Minimizing Travel time with a Tesla (and Bolt)

Ok this is probably pretty obvious to Tesla geeks, but it took me some time playing with ABetterRouteplanner.com to really understand how to minimize the time you spend waiting around. The big things are to minimize the power consumption

TL;dr

You really want to draft behind big cars and realize that going from 75mph to 80mph for instance really increase power consumption, sometimes it is better to go 75 mph behind a big pickup then 80 mph by yourself because you will just have to spend more time at the charing station.

The same is true with hills, these cruise controls are really a little bit silly because in an electric car, it can definitely pay to do 55 mph up hill and limit your draw to say 30Kw and the go down hill at 75 mph where the draw is 10Kw particularly behind a truck.

At home before a trip tickle charge up to 100%, then during the trip visit a super charger when you get down to 10% and then charge in 40 minutes up to 80%. This will minimize your time and visits to the charger.

If you have a short trip and can make it home, then the last visit can be from 10% to 50% which will take 20 minutes.

The Details

As Teslapedia explains:

  1. You want to start with a full charge at home using trickle charging because that last 10% is super slow
  2. You want to be at a minimum charge consistent with safety, so the lower the better. Tesla recommends 12% remaining and 15% is considered a lot. For a 100KwH battery, you get use bout 333 kWh per mile or you get about 3 miles/KwH.  Translating all of this 12% is 12KwH or about 36 miles or range left.  They recommend a maximum of 15% for minimum time spent charging. We use 20% because having 60 miles left feels more comfortable 🙂
  3. You do not want to be next to any other Teslas. That’s because the A and B station actually share 140Kw, so if you are next to another “hungry” Tesla you won’t get your 120Kw maximum
  4. You then want to charge quickly. The rules of thumb are that it below 10% to 25% you get the full 120Kw maximum will take only 12 minutes that is it adds ?!. That’s why you want to get the charge down as low as you are comfortable.
  5. The charge then tapers off so if you want to go from 25% to 50% it will take an 28 minutes, get the picture, it is really slowing down.
  6. Then from 50-80% if will take another 30 minutes. The net is that you get a huge bang from buck from 10 to 25% and then you should only get what you need up to 80%. That is just just enough to get you to your destination with a reserve (eg 20%).
  7. Then it slows down, you should not charge more than 80% at a Supercharger because it is a waste of time, so the game is to go down to 12% and then back up to 50-80% each time and this will minimize the time at super chargers.

The actual curve is a little complicated but from some actual data, you can see how the charge rate seems to fall roughly linearly between 50 to 90% falling dramatically from 115Kw to 30Kw. Then you see there is an even steeper curve for the last 10% falling from 30 to zero.

Note that charging here shows a much lower curve at the beginning, that’s because this was done in Indiana when it was cold. The battery is optimal at 70 degrees F so look at the top curve as what you would get in normal temperatures.

But what about the Bolt? About the same strategy

Well where we live there are very, very, very few Fast DC chargers, so I’ve never had a chance to use one. But Bro9999 has done some research and the results are similar if slower:

  • Most CCS stations are 50kW maximum and when the Bolt battery gets to 75F, then you should see 46kW/125Amps (this is actually).
  • At 50% SOC it tapers down to 38kW/100 Amps and then at 70% to 24kW/60 Amps, so the same rule applies, you really want to keep it in the 10% reserve (24 miles) to 50% range to minimize charging time. Note that the Bolt at 239 miles and the Tesla X 100D at 289 miles have about the same range, so this translates into 28 mile reserve going to 140 miles, so you can go about 100 miles. This takes about 30 minutes which is essentially the same as the Tesla (28 minutes).

Net, net the numbers are basically about half which makes sense given that the Tesla has a 100Kwh battery vs 60Kwh in the Bolt and the charging speeds are about half at 115Kw vs 46kW and the taper points are similar.

However, given that there are few CCS and these cost money (compared with the charge is free for the Tesla X), most of the time it makes sense for the Bolt to stay in the 239 mile range and home charger at 7.2kW (240/30 amps) which is the maximum for the Bolt onboard AC charger. The recharge time is typically overnight.

At destinations, it makes sense to either find a free Level 2 charger at universities or to buy the $400 (even with a $160 discount it is pricey) Level 2 to Tesla adapter this handy gizmo has a Tesla receptacle on one end and a Level 2 CCS on the other.