As EV deployment grows, we’re starting to see Level 2 charging stations which fill up. A new driver arrives and can’t plug in. Sometimes they really desperately need to charge, other times they figure the earlier cars have had enough and its their turn. The video above, caught on a Tesla TSLA “Sentry” camera, shows another driver unplugging the Tesla to charge his BMW. Such actions cause a great deal of debate in the EV community. Is this a good idea, or beyond the pale? When should it be allowed or encouraged?
For most of EV history this was not a big issue. A lot of charging stations were installed for a small number of cars in need. Only a few of them get fully occupied — mostly free stations or stations in particularly popular parking lots. It should not be that much of an issue today, either. For the vast majority of drivers of modern EVs with 200 miles or more of range, you never have to use level 2 stations around town. Charging at home, your car almost always has more than enough for a day’s driving around town, and your home charging is usually cheaper than any commercial charger, excepting free chargers of course.
This large block of Level 2 charging stations is full — a rare situation but in need of a solution
As such, for any city charging station a simple rule should be “don’t use it at all if you don’t need it to get to your destination with 20% or more charge” for any charging station likely to face contention. Many people already follow that rule on their own, except for free stations which people find hard to pass up. We all love free. If they did follow this rule, contention for most stations would be pretty rare.
Alas, it doesn’t work that way, and there are also stations with legitimate contention, in employee and commuter parking lots, and at hotels. In those places you overload a station with people who all have strong need of a charge.
To sum up the conflicting issues:
Of course, the easiest fix is to put in more units at high-contention locations. If they are commercial stations, this can make financial sense. While typical stations don’t pay for themselves as a business, ones that are regularly full can do it. Stations are also programmed to limit charging session time, or to charge extra money if you stick around too long, particularly after you are full. They often do that even if nobody else wants the station, which is annoying and counterproductive.
Some stations are designed so the cord will reach 2 or even 4 parking spaces. Less commonly, there are stations which actually have multiple cords, but can only charge one car at a time, or share charging power among the cords. These are a great solution most of the time. Employees who charge only at work, and not at home, still mostly need only 1-2 hours each day from a Level 2 charger, but having to coordinate sharing the charger is cumbersome, and can involve people having to come out and move their car twice during the day. Unfortunately, multi-plug units are rare.
It’s generally viewed as bad to unplug a car. On the other hand most people would be quite pleased to allow somebody else to transfer the plug if they have gotten enough and the other person has strong need. Almost nobody has a problem unplugging a car which has finished charging, or one which has hit the maximum time limit for the charger. (Indeed, cars that sit there after charging stops are considered almost as bad as the most hated cars of all, namely gasoline cars who “ICE” a charging space.) It is often possible to tell if a car is still charging, because many have an indicator light which shows this, but not all. However, with more models of car out there, nobody will know where the indicator is on each model, or how to read it. For chargers which charge extra money to remain plugged in once full, the car owner would actually be very happy to get unplugged.
Chargers with display screens sometimes will reveal if the charger is active or not, and how long it has been running. Chargers could go so far as to display “OK to disconnect” when this is true, but I do not know of any which do this.
When plugged into a dedicated Tesla charger, you can’t unplug the charger, even when full. This is a security feature, and prevents theft of things like Tesla’s mobile EVSE as well as preventing unplugging while power is on. The owner of a car can remotely unlock the charge port. When Teslas use the J1772 standard port adapter at regular stations, this can be disconnected like other cars with the mechanical lock, though one can buy a simple lock to prevent that, which unfortunately works even when the car is full. It is also an issue that the Tesla charge door can attempt to close when the adapter is present after the J1772 plug has been removed.
It should also be noted that the European Type 2 charging plug lock is in the car, not the plug, just like Tesla. Unplanned physical unplugging only happens with the J1772 plug common in North America. This ability also means somebody can steal mobile J1772 charging cords which are worth from $200 to $400.
Plug-in Hybrids, which are hybrid cars with a gasoline engine but a battery range of 20-40 miles, create a special debate. Plug in hybrids have no range problem, they never “need” a charge because they can always get home on gasoline. They only charge in order to do more of their miles on electricity — which has both a lower cost and means less harm to the environment. For many plug-in hybrid owners, they charge at home, do their full drive to work on electricity, and charge a bit more at work to do the full drive home on electricity. That’s a good thing, but aside from the fact that they never need a charge, they only ever need a very small charge because their battery is small. It’s not unusual to see plug-in hybrids that were full long ago blocking a charging station. While a plug-in hybrid never deeply needs the charge, frequent charging every 40 miles is the whole reason the owner bought that type of car.
Different etiquette rules get proposed. Some suggest one should simply never unplug another. After all, if that first person needs the charge to get home, you could ruin their day. But if you were depending on it, it might ruin your day just because you got there later. EV drivers would ideally like the situation where a person can’t get to their next destination to be very rare.
The etiquette of “Don’t plug in if you don’t need it” would probably work but is unlikely to happen. People are selfish, particularly with free stations. They don’t want to give up free juice just in case somebody else might come along who needs it more.
