DC Rapid charge analysis

  *Note:  not quite finished yet, pending more trip experiences

  Most of the time I would charge the Kona at home, like most electric vehicle drivers do, as it's decidedly the cheapest and most convenient option.  My electric service has time-of-use billing, so charging off-peak brings running cost per mile to less than two cents!  Compare that to 5 or 6 cents per mile for gasoline, about the lowest you can presently achieve in an efficiently-driven Prius, and the petro-price only goes up from there.

Long roadtrips done electrically are a different story, and that's the most common situation where DC fast-charging is needed.  This brings up the headache of finding out where rapid-chargers are, which billing network they're on and *how* they bill, as well as which charging protocols they support.  I described the present state, as of late 2019, to colleagues thusly: take a fairly efficient 50-ish MPG car like a Prius, and outfit it with a 5-gallon gas tank instead of the stock 11 or 12.  Now, take away 90% of the existing gas stations, and then try to plan your roadtrip.  Fortunately, there are plenty of apps for that, but without the internet you're basically hosed.  You can't just spot a charging place on the fly along a major highway and pull in.  [It gets even more confusing during any conversation about this, where "charging" can interchangeably refer to 1> pushing energy into the car, or 2> pulling value out of your wallet.]

But the most confusion we encounter is about the electrical standards used for high-power vehicle juice-up.  Put as simply as possible, we basically find three different connector types in the US at this time: CCS, CHAdeMO, and of course Tesla's own proprietary thing.  And that's just the physical plug, where the only feature common to all of them is a pair of big honkin' pins to send current straight into a car's battery.  The data interactions are the other layer of incompatibility, so there's no such thing as a simple passive connection adapter from plug A to car B.

    CCS and CHAdeMO plugs   Tesla plug eliminated
    [Image: chargedevs.com]

Non-Tesla standards seem to be settling on CCS or the Combined Charging System, an extension of the J1772 connector that's been around for a while.  It seems to be slowly gaining ground over CHAdeMO, but the process has not at all been a pain-free one.  This is the result of a bitter battle back around 2010-2011, and it's still not clear how things will eventually settle out.  As many other articles about this have mentioned, it's VHS vs. Beta all over again, and the standard that eventually prevails is likely to do so because of money far more than technical merit.  Frankly, if everyone had adopted the European "type 2" variant of J1772 and its extension to CCS, then we could have traditional Level 2 home charging, faster three-phase AC charging such as in commercial fleet environments, and high-power DC charging all in a single connector.  It is very telling that Tesla is moving toward type 2 CCS for superchargers across the pond, but are still hiding in their walled garden in the US.

In the meantime, US drivers still face an unholy mess.  Charging networks are trying to build out regardless, by simply putting two types of plugs and protocol support on their high-power deployments.  They don't know what else to do, but the infrastructure needs to be installed.  As stupid as it sounds, it's as though you pulled up to a gas pump in your ICE car and the pump had two or three different kinds of fuel nozzles hanging off it, and you had to pick the right one for your filler. High-speed EV charging is also far more complex than opening a valve and letting liquid fuel out.

Connectors have to be able to handle the high currents involved -- 200 or 300 or more amps for a sustained time, and the protocol for any system includes all kinds of lock-step safety and capacity checks.  Cables for power levels at 100 kilowatts and beyond are starting to include liquid-cooling in their design, albeit with a few growing pains.  That's an *assload* of power that we so casually talk about in this field, and it's kind of amazing that a vehicle can just quietly sit there and suck it all up.  Generally the car is entirely at the mercy of the rapid-charger's power supply, which could easily wreak major battery damage if not controlled carefully.  There also has to be a lot of protection against disconnection under load, to avoid destructive arc-faults in connectors and relays.

Tesla and CHAdeMO have adopted variants of CAN automotive networking for their car-to-charger control protocols, but the SAE decided to extend the thinking for CCS to cover the whole "vehicle-to-grid" concept.  This made it inordinately complex, which may be one reason it took so much longer to nail down the standard.  It uses a type of data-over-power-line transport called "HomePlug Green PHY", except that in this usage the data doesn't actually travel over any power connections.  The spec for the lowest-level protocol alone is *seven hundred pages*.  I found a copy here, but it is a bit more manageable to dip into when rendered as a PDF [about 3 Mb].  The spec for "PEV - EVSE" interaction starts around page 671; have fun with that.  The signaling is sent superimposed over the existing J1772 control-pilot line, so as implemented a vehicle supporting CCS wouldn't be able to participate directly in any V2G setups without the charging station doing some translation up to the larger conceptual "smart grid".  For all the blather about it through the 20-teens, we're still a long way from any of that actually reaching reality. 

