a large share of the total distance, starting with a full charge for a shorter drive makes a big difference. For our actual drive from Gulf Shores to Atlanta, it was probably a wash either way.