Yeah this is one area where there's a lot of deceptive marketing. For example the Kia EV6 specs list a max fast charging rate of 350 kW but what that actually means is that you need a 350 kW charging station to reach the car's actual max charging speed of 240 kW (or 180 kW, depending on the battery options).

Granted, that is still nice and fast, and the EV6 is a great car, but it's really frustrating how hard it is to compare charge speed from different manufacturers.

Wow that is the scummiest thing

The car simply states the fastest DC connection it supports - 350kw. It works with any charger up to this wattage, just like my laptop charges from any USB-C source up to 100w - was I missold my laptop too because if I use a 50w charger it only charges at 50w?

DC Fast Charge Time (10-80% @ 350 kW via Electric Vehicle Supply Equipment) Level 3 Charger: Approx. 18 min.

and

Drive Battery Energy: 77.4 kWh

The battery is 77.4 kWh. This implies the battery is charging at 180kW.

If it were taking in the full 350kW and losing 170kW as heat that would be one (inefficient and dangerous) thing, but it doesn't sound like it actually draws 350kW?

For comparison, they say 73min for charging at 50kW, which implies the battery is charging at 45kW. If we figure that same 10% loss, then to charge at 180kW it's probably drawing 200kW from the charger.

[1] https://www.kia.com/us/en/ev6/specs

[2] 70% * 77.4 kWh * (60min / 1h) / 18 min = 181 kW

I'd thought they were advertising a 10% to 80% charge because that's the period over which they can charge at max speed? Looking now, it seems like they start tapering at 50%, and it's peak draw is 235kW? https://www.arenaev.com/kia_ev6_crowned_the_best_charging_ev...

(I agree this is very good, but it's still wrong to quote 350kW if they never draw this much.)

I assure you that my mother has no idea what a watt is.

> it's really frustrating how hard it is to compare charge speed from different manufacturers

Is the discrepancy just the inefficiency (i.e. waste heat) of the charging circuitry and/or battery chemistry? And if so, do different EV battery+charger systems have significantly different efficiencies?

I would have expected that the consumer-facing spec is always the power taken from the grid, that there is always some inefficiency (you can draw less energy from the batteries than came out of the grid), and that the level of efficiency would be roughly similar across all cars.

If that were the case, it wouldn't be much of a problem to compare charging rates across cars. But perhaps one or more of my expectations are wrong.

Oh, and EVs presumably vary wildly in their "fuel economy" (miles per kilowatt-hour or whatever unit EV folks use), so even a "fair" comparison of charging rate presumably wouldn't paint the entire picture.

I'm not positive on the specifics but I believe it has more to do with the combination of supported voltages/amperages offered by different chargers. i.e. a "350 kW capable" charger in practice means it can do 800V charging, which other chargers of lower kW ratings typically can't do, and the EV6 requires 800V to reach its max charge speed but can't actually handle a high enough amperage to get to 350 kW.

Like I said though, I might be confused on some of the details there, but I'm fairly positive it's not just waste heat...dissipating 110kW of waste heat would require some pretty insane cooling hardware.

Oh, and EVs presumably vary wildly in their "fuel economy" (miles per kilowatt-hour or whatever unit EV folks use), so even a "fair" comparison of charging rate presumably wouldn't paint the entire picture.

This is indeed a good point. A more relevant measure of charging speed would be something like "miles per hour at EPA rated efficiency", though even that gets messy since most cars don't charge at a linear speed. And I haven't seen any car manufacturers use this metric other than Tesla, who like to brag about their supercharger stations exceeding 1,000 MPH of charging speed (though only the newest stations can just barely do that, for very short durations, and only on certain car models). "Time from 20%-80% charge" would also be a better metric, due to non-linear charging speed curves, but I haven't seen that one used much either.

Pretty much the only time charging speed even matters is the "road trip" mode, where you are driving further than a single battery charge in one day and you want to stop as little as possible. In that mode, all I really want to know is what my duty cycle will be, e.g. "every 5 hours of driving you'll need to stop to charge for 30 minutes."

If I'm not in road trip mode, then as long as I can Level 2 charge overnight and/or all day at work, I would barely care what the peak charge rate is. It would still be nice to have something quick for the rare pickle (and of course road trips), but it doesn't seem like that big of a deal. I guess it's so prominent in marketing because range anxiety is still so deep in our mindset?

Counterintuitively, it can be cheaper timewise (and money-wise) to spec and build a new factory than to re-tool one that was custom-built to manufacture cars with a large set of core assumptions about power plant and drive train.

A trivial example (in unnecessary complexity, physical properties not really involved): on the German website, when you pretend to be ordering an Audi A6 you get twelve different sets of wheels to choose from at five price points. And that's before you add winter wheels to the mix. And tire options, and different approaches to the pressure gauge problem and theft preventing bolts. The Tesla S offers a choice between baseline and expensive an optional winter wheel. Now this isn't an example that directly relates to range, but it's organisational cruft. They need to have boatloads of people employed only for solving various aspects of their solution to the made-up problem of not enough wheel choice (all the way from design to spare parts logistics..) and that robs focus. Those people might actually have better careers than their peers dealing with batteries and they do compete for intraorganizational attention. It's all rooted in customer expectations built over decades of inventing car problems to solve better than the competition, after the ICE was basically done. New, BEV-specific lines can help (apparently the e-tron gets by with only eight sets of wheels at two price points, yay!), but they are far from being as much of a fresh start as that blank slate as Tesla has been.