It's all a work in progress, as I'm sure gasoline fueling infrastructure was in its infancy.


Description of Charge Control Module That aside, we still need a translation layer between CAN from the Kona's BMS and any CCS DCFC that speaks OCPP over PLC on the CP line.  How's that for some alphabet soup?  It is the job of a special Charge Control Module in the Kona to help sort all this out, a unit dedicated only to the purpose of fast-charging.  This is a description of it that I found on Techinfo [click for better detail].  Compare these pics to the unit I found in my own car -- it looks quite different.  The service info is correct about the function of either type of box, however: it serves as the protocol translator between the car's battery management system and an external charger.  And with the way all of the standards pile on top of each other, that is not an easy job.

Block diagram of CCM This will only make sense to engineering types, but it's the basic block diagram of the DC charge controller.  The powertrain CAN bus or P-CAN comes into one side, and radio-frequency PLC gets inductively coupled to the control pilot line out the other side.  This is why I was able to pick up a convenient pilot-line tap right there underneath the box, as opposed to digging around in the underhood wiring.

Prepped with that, I wanted to *see* this in action, so my first foray to a fast-charger was going to include some serious nerding.


Pulled in next to a Leaf There's a Chargepoint 50 kW deployment at a relatively nearby Hannaford's grocery store, so one evening I loaded up some test gear and tooled over there just to play.  I pulled in next to a Leaf that was already using it, so I'd have to wait until its owner came back.  Two plug heads, but only one power supply, usual configuration!  It was a bonus that the charger was free, sponsored by the local power company or something.  I would still have to activate it with my freshly-minted RFID tap-card, as it doesn't simply turn on for any car that plugs in.
Basically, as of 2019, an EV owner has little choice but to sign up with two or three of the major fast-charging networks that serve a target area, and use their RFID card or phone app to enable charging.  It's the moral equivalent of Mobil Speedpass, although then you'd also need different cards for every other retailer brand you're likely to visit as well, juggling a fistful of creds for Shell, Sunoco, BP, Gulf, Chevron, etc.  Another obvious downside is that the network always knows who charged where.  We don't get the somewhat anonymous equivalent of pulling into a random gas station and paying cash for the energy intake.  Some chargers also have credit-card readers, which *should* all be EMV chip-enabled by now, but they don't always work and aren't anonymous either. 

Leaf charging on CHAdeMO Leaf was almost finished
The Leaf was using the CHAdeMO plug, because that's what Nissan decided to stick with for now.  One downside with CHAdeMO is that the car needs two different connectors, and thus a large charge-port door to cover it all.  Here's a better view of the two different inlets.  There seems to be some fairly nice gasketing around the essential parts to seal them away from water and snow, a particular concern for a car with its charge port right on the *front*.  The Kona has the same problem, and some owners have come up with some creative foam-gasketing hacks to seal the port door a little better.

I could see that the Leaf was almost full, because cars and rapid-chargers exchange a lot of information about battery and power state and generally display it to the user.  Perhaps the Leaf's on-board telematics would also soon notify the owner's app that it was finished charging?  Good guess, or fortuitous timing -- I had just set up the scope on my hood and clipped its probe to the pilot tap, when the Leaf owner walked up and unplugged.  She was more interested in getting her groceries home than my technical setup, and just got in and drove away.  But now I was free to play.


  While this charger was gratis, I still had to "authorize" to it, and that of course depends on it having a working cellular-data connection to talk back to the home office.  Sometimes those mechanisms fail.  Sometimes other mechanisms fail, such as protocol errors preventing charger startup or flakey/misaligned plug connections.  No particularly useful information is shown to the user about what went wrong, but it behooves anyone that runs into problems to call the support number immediately and report any outages.  Sometimes the network operator can peek into the charger's log and see what the actual problem was, and open a repair ticket if needed.  Sometimes they're just clueless, and spend the whole time "apologizing for the inconvenience" but not able to fix anything.  And sometimes we can't even reach their call centers because their whole phone system is down.

If this sort of crap happened to the trucking industry, we'd all starve.

