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The Throughput Problem: Recharging Electric Cars Requires the Patience of Job, And now you have to wait in line for a 30-minute long partial refueling!

CAR GUY - The Throughput Problem: Recharging Electric Cars Requires the Patience of Job, And now you have to wait in line for a 30-minute long partial refueling!   By Eric Peters, December 5, 2019, 12:04 AM

There was an interesting story over the holiday about electric cars piled up at “fast” chargers … waiting in line for other EVs to finish “fast” charging. This brings up the problem of throughput — another of many EV problems not being reported by the general press or the car press (the latter being inexcusable).

It is a function of the EV’s much longer recharge time versus a non-electric car’s time to refuel. Even in a best-case scenario — at what are hilariously (and depressingly) styled “fast” chargers — an EV takes at least five times as long (about 30 minutes) to recover a partial charge as it takes to fully refuel a non-electric car.

Consider what this means in terms of how many electric cars can recharge in one hour at a limited number of “pumps.”

A gas station that has, say, six gas pumps can refuel six cars in about five minutes, but for the sake of discussion call it 10 minutes each — to take into account people leaving their car at the pump for a couple of minutes longer than it takes to fill up to go inside to buy a soda, et cetera. The station’s throughput at that rate is six cars every 10 minutes. Twelve cars in 20; 36 cars in an hour.

But six EV “fast” chargers can only charge six cars — partially — in 30 minutes. In the same hour that it takes to refuel 36 cars, only 12 EVs are partially recharged — this being necessary at a “fast” charger to avoid damaging the very expensive battery and shortening its already short useful life. The EV can only accept about 80 percent “fast” charge; the remainder has to be charged slowly. Well, even more slowly. The full charge takes an hour-plus — but let’s leave that problem aside for purposes of this discussion.

The EV leaves the “fast” charger with 80-percent charge.  Which means it’ll have to be recharged again, sooner.  That’s the best-case scenario, remember.

The only way to mitigate this — in terms of the number of EVs that can charge at the same time — would be to build at least three times as many “fast” chargers as there are gas pumps. But where will the money come from? And where will the space come from?

Six pumps fit easily on a small concrete pad. But it would take the equivalent of three times as much space to match the gas station’s throughput capacity with EV “fast” chargers. This means a tripling of real estate and construction costs to the owner of the “fast” charge” station. More waste, too — of concrete and steel and all the other material that goes into building a gas — or EV — station.


Would the local power distribution system be ready for that?

Would the grid be ready for that?  Easier said than done…

Would the renewable energy converters be ready for that?


Bob Meinetz's picture
Bob Meinetz on Dec 7, 2019 1:53 am GMT

Noam, fortunately a lack of public charging will never be a significant obstacle to adoption of EVs.

I charge mine while I sleep. I don't have to wait for a charger, I don't even have to get out of my car. Because most other EV drivers are like me, transmission upgrades will be rarely be necessary - EVs are being charged when demand for other purposes is low.

Bringing up the importance of clean, nuclear energy - there's nothing that does baseload better.

Noam Mayraz's picture
Noam Mayraz on Dec 7, 2019 6:55 pm GMT

Bob, I grossly disagree with your statement "EVs are being charged when demand for other purposes is low."  So far I am aware that only California has different cost of electrical energy in every 24 hours period, others might have that incentive as well.

In the US of A people do what is easier for them to do - we fill up our fuel tank when it is low; we do not wait for the cost of fuel to drop.

Plug-in EV are plugged in when the drivers arrive at home, after dealing with the roads rush hours, just before the evening power consumption rush hours.

I suspect that no-one, but you, get out of bed at midnight and/or sleeps in the car (many homeless do that in California), to plug her / his EV.   

"I charge mine while I sleep. I don't have to wait for a charger, I don't even have to get out of my car."

Having stated the above, I am not surprised that all y'all (i) pollute God's Green Earth with batteries’ environmental unfriendly materials and (ii) burn unnecessary fossil energy to produce batteries, use (iii) transmission line losses, (iv) battery charging losses, (v) battery internal storage losses and to boot (vi) battery discharge losses – aka six (6) ways from Sunday. 

That is not considering that battery propelled car is heavier than a comparable size / performance car, therefore is using by far more energy to move that weight.  As you know, spare wheel is not included.

Are you by any chance an engineer or merely Greta Thunberg admirer???

Bob Meinetz's picture
Bob Meinetz on Dec 8, 2019 8:54 pm GMT

Noam, you're confusing several issues. First of all, I'm relating my personal experience, about which I can confidently claim I know more than you, or anyone else in the world.

Second, time-of-use pricing plays no role in when I charge my car. Though it's often in the late evening, electricity costs me ~4¢/mile, a fraction of what I'd spend on gasoline. It's my impression people living in the U.S. of A. like to save money.

Third: i) Driving EVs in California, across the board, including emissions from generation, results in fewer emissions than driving comparable internal-combustion cars powered by gasoline. Download Argonne National Laboratory's GREET model for Excel, and run some of your own simulations. I have, and it does, ii) Nearly 100% of lithium is recycled, so I have no knowledge of the horrible environmental impacts of batteries you describe, iii, iv, v, vi) All of these losses are included in the well-to-wheels, comprehensive GREET model.

I'm an admirer of Greta Thunberg's commitment to addressing climate change, if maybe not her suggestions on how to do it. I'm not an engineer, but trust the knowledgeable engineers at the Dept. of Energy, who spend every hour of every business day analyzing fuel and emissions pathways. I've met them, I've attended workshops at Argonne, and I can confidently say they're authorities on the subject.

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