A more practical rule might be “If you need this charge, say so explicitly, or otherwise it can be presumed it’s OK to unplug you for somebody who truly needs it.” One could “say so explicitly” with a few potential options:
If the station has support for these protocols it can do a lot. In general, anybody who finds a full station should signal they are waiting with their app or card, and get instructions of whether it might be OK to take a plug that seems in use, or how long they will have to wait. In the former case, the station would facilitate the switch. In general, disconnection of a live session without warning is not a good idea.
You will get violators of course. If somebody does a hard unplug, the station knows it. The station then has several options. If that first driver has said “This is an urgent charge” the station can:
A good place for all of that is the mobile app which comes with almost all charging networks. (Some networks use a tap-card, some take a regular credit card, and free stations often use no authentication.) This can allow communication with the driver of the original car using the station. One approach would be to allow that driver to know somebody is desperate to use that plug, and to accept or reject that request. In fact, many drivers would even be willing to come out and move their car in such situations, which is necessary if there is only one parking space available.
The Chargepoint app is one of the more popular ones for managing a charging session.
Indeed, a good idea in general might be for incoming drivers to, using the same system they would use to start charging, signal, “I’m waiting for a charger.” This could trigger a message to one or more of the drivers that somebody is waiting — starting of course with drivers of any car that is full or has been charging for a long time, or ones who have not expressed that their charging need is essential.
This signal could also do something more — which is initiate idle fees for cars that are full or beyond the maximum charging time. Many stations already charge such idle fees, as a coarse way to discourage hogging of the stations. That can work, but as noted it is quite coarse. Drivers can be forced to move cars to avoid idle fees even if nobody is waiting. There’s no reason to make people come move their cars if nobody else is waiting. Using the app, once could even signal desire for a space before arriving at the station to avoid a wait.
This functionality could also be implemented in the app for the particular brand of car, and there is always such an app. It would be fairly simple to make a system to allow say, one Tesla owner to signal another about their need via the Tesla app. It’s a little harder to made communication work between different brands. A good approach though, would be to have the app scan either the licence plate or VIN of the car in question (or, if it’s alone, get its Bluetooth MAC) and send that to a database that is able to forward the message to the app of the driver of that car without revealing private data.
This is a fancy way of implement what some drivers already do, which is leave their phone number visible to let others text or call them if in need. In spite of heated debate about the etiquette of “stealing” a charging cord, most EV drivers actually like to help each other out. With Teslas, the person reached can, as noted above, even unlock the charge port remotely. (In cases of much greater trust, Tesla owners can even authorize the remote person to move their car through the app. That may seem like a lot of trust but is not unreasonable in places like an employee parking lot where the person hoping for the spot is a known co-worker.)
The long term and best solution is to either have multiple cords and spaces per charging unit, or just lots of chargers. That costs money, of course. In some cases employer lots might find it better to put in a large number of slower stations so that everybody can plug in all day without much hassle. Plug-in hybrids, for example, never need more than a regular “level 1” household plug at 120v, and this can be very low cost to install. In fact, since the average car only drives about 35 miles/day, even all battery EVs are mostly fine with level 1 for an 8 hour workday charge, needing the rarer, faster units only from time to time.
Approaches like the above are needed only on chargers where there is contention, and where a lot of people really need the charger. This is primarily:
Hotels are the strongest case. Today, most hotels do not space out their stations, so there may be only one parking space per plug. An obvious solution for hotels with night staff is to have valet parking at the chargers so their use can be maximized. Guests can be asked how much energy they need and an app can signal the valet when it’s time to swap out cars. This can also be true when the hotel does have more than one parking space per unit — then the valet can just go and move the plugs, as guests don’t want to get up at 2am to do it themselves.t want to get up at 2am to do it themselves.
Still, many things stand in the way of the ideas above. Many chargers, especially free ones, have no screens or no smarts at all, and no app. They can’t help us.
Fast charging sessions are short, and they usually charge high idle fees if people don’t return to unplug their car once the session is done. As such, there is much less risk of contention. In fact, the idle fees are larger than they need be, and an annoyance. Those who dine or shop during a fast charging session may find they have to interrupt their meal to go move the car, even if there are spare stations and nobody waiting. Tesla waives idle fees only if a station is less than half full. Again a system where people can specify that they desire to charge makes more sense, and that can trigger the idle fees if a driver doesn’t move.
Tesla is set up well for this. With Tesla cars, drivers almost always signal they intend to supercharge well in advance by asking the system to navigate to the charger. This must be done to activate Tesla’s “preconditioning” system which adjusts battery temperature for faster charging. Tesla thus knows not only if the station is going to fill up, but when each car will get there. It could warn charging drivers when their space will be needed only when it will be needed, with enough time to get there. Those who forget to navigate to the station might have to wait a few minutes — and will remember to precondition next time.
This is less easy with other fast charging networks. Tesla chargers only have exactly one parking space per charger as the cord is very short. Other DC Fast stations have longer cords and can often reach multiple spaces. In fact, it is very common for those stations to have two plugs — one CCS and one CHAdeMO. They can’t use both at once, but they could do a sharing protocol in certain situations. At least until CHAdeMO fades away.