This is why charging network operators have to start thinking more like providers of "critical infrastructure", because if someone is stranded at a broken charger without enough energy to drive to another one, now you're talking potential life-safety issues or major inconvenience.  Planning ahead and accounting for external conditions like weather obviously helps for a trouble-free driving experience, but things don't always work out as intended.  As long as density of chargers remains so vanishingly below that of fuel stations while sales and adoption of electric vehicles grows, it really is kind of a critical-resource situation.

I mention all this from a viewpoint of relatively little public fast-charging done myself, and this session at the Chargepoint was going to be my very first time trying it.  But there are plenty of videos and horror-stories about roadtrips delayed or rerouted due to non-functional equipment, all of which lends perspective and helps set expectations, howver non-glorious those may have to be.

Did I mention "work in progress" yet?


Pilot line at 5% with PLC superimposed Fortunately, everything was functioning for my first go here.  I plugged the big klunky head into the port as the charger display said to do first, and had a look at the scope.

The rest of this gets super-geeky, [like it isn't already??] and a bit of external reading on CCS and the Open Charge Point Protocol would help in understanding what we see here -- and more importantly, what we don't see here.  Once the charger realized the car was plugged in, it emitted a pilot-line duty cycle of about 5%, which means "digital protocol required".  Already I could see little packet envelopes on top of this signal, at a lower amplitude of 3 or 4 volts peak-to-peak.  The car wasn't charging yet; I still had to do more steps.


CCS plugged in I beeped the RFID card, hit the charger's "start" button, and listened intently.  The usual clicking and clunking of relays happened, this time adding the big DC contactor in the junction box of the car, the port's LED ring turned green, and it was off to the races.

PLC long packet From then on it was all about miniscule data packets, exchanging status and control data.  I spent the next while examining these little bursts, messing with trigger levels and timebase to try and get some decent screenshots.  Here's one of the typical longer packets, which we can't really analyze any content of, but visually, it clearly has some sort of preamble and then a payload.

PLC short packet Here's a shorter packet -- perhaps a quick ACK of something that went by before.  The big open pulse at the right is the pilot signal, flying way off the top since I've got the gain up.  The timeframe is quite short here; remember that the pilot spike is five percent of a 1 KHz square wave.

Expanded PLC preamble Expanding the preamble or any other part of the packet doesn't tell us much; it's kind of a random radio-frequency mishmash running at several megahertz.  PLC is basically a modem, with similar scrambling and modulation schemes as modems used on cable systems or phone lines [anybody remember those by now?].  Several OFDM carrier frequencies are dynamically assigned based on end-to-end conditions, so to get anything meaningful out of this you'd need a PLC and ISO 15118 analyzer to demodulate and sort out the transmissions.  It is kind of interesting that the patterns here are regular at all, but it may be part of how PLC syncs up.

PLC marching right over pilot squarewave The communication is not synchronized with the pilot waveform at all; either end sends when it feels like, and the superimposed waveform can march right over the pilot squarewave and probably still be received just fine.  Besides, the protocols above this allow for plenty of retry and error correction.

OSI stack for OCPP That's where we get even more alphabet soup: OCPP is actually a full OSI network stack, with dynamic IP [v6?] addressing and then TCP carrying some kind of enhanced XML between the car and the EVSE.  All over the pilot line, as a one-wire transport network.  Dubious smart-grid needs aside, this kind of encapsulation overhead is what happens when you let millennial "google kids" design network protocols.  They don't know any other way, and without their bloated web-kit type development libraries they'd be completely floundering as to how to do this.  The only developers who appreciate compact and efficient data transmission anymore might be the folks working on the CANbus side of things, still an area where small bit-fields carry a lot of meaning and speed is of prime importance.

All the ways that DCFC can fail Atop all of that are many steps for the car and the charger to sync up and detect errors in the process, and here is Hyundai's litany of the reasons it can fail.  Note the line with the shortest timeout near the bottom -- a "demand request" is interactive charge current regulation, and must be acknowledged and honored within half a second.  We don't want to be blowing up batteries, after all.  If a charger completely wigged out and stopped responding to requests to regulate or drop current, the car has the ultimate emergency option of opening its own DC relays.  Risking that under high current load may arc-flash and damage the contacts, so it's not something we want to have happen unless absolutely needed.  Relay contacts can weld closed if they're abused, so additional checks for that are done before and after charging finishes.  Normally it's up to the control electronics to bring current safely to zero before messing with any of the electrical path.

