Unusual charging on a 5,000 mile electric car road trip


Rounding out my 3 part series on doing a 5,000 mile international road trip in a Tesla, I talk about the times I used slower chargers. The world installed vast numbers of slow chargers at huge expense in a giant waste of money, but they do have virtues on a road trip, and eventually all hotels will have them. On a road trip charge and range become very important and sometimes they save the day.

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An interesting view of this subject from a US perspective.

I would add leisure facilities (movie theatres, gyms, etc) to places where there should be a row of 50-100kW DC chargers for those who can't charge at home or work.

If you can't charge at home or work, yes you will seek places you stop for 30-60 minutes. Movies usually mean a 2 hour stop (does anybody even go to those any more?) which is too long for 50kw chargers, but you can design them to let 2-3 cars plug in and charge in sequence if you want to go there. Problem is movie theatres are mostly popular at night. The ideal location of a charger will see use all day long, and for that, grocery stores are the obvious win. People go to them regularly, they drive, and they spend 30 minutes but not more than an hour. Gyms might be a decent choice though usually people spend an hour there, which is a bit too long.

A key error many make is they presume people want a "full" charge. Nobody ever does a full 0 to 100% charge, a full charge is actually from 20% to 80%, or about 35kwh or less on a city car. But normally you don't want to let it get down to 20 if you can't charge at home or work, so you may want more like 20-25kwh. Which is under 30 minutes on a 50kw charger if it can do full rate.

It's OK if you don't have to unplug your car as soon as it's done. Most fast chargers are designed to require that, but future ones can and should be designed with extra cords so you don't have to do that.

I regularly charge at the supermarket for free. Nominally it is 50 kW DC (there is also 43 kW AC but the Tesla is limited to 11), and I usually get about 35. Ideal.

Why do you say that no-one ever charges to 100%? I‘ve done it a few times.

I should say that I am in Germany. 230V three-phase power is in every house. Usually normal plugs are 16 amps (some older ones just 10) and most houses have mostly one-phase plugs, but not all are on the same phase (which can make ethernet over the power lines a bit tricky). Home chargers are usually 11 kW (e phases at 16 amps and 230 volts), but even a normal plug will give 3.6 kw, which is often enough for overnight charging.

I bought my house from an electrical-hardware guy, and there is a three-phase connector in the cellar. Unfortunately the garage is not connected to the house and has no electricity, but that might change. At the moment, though, I don‘t need it.

Free charging at supermarkets is a bit of a prisoner‘s dilemma for the supermarkets: no matter what the competition does, they are better off offering it (the increased profit more than offsets the cost), but if all offer it, they generate less profit than if none offer it.

It is easier when the base voltage is up higher like that. I was not aware everybody had 3 phase, not ever having seen anything but the standard plugs. 3.6kw is definitely enough. With 3.6kw the typical driver might find they need to top up at a fast charger 1 or 2 times a year, making it non-economical to spend a lot to put in a 3-phase.

We talked about those free 50kw chargers -- those are rare here (I used some in British Columbia) and I would have to imagine over time they will go away, but I could be wrong on that. Germans pay about 30 cents/kwh, and if people are going in there for 40kwh fill-ups, that's 12 euros and is an expensive perk for a grocery store or restaurant to give. Particularly with the large cost of installing such chargers. Level 2 is much easier to give for free, but also not very useful.

However, yes, in the future, you should see grocery stores perhaps offering 50kw charging at cost. I predict though, that most drivers will be able to charge at home or the office -- leaving only those who park on the street and don't park at an office or commuter lot during the day as strongly in need of fast charging. That becomes less something you must have to get customers, but there will be a segment of customers who will choose their store based on that.

Essentially all buildings have three phases, but most plugs are just one phase (but not necessarily the same one). Some heavy-duty appliances tap into more than one phase.

I have also charged to 99% a few times on road trips when I knew I had the need. The reason "no one" (really meaning it is rarely done) does it is that it takes as much time to go from 90% to 100% as it does to go from 20% to 60% and cars will warn you to not do it very much, for good reason, though it's better if you are going to immediately drive after the charge so it doesn't stay at 100% for long.

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