Carmakers and charging stations have been engaging in a “mine’s bigger than yours” competition with their high speed DC charging stations. Tesla TSLA +10.8% paved the way by installing a network of 120KW chargers which later were upgraded to 150kw. Porsche demonstrated a 350KW charger for its Taycan. Tesla upgraded its newest stations to deliver 250KW. Non-Tesla networks started with 50KW stations, but as the CCS charging system improved, new deployments, particularly on the “Electrify America” network have gone to 150KW with a few even higher.

The installation of “Level 2” chargers (which run from 3KW to 8KW) turned out to be misguided, filling the country with expensive charging stations which drivers of more recent long range electric cars almost never use. Those chargers are slow, and either free or overpriced. They only make sense in homes, work parking lots and hotels — places people routinely spend 4 or more hours. A lot of them ended up in places where people spend 30 minutes to 2 hours, like store parking lots.

Each KW will add about 4 miles of range per hour of charging, so a 150KW station, when going at full power, can theoretically add up to 600 miles of range in an hour to a car like a Tesla model 3.

Except it can’t. That’s the instantaneous rate, but that rate is only delivered at the start of the charging session, and once the battery gets over half-full (or even earlier) it drops. It might be closer to say it can add 100 miles in 10 minutes, but only on a highly-discharged (empty) car. It can’t add 200 miles in 20 minutes. Most cars only have 200-300 miles of range anyway.

Are we getting it wrong again?

Could similar misconceptions be driving the deployment of fast charging? The peak-wattage contest above is driven by what I call “gasoline thinking,” which comes when you compare electric car charging to gas stations. With gasoline thinking, you imagine you will be driving along, notice you are low and look for a “filling station” where you will plug in to top up as quickly as you can.

Electric thinking is different. There you want to charge while you are parked for some other reason. The best reason of all is sleeping, ie. in homes and hotels. With this method, you don’t care how fast the charging is, as long as it can get the job done during your stop. When you go to a gas station, your primary task is to fill up. EV charging should, ideally be your secondary task.

This is not to say that super-fast charging isn’t desired from time to time. There are times where you have no primary task to do. All other things being equal (which they aren’t) you certainly would like it to be faster. If they got it down under 5 minutes, it would compare with the gas station. There are places, like a lonely truck stop on the interstate, or a delivery fleet depot, where this is good.

All things are not, however, equal. Really high power charging is expensive to install. The charging stations are expensive, and getting megawatts of electricity into facilities is expensive. (Not as expensive as building a gas station, but still plenty.) That cost has to get paid, and usually the price of electricity at these locations can be anywhere from 2 to 5 times what you pay at home. Imagine if you could fill up at home for $2.50/gallon but the gas station on the highway was $8/gallon? Guess which station you would avoid unless absolutely necessary.

Secondly, charging at very high rates reduces the lifetime of your battery. It’s hard to pin down how much in dollars, but it’s real. Many companies are working on chargers and batteries to reduce this, but for now, you only want to do it if you need it.

For people who can charge at home, or at the office, that should still be the #1 choice for charging, and it can be done at low speed with fairly low cost equipment. Indeed, the much derided “level 1” charging, at only 5-7 mph may often be the right choice. If an office can put in 5 low-power chargers for the cost of one Level 2 charger, that might be the better choice since most cars travel only 40 miles/day. A smaller number of Level 2 can serve the subset of people who need a little more that day. (It should be noted that slower charging at 2KW Level 1 is modestly less efficient than 7kw Level 2.)

People who can’t charge at home or work, or people on road trips, need a different solution. Today that solution is generally the supercharger, at least for Teslas.

“Fairly Fast” charging

The answer may be to increase the deployment of what we might call “fairly fast” charging, in the 40-50kw range. These chargers are currently much too expensive, but not nearly as expensive as chargers of 150KW or more. There are efforts to bring down the price as well. I recently spoke with “Wallbox,” a European supplier who, while they would not yet name prices, plans to produce significantly cheaper 50KW chargers.

The cost of the charger is one thing, but the cost of bringing in high powered electrical service is also considerable. Even for an existing commercial building, adding hundreds of KW can require new electrical service and expensive wiring. 150KW is major juice with major safety risks, and that means cost.

