After a year of EV ownership as an electrical engineer, here are some things I believe to be hard truths and guidelines that I hope charge point operators and vendors will take to heart.
Maintaining proper free-market incentives is paramount
People like cheap stuff, and people especially like free stuff. What people (what I) don’t like is making a many-year commitment to a purchasing decision only to have the unit economics of that decision change mid-cycle. The EV market, and especially the charging market, needs to be sustainable not only in the environmental sense but in the actual business sense as well. One of 398298 gas stations going bankrupt is no big deal for drivers. One of 3 charge point operators falling into awful disrepair because they can’t afford maintenance is an existential threat to the whole industry. $0.60/kWh with 99.99% reliability beats $0.00/kWh with a dice roll that you need a tow.
Similarly, free charging incentives, particularly unlimited free charging incentives, need to die. The only thing worse than a tragedy of the commons is a tragedy of the commons at a nascent stage when the deployed infrastructure is operating perilously close to saturation and will be for the foreseeable future. Unlimited free charging means worst-case load on a system that’s already incapable of moderate load. Unlimited free charging means cars that could be plugged in at home clogging stalls for an extra hour per charge because the extra 20% now beats a second trip later. DCFC SHOULD accommodate drivers who can’t charge at home and who must use public charging capacity. Shifting drivers from $0.25/kWh charging overnight to $0.60 charging at rush hour is not that – it’s tantamount to kneecapping the whole industry.
Owners who bought into free charging plans should be offered a prorated buyout option, and I will gladly pay for it with increased DCFC fees in turn for a network I can actually use.
Idled converter capacity is unacceptable.
I own an EV6, which charges at 240kW peak. 50kW charging is very sad and painful to me. And yet, the worst thing I experience on a regular basis is that one Bolt (55kW max charge power) plugged into a 350kW stall with dedicated capacity (i.e. Electrify America’s status quo) can effectively offline SIX MORE BOLTS’ worth of charge capacity for the two hours a full charge takes. I could charge for half that time at even 50kW and get back to my road trip, rather than waiting an hour or more before I can even START charging. This brings us to our next point, shared capacity beats dedicated capacity.
Shared capacity beats dedicated, every time.
A 350kW charger is mostly idle even if a Hummer EV, the only car capable of sinking 350kW, connects. This is a basic physical fact of lithium ion batteries: they don’t charge at peak power throughout the whole cycle. Take the EV6: the 10-80 charge time is reliably 18min at favorable temperatures, which corresponds to 180kW average power consumed over the duration of that optimal-speed regime. In other words, the car peaks at 240kW (30% idle capacity) and averages 180kW (49% idle capacity). In other-other words, one EV6 connected to a 350kW stall charges in about 18min, where two EV6’s connected to the same stall would simultaneously charge in about 25 minutes, OR, with somewhat lucky timing, one could charge in 18min and the other in 18min with a 6-7minute delay compared to the first.
The point here is that more dispensers capable of on-demand converter marshalling from the same resource pool can get more cars through the station faster than dedicated-capacity dispensers, at on-average negligible impact to user experience.
Tesla’s V3 supercharger architecture gets this super right: 5 dispensers share 500kW of converter capacity, 500kWh (variable? I think?) of onsite battery storage, and 350kW of mains transformer capacity. The net impact is that any car can show up to any stall in the bank and typically get full charging performance, and absolute worst-case scenario, 5 simultaneously-arriving low-SOC cars can still get 70kW each. In a cars-waiting-in-line scenario, zero capex is wasted.
Idle fees help everyone.
Tesla gets this right: if nobody’s actually waiting, don’t charge idle fees, or discount them. If the station is busy, CHARGE THROUGH THE NOSE and get idle cars out of there ASAP. The worst charging experience is not showing up to an offline site – it’s showing up to a site with every working stall occupied and no drivers to be found. There’s a certainty in being unable to charge. Humans are more comfortable with certainty, even when it’s bad news. Humans are not comfortable with the uncertainty of a stall that MIGHT be available in 5 minutes, or MIGHT be available in 5 hours.