  That little CCM box under the car's dash handles all of this on the car side.  Its physical design and inconsistent representation in the service data makes me think the whole fast-charging capability was done for the Kona as sort of an add-on late in the design, almost an afterthought, and with some indecision whether to mount the controller underhood or inside the cabin.  What also supports this idea is that my New Hampshire buddy's Bolt from around the same manufacture time does not have fast-charging at all -- just a generic J1772 level 2 plug in the side, and a space where the big DC contacts could have been.  In that year of Bolt, it was a model *option*, which needed quite a few more parts added to the vehicle.  The guys at Weber State describe it rather thoroughly, starting around 11:00 in this video.  If a Kona without fast-charging existed, the big relay box hung off the side of the charger would almost be redundant.  The battery connection could go straight into the inverter, and the two extra orange DC cables out to the charging port wouldn't be needed either.  After that, the only real difference is the code running in various modules that would either support fast-charging or not.

One downside of the overall V2G concept is that it can fundamentally put a vehicle on the open internet while it's plugged in.  The security aspects of this have been talked about but not really worked out yet, and the more complex the protocols become the less likely real security will be inherently baked in and NONE of it is likely to be under the end user's control.  I already worked hard enough to take my own car OFF the internet; now every time I fast-charge it could be back on??  Hopefully the data exchanged by the CCM is *only* directly relevant to charging, but as these protocols develop I could easily see it leading to a more generalized victimization of owners.  Cell data down?  Oh hey, here's this other kind of Internet connection, allowing the Kona to phone home to Hyundai/Kia anyway and get a wad of unsolicited firmware updates stuffed down its throat.  With the thought processes or lack thereof that often get put into these things, that's a frighteningly possible scenario -- just from an innocent attempt to add some range.


Pulling 44 kW on the Chargepoint Chargepoint shows same power
The charge had ramped up to a healthy level, albeit not right to the full 50 kilowatt rating of the box, and the displays in the car and on the charger were matching reasonably well.  It peaked around 46.  That seems to be the usual scenario, although it was unclear which side was doing the down-regulation at that point.  Since the Kona is rated at something like 75 kW maximum, it was probably the charger not wanting to go at its flat-out maximum.  45-ish kilowatts is still enough power to run a good-sized rock show with a lot of lighting, but all I could hear was distant passing traffic and a relatively quiet fan in the Chargepoint housing.  Come to think about it, the other four or five kilowatts was probably in the warm air I could feel coming out its vents in the back, still only about 10% efficiency loss from its internal regulating electronics.

Now it was a question of waiting, although for this first test I wasn't going to go all the way to the 80% set-point anyway since I was only 20-ish miles from home.  I just wanted to watch it all work.


Chargepoint scope geek-out EVGo scope geek-out
The description and scope-shots here were actually assembled from two test charging sessions: the first at the Chargpoint, and another one a week or two later at an EVgo station in a local mall after my card for *their* network had arrived.  The second shot is at the EVgo setup; I had taken a nice long hike in a forest I hadn't been to before that afternoon, and stopped here on the way home, so my entire day was a voyage of discovery.  Just like back in the Prius days, here I was taking the o-scope out cruisin' on a Saturday night again and geeking out hard on car electronics.  A few people going in and out of the mall were curious about what I was up to, because usually when someone is charging a car it's all closed up and the driver is nowhere to be seen.  Instead, they saw the car with everything flung open, data packets flashing by on the scope screen, and a weird barefoot guy bouncing back and forth checking all kinds of numbers.  Perhaps this was a glimpse for them into the incredible layers of complexity that would become part of their own automotive future, even if they'd ultimately take it all for granted.

