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Comment by stetrain | Hacker News Reader

So the power meter dutifully ticks up the charge you have used while plugged in. Then what? How do you pay it? Do you have to go track down some person who may or may not be on duty to read the meter, hope they read it before you started, and pay them in quarters?

Cars are designed to use AC. That's how all current Level 2 chargers work. They are basically dumb outlets plus a contractor, GFCI, and optionally a payment terminal. But beyond a certain level (around 20kW) the size and cost of putting a larger AC to DC converter in the car is prohibitive.

At one point Tesla Superchargers were literally racks of the same AC to DC converters found in the car, but fed with 3-phase power, bussed together, and cooled all external to the car. There's no other way to implement a reliable 20-minute roadtrip charge.

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Oh come on, pay for use is a solved problem. Look at gas pumps. But if it's not feasible to have a big DC converter in every car then no luck

So an AC outlet with a built in meter and payment terminal, that simply provides AC power to the car with an onboard DC converter, already exists. That's what basically every Level 2 EV charger is today.

(Really it's an "EVSE" not a charger, it is doing no charging work)

They have a couple of extra safety features (like a contractor and GFCI) and include the cable (in North America, in countries with the Type 2 connector you bring your own cable).

These chargers go up to 19.2kW commonly in the US, although the charge rate can be limited by the installation (circuit size) or the car (onboard charger capacity).

A helpful video about what's inside an AC EV "charger":

https://www.youtube.com/watch?v=RMxB7zA-e4Y

Really the only difference with the fancier ones is they have a screen and payment terminal or NFC terminal for activating and paying. Like a gas pump, although most want you to use their app and membership to save (them) on credit card processing fees.

DC fast chargers are a whole different story, where the AC to DC conversion happens external to the car.

Gas pumps are larger transactions, so the credit card fees are less of a hit for the business. A level 2 AC charger is about $1 per hour of electricity, so you're taking huge credit card fees for shorter charges.

Most of the apps have some sort of balance that lets you make one $10 transaction and then spend it on a lot of smaller charge sessions.

That's an interesting wrinkle on what should be an otherwise tractable. Perhaps the government should subsidize the transaction fees in some way like they subsidize the oil companies.

You must be using an unusual definition of subsidy. Gasoline is heavily taxed just about everywhere.

Anyway shifting around the costs doesn't change the fact that paying ~30% in fees is very inefficient

There’s a solution right in the problem: mandate a single “balance card” that pays all EV chargers.

Not sure why that gets a downvote. We use this solution all over the place. From transit cards to gift cards you pay a single transaction fee to the credit card company so you can then pay 0 transaction fees on the tiny purchases.

It gets downvotes because people don't need stupid card for gas pumps either. They are using credit/debit cards.

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