General > General Technical Chat
EV-based road transportation is not viable
tggzzz:
--- Quote from: tszaboo on February 17, 2023, 01:48:27 pm ---
--- Quote from: tom66 on February 17, 2023, 10:25:41 am ---The Type2 connector, as used for virtually every EV today, is robust. You can run over it with a car and it will still work. The connectors have weatherproof covers which keep water and most detritus out of them. I've been using my home EV charger for almost 5 years now and there's no issue with the connectors on either end, and that gets cycled daily.
--- End quote ---
I've seen it blow up a Tesla's internal charger 2x (tesla didn't fix it with warranty, owners fault of course), tripping an entire office's circuit breaker. Probably contact resistance went up.
I know this is anecdotal.
--- End quote ---
Ouch!
Old engineering maxim directly relevant to this topic: "it is impossible to make something foolproof because fools are so damn ingenious".
Then malice has to be added to the equation. Then other "suboptimum" human behaviours found in the wild.
Tesla/Musk has a habit of denying there is any problem with their product. Today's example: https://www.bbc.com/news/technology-60230072 . Unfortunately there are too many others.
Fortunately there are more responsible manufacturers, e.g. VW which is apparently tipped to become a major supplier of BEVs. Let's hope they've learned lessons from "dieselgate", as Ford did from Pinto.
tom66:
--- Quote from: tszaboo on February 17, 2023, 01:48:27 pm ---I've seen it blow up a Tesla's internal charger 2x (tesla didn't fix it with warranty, owners fault of course), tripping an entire office's circuit breaker. Probably contact resistance went up.
I know this is anecdotal.
--- End quote ---
Eh? How would increased contact resistance 'blow up' the onboard charger? From the charger's perspective, all it sees is a lower supply voltage, and it acts as a constant current sink... so it's hard to see how that could really damage anything. Eventually it might trip the AFCI algorithm if the voltage at the charger input varies too much, but that should only suspend that charging session.
I suppose in the worst case if the socket temperature sensor failed *and* you had high resistance contacts you could melt the socket, requiring replacement of both socket and cable. However, I know at least on my car "socket temperature sensor implausible" is a fault code, which when set limits charging current to the minimum if it is active (a pain, but at least you can charge in an emergency, if not a bit slowly). I would be quite surprised if this is not common on all EVs. Tesla has done a lot to improve safety of charging, including the AFCI algorithm which was added as a safety feature after some people reported poor sockets arcing and burning contacts. The microcontroller in the charger observes the AC line voltage and backs the current off if it detects possible arcing.
PlainName:
--- Quote --- I would assume you go to the supermarket from time to time. Perfect place for chargers. In the time it takes you to pick up some groceries, you can add 100km or so to the tank. Etc etc.
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Our local large supermarket has four spaces with chargers. So let's assume they are quick on their feet and take only 15 mins to shop. That's 16 cars per hour or 284/day (but actually less, because some will turn up, not find a slot and go home without charging). I think there needs to be HUGE rollout at every supermarket for this to make a dent. Eventually that might happen, but if you're a current early adopter it's a future potential, not something to rely on this year or next.
--- Quote ---If you go to the office every day, those office will have charging points.
--- End quote ---
What, for every employee that has a car? Have you seen the size of some office car parks? It works now but the charging stations need to be at least level, if not a step ahead, of EV ownership.
Of course, not every EV will need to be charged at the office or shops since many can do it at home, but the massive lack of charge points I see doesn't encourage me to rely on away-from-home charging.
Ice-Tea:
--- Quote from: PlainName on February 17, 2023, 05:51:31 pm ---
--- Quote --- I would assume you go to the supermarket from time to time. Perfect place for chargers. In the time it takes you to pick up some groceries, you can add 100km or so to the tank. Etc etc.
--- End quote ---
Our local large supermarket has four spaces with chargers.
--- End quote ---
Thats not the point. The question is: how many parking spaces are there over there. That's your potential capacity.
--- Quote ---If you go to the office every day, those office will have charging points.
--- End quote ---
What, for every employee that has a car?
[/quote]
Not at all. Some will charge at home or elsewhere. But even then, let's assume they all have to charge at the office. With a range of 400km and most people driving less (or much less) than 100km a day, you would need 1/4 or less of your spaces electrified.
Is that a lot of work? Cost? Obviously. But I dont see why that would be insurmountable.
tom66:
--- Quote from: Ice-Tea on February 17, 2023, 07:03:30 pm ---Thats not the point. The question is: how many parking spaces are there over there. That's your potential capacity.
--- End quote ---
Exactly. Large scale charging infrastructure is already a thing. See this airport for instance.
If every charger at 7kW is operating simultaneously, it pulls 5MW from the grid. I presume there's some kind of load balancing to keep the grid connection from being really silly, although it's not impossible the car park does have a 5MW supply.
EVs already support dynamic load adaptation: if the PWM carrier changes during charging, the car must reduce its charge current within 10 seconds (in practice it's instantaneous, because it's a computer-controlled SMPS.)
BTW: Average car parking space costs about £15,000 to construct on a surface-level car park. A multistorey is about £50,000. So a £500 EV charger is peanuts in comparison.
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