For charge point operators, this should be a no brainer. Make your customers happy, and milk that juicy zero-cost profit. A dollar per minute for no power delivered is way better margin than $2/minute earnings for raw costs potentially even exceeding that.
More dispensers in one spot beats more stations scattered around.
Obviously this has a limit: 17,000 supercharger stalls in one massive lot in Seneca, Kansas would be completely useless. But given the choice between four stalls here and four more 3 miles down the road vs 8 stalls here, I’d pick 8 in one spot every time. The core driving factor is that drivers have ~0% situational awareness of charger availability when they’re deciding where to stop, vs ~100% awareness once they arrive at a site. There’s huge room for improvement here in other ways, but concentrating chargers reduces the overall usability impact of minor failures like a broken stall or an idle vehicle. A broken stall at an 8 charger site means 12.5% reduced capacity, vs at a 4 charger site means 25% reduced. 5 cars waiting in line for 6 working chargers gets everyone on the road much faster than 0 cars waiting in line for 4 working chargers here, and 5 cars waiting in line for 2 working chargers there. Those 5 cars waiting for 2 chargers can’t make an informed decision to try another site when they’re unable to observe the live conditions miles away and minutes into the future, never mind whether they have the range to do it.
This holds doubly true on highways: 99% likelihood of charge success at a single site in-range beats the pants off of 50% likelihood of success at one site in-range, and 50% likelihood of success at another site possibly too far away to get to.
Special cases are to be avoided at all costs.
I’ll lead with the arguably unavoidable counterpoint of CHAdeMO. It does seem like unreasonable capex to equip every stall with a sunsetting, end-of-life charge standard. On the other hand, when only one stall at a site can charge your car, you’re guaranteed to wait in line even when there’s decent idle capacity. For eons, diesel drivers have been annoyed at the gasoline drivers who use the one diesel pump at the station. Experience shows it’s completely unreasonable to expect end-users to reliably accommodate “special interest” users. CCS drivers will use the one CHAdeMO charger at a 4 stall site with only slightly less than 25% likelihood. Chevy Bolts will use the 350kW stall over the 150kW stall 9 times out of 10 because “more is better.” Hell, I seek out the 350 stall deliberately and STILL frequently get it wrong. Merely remembering which side of the car your port is on frequently enough trips people up at gas stations, never mind when station design makes certain charger>car geometries impossible to connect. Every car should be able to charge with reliable and predictable performance at every dispenser, and any exception should be EXCEPTIONALLY well-reasoned.
These aren’t really discrete truths I believe in, but more along the lines of “things chargepoint operators should probably be doing more than they are” and other observations about the current charging experience.
Pull-through charging. There are EV pickups now, and they’re good. Maybe CPOs are waiting on the cybertruck to kick them in the pants, but if that vehicle never drops, there are already people towing boats and horses across state lines with rivians and Lightnings and they need to charge. Both vehicles very sensibly put the ports up front, but leaving a trailer blocking the whole parking lot isn’t exactly a valid status quo.
Related, Queueing. Pull-through stalls could help address this problem, but SOMETHING needs to. Capital is expensive, especially now, and maybe EV drivers will just have to resign ourselves to lines at charging stations. But lines only work when there’s somewhere to line up. Right now, charging at a full station is free-for-all chaos. Stations need to be designed assuming there will be times they’re full, and designed so that drivers trying to behave in good faith know how to do so.
Driver feedback. Drivers need to understand what’s happening. Is the station underperforming because the charge lead is hot? Should they use the other one that wasn’t just soaking in direct sunlight for hours? Is the car’s battery too cold? Is it too hot? Is the charger attached to a few broken converter modules? When stations fail or underperform, there are VERY often troubleshooting strategies a driver can attempt to get at least SOME charge. Until reliability is bulletproof, we should at least guide end users on what they might be able to try short of calling a tow truck. This one shouldn’t be necessary, see “shared capacity” points above, but tell drivers of slow-charging cars to avoid the fast-charging stalls, right on the screen, and right in the app.