You want “fairly fast” charging in the places where you will stop for 20 minutes to an hour. Places like restaurants, grocery stores and other major retailers, bars and meeting places. If you can get it cheap enough that it’s everywhere, it becomes a very simple process when visiting the store. It must be super easy — just plug and go, with a data protocol arranging billing right through the cable. If the store wishes to subsidize it, it should be doable by just tapping your phone on a validation dongle in the store, or even better, automatic with a digital payment at the store.

Fairly fast is also fast enough for road trips at restaurants. Even fast-food sit-down dining takes around 35 minutes for a group. The biggest problem with restaurants is they tend to do almost all their business at lunch and dinner, so road trip charging at high rates still serves a purpose. Because you must park at the charger, it is better to have chargers at restaurants than a large charging bank that is a 5-10 minute walk from the restaurants, unless there is a dining area at the charging bank for take-out.

Available power charging and RV parks

As noted, the cost of new electrical service can be a problem, particularly for a small establishment just wanting to put in 2-3 stations. Once you are building a large charging facility you are almost always putting in new electrical service.

What’s needed is fairly fast stations which are designed to monitor the total current coming into the facility, and which then never give out more power than the existing circuit can handle. Many buildings are very well provisioned, and only use a small portion of their electrical service most of the time, only using more when AC need is very high. The rest of the time they have lots of spare power.

Current electrical codes have the electrician add up the loads in a building and apply a formula to them, and this calculates the size of service that is to be installed. This formula works hard to avoid any overload, and while it’s not simply the sum of all the loads, it does presume that many of the loads might draw their full demand at the same time. That can happen with dumb loads, but it’s easy to make a car charger which responds to other loads. It can see that something else (like the air conditioner) is drawing a lot of power, and reduce how much it uses so the total stays within safe limits. Our electrical codes are only now adapting to the idea of smart devices which can do things like this, but they eventually should have no problem with this approach.

In reality, a decent sized commercial building (like a store) putting in a 50KW fairly fast charger would almost always have power for it. However, there might be a few times it doesn’t. This would slow charging down, but if that’s rare enough it’s not a problem — and it saves a lot of money compared to upgrading electrical service for those rare times. These times are also predictable in most cases, since we have reasonably accurate temperature predictions that can tell you when it’s likely that available power will be lower. Drivers who use an app to search for charging will be told that a charger is going to be at lower capacity long before they get there.

A low cost fairly fast charger which doesn’t require an electrical upgrade (even if you put in a few of them) could be a winner for retailers. While it could also make sense at offices, it adds the burden of employees have to come out and move their cars to share the station. The typical employee will need perhaps 10-15KWH in a day. You could have 1 fairly fast charger which could serve perhaps 20 employees if they keep swapping out, but it might be much easier and even cheaper to just have 20 Level 1 chargers that take the whole workday. Also possible is what might be called a Level 1.5 — 208 or 240 volts at 15 amps. A simple EVSE at this level (technically the low end of Level 2) is easy to make and even can be wired on existing conductors for very low cost install, but works double the speed of regular Level 1.

RV Parks

RV parks are another interesting opportunity for cheap chargers. RV parks tend to have very high power electrical service, because they need to handle the park being full on a hot day with air conditioners running in all the RVs. When that’s not what’s happening, they have plenty of spare capacity, and they could install dynamic chargers if they came at a low enough cost. Today, fast charging stations are almost exclusively located on major highways, not out in the more rural and backcountry areas. RV parks, however, are almost everywhere. A lot of people prefer to road-trip on the back roads.

EV drivers would love the idea of no part of the road system being off-limits due to range, and they even use RV parks (at the very slow level 2 speed) today. There may not be much to do at a typical RV park in a 30 minute stop, though there are always picnic tables to have a take-out meal. Yes, people would in this case crave gasoline-style fast recharges at 150KW or more, but for now, that’s too expensive to consider for RV parks. People will tolerate needing 1-2 half-hour stops per day if it gives them the ability to drive these rural locations they otherwise could not drive at all.

The important message is to stop thinking the way we did with our gasoline cars. You want to understand where people actually will need energy, and where they will stay long enough to get it from different speeds of chargers. You have to consider the costs of the chargers, and may find that more, slower chargers makes more sense in some places, and medium and super fast chargers are right in others. Or in many cases, the answer may be a mix.

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