Reply to post: Re: 350kW!!!!

700km on a single charge: Mercedes says it's in it for the long run


Re: 350kW!!!!

Actually, we both missed something here.

I agree that I mixed up peak power and average mileage, I got the numbers wrong. But your analysis is even more wrong.

Firstly, I said that 350kW charging was unacceptable, but anyway so was 30 kW. The article is based on a car that charges at 350kW but you casually down-scoped by a factor of 12.

“Overnight” is just not how plugging something into a socket works. Most people will typically arrive home roughly at clocking off time, synchronously, and plug in. At that time the full charging load kicks off for some length of time, even if it *theoretically could* be trickled overnight.

The *right* solution is probably to limit typical domestic charging to 10 kW (not even 30) then everything automatically trickle charges overnight. Fast charge can be allowed, but must be separately and heavily premium priced to prevent everyone doing it.

We actually agree on that side of the practical solution, you just chose to disagree for whatever reason.

Your idea that people will agree to use their car batteries as spinning reserve for the national grid voluntarily, is economic rubbish for several reasons:

1) The car battery lifetime depends on the number of charge/discharge cycles. Nobody is going to reduce the lifetime of their car to help out the grid, without both being paid a lot for it and having control over the process. And “paid” doesn’t mean per kWh, it’s paid for the capacity and capital depreciation. The grid would have to be prepared to pay every single car owner at least a thousand a year for the impact on their car. That’s paying £1000 to a customer who is only paying £500 annual total for their electricity..I don’t think the electricity company would stay in business long.....

2) Obviously, I can’t risk going empty when I want to drive, so any smart charger must limit the usage to say 10% of capacity. You actually do recognise above that this requires over-provisioning the car to compensate, to achieve the same effective range. So, you are just replacing efficiently concentrated industrial capacity, with capacity that is both inefficiently fragmented and *hauled every day on the roads*. That’s just crazy.

3) Recognising the idea as unworkable at scale, you just say “not overnight......there is time to build the extra capacity”. According to both the green lobby and car companies, the car transition should be largely complete by 2030. It would take a minimum of 20-30 years to even double our current grid capacity. So, no, there isn’t time even if we had started ten years ago.

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