Charger faulted from J1772 latch open The physical charge port behaves a little differently on fast-charging, which is in the spec for how it's supposed to work.  On normal level-2 charging, one can hit the "unlock" button on the door handle or the key-fob and the charge port's latch lock will release.  Charging continues normally, and if nothing else happens, the latch lock will re-engage after 30 seconds or so.  Releasing the lock allows the user to press the latch button [which stops charging immediately] and pull the J-plug out.  But in fast-charging, the latch remains locked regardless, and the spec is that either end can put a stop to charging only via network protocol, and monitor all the network safety-dance to make sure things shut down properly.  For that purpose, fast-chargers have start and stop buttons.
On the first Chargepoint trip I decided to play with this a bit, and see if the primitive "proximity" circuit in the latch would have the desired effect instead.  I pulled the orange "magic mushroom" under the hood to manually release the lock, and then clicked open the latch button and held it for a moment.  More klunking happened, and charging stopped as I expected.  But had I just arc-faulted my big DC relay??  No way to really tell, but the charger had clearly seen that something had gone awry.  Here it was making sad puppy-eyes at me, and the display was scrolling "ERROR 50".  I was done with the experiment anyway, and put the CCS plug back in its holder and my gear away.  It took another couple of minutes for the charger to get out of this state and reset, but it eventually did on its own, so I headed off.

Auto-reduction of charge power near limit On the second trip, I let the EVgo session charge higher than I'd done at the Chargepoint.  [Note the odometer difference at the bottom of the display; there was some distance and regular home-charging between the two tests.]  Despite the Kona's maximum DC charge rating, it starts asking to ramp the current down around 70% battery regardless of source capacity.  The usual suggested fast-charging target is 80% rather than 100 for most vehicles, the theory being to keep the battery packs in a safe region under the very high currents they're receiving and not unduly stress the cells by pushing them hard so close to their upper voltage limit.  It's not a complete cutoff -- one can still creep slowly up to full at one of these stations with enough waiting, but it's not worthwhile, especially when networks insist on billing by *time* rather than *energy* actually delivered.  Practically, it further limits how far a driver can reasonably go between chargers, not to mention ratcheting up the cost for simply wanting more safety margin.
 
  Because of the variability of vehicle charge rates, billing based on time is flat-out gouging, a denial of physical reality, and has to change, as soon as possible.  The excuse for it originates from the fundamentally mistaken notion in several states that providers of electric car charging are trying to be public utilities, and are thus prohibited from reselling energy without state regulation and all kinds of permits and special status.  This is wrong, since the energy is for a specific purpose and not being re-sold as a generalized service.  It's a well-known problem, but as of late 2019 only about half the states had clued into the truth and clarified their laws and regulatory guidelines.  In the meantime, many of the charging networks had adopted the paranoid and profiteering approach of billing by time, but they've screwed it up in the process.  The Kona itself, in fact, is one of the vehicles at the center of a raging controversy over taking a "tiered" approach to billing, where more is charged per minute for higher power levels.  The problem is that on initial negotiation, CCS reports what the car is *capable* of accepting, and then the running reality of power level is usually quite a bit lower but the "tier" pricing doesn't adapt to that.

If you went to the deli for a half-pound of tuna salad and they happened to be out of half-pound containers that day, how would you feel if they handed you your half-pound of food but charged you for a full pound simply because the container *could* hold up to a pound?  How would you then feel if the deli owner got defensive about it when called on such bullshit dishonesty?


  On the road for real

I felt the pain of this more sharply when I took the Kona on its first real roadtrip, from Boston to the Philadelphia area for a convention.  One motivation to go was that there was a rapid-charger *on* the property of the convention hotel, so I figured getting ready for the trip back would be that much easier.  But I had to charge elsewhere along the way too, and the viable options basically boiled down to EVgo and Electrify America.  At least I could plan where to stop and some backup strategy well in advance, using Plugshare and OpenStreetmap and the networks' own websites, so while I knew it would cost a bit and take a little longer I was ready for it.

What I had yet to fully internalize was that a lot of charger installations are in relatively out-of-the-way places, like the desolate far end of mall parking lots, with sketchy lighting, dubious restroom availability, a long walk to any local resources, and no attendants around.  Quite a different feeling from a well-populated travel plaza with a warm 24x7 convenience store right there and *coffee*.  Waiting around for a charge and staring at a line of cold, closed storefronts or the cage where the dumpsters are kept is not exactly the most comfortable experience.  Wouldn't it have made far more sense to put chargers in along the curbs of popular truck stops along the interstates instead, where people are already used to heading for their travel needs?

80% suggestion icon on Kona dash display Ignoring the charge-level advice farther above, I had set the car's limit for DC charging up to 90%, thinking I'd have a little more "insurance" for making the next intended charge spot.  And the display popped up something I hadn't seen before -- a little flag pointing to the suggested 80% level, with a clearly shorter time to get there.  It seemed to be nothing more than a bit of advice, but it was interesting that the *car* had been given a strong notion that fast-charging really only should go that high.  And from this charger, an EVgo station somewhere near the Tappan Zee, I was only getting 42 kW instead of the 46 I expected, making the session even less cost-effective.  And because of the stupid way EVgo's accounting was set up, the session cut off after 45 minutes anyway and I never even reached that 80%.  It gave me enough to make the rest of the trip to Philly, though, so I kept rolling.

Electrify America charger power supply On the way back home I decided to try Electrify America for the first time.  This is the network spun off from Volkswagen group after the Dieselgate flap, with about $2B allocated to fund their atonement in the US -- a big public EV charging buildout.  They were also pursuing big plans in vehicles on all fronts -- the Audi e-Tron was already out and the Porsche Taycan was just hitting the market, with the VW "ID" microbus-allke in the wings.

There were four or five charging heads here, connected back to a common power box.  They were supposedly 50 kW, but I couldn't tell from the specification label on the box as the supply is probably shared across all the stations.  In setups like that, more vehicles connected at once often receive less power each as they have to share the maximum load.  Even Tesla does that, but only splits between two heads at a time.

 
  I hadn't bothered ordering an EA tap-card because I knew that all of their stations had a credit-card reader on the front, and this group had proper chip slots so a card-only transaction would have a *little* more security wrapped around it.  Chargers in out-of-the-way locations would obviously be targets for card skimmers, maybe even easier than gas pumps, but that's one of the things the EMV smartcards are supposed to help secure against.  The first head I pulled up to didn't work; it read my card but couldn't negotiate charging startup for some reason, and at least assured me that I hadn't been billed.  I moved over a stall, and that one seemed okay and started up.  To fill time I called the bum charger in to EA support, went to find the loo at a nearby McDonald's, and then came back and talked with a guy who happened by and seemed generally interested in electric vehicles.  He wandered off, and I grabbed a snack and continued to monitor charge progress.

Overpriced charge session completion EA doesn't arbitrarily limit session times, so since I still had over 200 miles to home I let the charge go a little over the recommended 80%.  It had become slow by then; with diminishing returns and the stupid per-minute meter still ticking.  I wasn't at the really "controversial" tier because this was only a 50 kW unit, but again, I never got more than about 42 kW out of it.  Even if I had cut off sooner, this was still rather expensive energy cost -- 37 cents per kWh, 9 cents a mile, or about the equivalent of driving a 30 MPG gas car.

And that didn't even get me all the way home.  I had to find another waypoint about 40 miles out to make sure I'd make it; conveniently, another Hannaford's/Chargepoint deployment.  Which I stopped in the proper way this time after imprisoning sufficient electrons, because sitting around in a desolate mall on a Sunday night in the cold is pretty boring.  After finally getting home, I ranted about the experience into an appropriate forum.

At this point, electric vehicles used under the same fueling model as going to petrol stations provide about zero financial advantage and take a lot more of one's time to deal with.  Roadtrippers and people who can't charge at home, who depend on public infrastructure, are totally getting taken for a ride.  That's not exactly the way to help promote EV adoption in those markets.  It's hard to believe that charging network operators can't or won't do the same simple math.  Well, maybe it's not so hard...  Electrify America, for example, exists *because* of corporate greed that got caught out, and it wouldn't surprise me if everyone working there feels some resentment about that and less inclined to personally engage and truly support what they're doing.  It might seem like the equivalent of forced community service in a way, but they certainly earned it.  Big corporations like VW that have proven themselves *capable* of that kind of arrogant and secretive disregard of people and the environment for the sake of money, still can't be trusted to do what's best for the public long-term.  As long as they can get away with underhanded practice and focus on profit uber alles, there will never be any true transparency or fairness.

What I could dream about seeing is a change to those enormous signs along the interstate, which seem to have standardized on showing the gasoline price in red and the diesel price in green.  How about adding a cents-per-kilowatt-hour price in a nice bright blue, to draw customers in to that generous line of fast-chargers opposite the fuel island that already has *twenty* gas pumps??  Blue is already sort of a pseudo-standard in EVSE hardware to indicate "charging", so it would fit right into an updated model, assuming that green ironically remains taken to indicate the dirtiest fuel.  First, we need to set the public expectation that anything seen in blue *would* be a price per energy unit just like the other numbers, not some cocked-up guesswork about time.

It'll be interesting to see how all this eventually settles down.


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