250kW Superchargers vs 350/400kW fast chargers

[jgwozdzicki]

Evening all,

I see Ecotricity have announced they will be rolling out their own 350kw fast chargers on the electric highway as of next spring. Wonder when/if Tesla will be enable charging at those speeds. I know they have mentioned rolling out superchargers rated that high but no EV's to date apart from the Porsche Mission E can take that kind of charge. There was also an interesting article on Electreks site listing the pro's and cons. It can be found here.

Just wondered what people's thoughts were on the subject?

 

[nwdiver]

Just wondered what people's thoughts were on the subject?

It's not how fast you charge but how well you charge fast

Seriously though... what's the point of having a ~350kW charger if you can only sustain that level of charge for a few minutes? Yay, I got ~15kWh in 3 minutes but now I need to wait another ~30 minutes to reach 80% because it's tapered to 60kW... what was the point?

The battery is much more of a limiting factor than the charger. I'd be far happier with a car that can sustain a 100kW charge rate for 40 minutes than the ability to absorb >300kW for a few minutes...

 

[GeorgeSymonds]

None of the current cars will be able to use it, they already struggle to use the peak charge rate a super charger can deliver. As I understand it, those chargers are also Chademo and so you'd be using a dongle thing

 

[kbM3]

It's not how fast you charge but how well you charge fast

Seriously though... what's the point of having a ~350kW charger if you can only sustain that level of charge for a few minutes? Yay, I got ~15kWh in 3 minutes but now I need to wait another ~30 minutes to reach 80% because it's tapered to 60kW... what was the point?

The battery is much more of a limiting factor than the charger. I'd be far happier with a car that can sustain a 100kW charge rate for 40 minutes than the ability to absorb >300kW for a few minutes...

Mission E claims 15 minutes to 80%.

 

[nwdiver]

Mission E claims 15 minutes to 80%.

I'll believe it when I see it... I suspect there are a dozen or so ' * ' with that claim...

 

[arg]

The practical value of these "350kW" chargers is that they will charge several cars at once. The fact that they could charge a single car at 350kW if you had a suitable car at a suitable SoC is immaterial - apart from marketing where it sounds so much better than Superchargers despite being equivalent for practical purposes.

 

[SSedan]

They going to have liquid cooled cables and charging plugs? Then what about the in car stuff. Charging cables already get warm, you think the extra current is going to have a cooling effect?

Ever supercharge your car on an 85f day? Does it sound like the AC is barely running and has a LOT of additional cooling capacity? You think the cables from the port to the battery don't get warm?

Point is stop and THINK, OBSERVE a little bit. That kind of charge rate is not possible to support for any amount of time on current hardware, so a software update wont be able to help a lot. I kind of wonder if the most effective software solution for a margin gain might be to moderately prechill the battery to the lowest temp it can still take the current 120kw, when NAV is bringing you to the supercharger though that wont help in all conditions, like if the battery is already cold or if it is cold enough out that cooling is easy.

I think arg makes very good points too.

 

[VT_EE]

I'll believe it when I see it... I suspect there are a dozen or so ' * ' with that claim...

I agree, and am highly skeptical unless they are going to offer a 200KWh 800V battery.

 

[jgwozdzicki]

They going to have liquid cooled cables and charging plugs? Then what about the in car stuff. Charging cables already get warm, you think the extra current is going to have a cooling effect?

Ever supercharge your car on an 85f day? Does it sound like the AC is barely running and has a LOT of additional cooling capacity? You think the cables from the port to the battery don't get warm?

Point is stop and THINK, OBSERVE a little bit. That kind of charge rate is not possible to support for any amount of time on current hardware, so a software update wont be able to help a lot. I kind of wonder if the most effective software solution for a margin gain might be to moderately prechill the battery to the lowest temp it can still take the current 120kw, when NAV is bringing you to the supercharger though that wont help in all conditions, like if the battery is already cold or if it is cold enough out that cooling is easy.

I think arg makes very good points too.

Well this is what I'm struggling to get my head around. Pumping that much juice down a cable into a battery is going to generate a hell of a lot of heat at 350kW and Elon has already said there's no plan to increase the MS/X packs bigger than 100kWh so I can't see the benefit. I know the Tesla CHAdeMo adaptor already throttles due to heat on 50kW.

Arg does make a good point too. It would make a lot more sense at superchargers if both cars could charge at maximum without one getting preference over another.

 

[nwdiver]

Well this is what I'm struggling to get my head around.

Higher Voltage. The Mission E is supposed to have a 800v pack. Doubling the voltage can double the power without increasing the amount of heat generated. I still don't think the pack will be able to accept ~350kW unless it's a 200kWh pack like Alpine mentioned.

Power doesn't generate heat... current does. Power = Voltage x Current.

 

[jgwozdzicki]

Higher Voltage. The Mission E is supposed to have a 800v pack.

I know the higher voltage alleviates the heat issue to some degree but didn't know the Mission E had such a high voltage pack! Don't think there is anything currently that high on the market, I think even the new I-Pace is a 450v pack.

 

[docherf]

Higher Voltage. The Mission E is supposed to have a 800v pack. Doubling the voltage can double the power without increasing the amount of heat generated. I still don't think the pack will be able to accept ~350kW unless it's a 200kWh pack like Alpine mentioned.

Power doesn't generate heat... current does. Power = Voltage x Current.

I might be making a mistake, but if the Mission E had a 200 kWh pack, & claims it can charge 80 percent in 15 minutes, that's 160 kWh delivered in 15 minutes! Or a rate of 640 kW/h. At 800V, it'd also be running at 800 amps.
Did I screw that math up somewhere?

I hope they can do it.

 

[WannabeOwner]

Wonder when/if Tesla will be enable charging at those speeds

I think Tesla have pitched this 100% spot-on. (And the rest of the 3rd party providers, to date, have got it 100% wrong, by comparison.)

I don't think we need Superchargers that are 2x as fast I agree with @arg that not having reduced charge rate when "paired" would be a benefit, and if stalls are only occupied for 50% less time, that would improve throughput too. Provided no-one is slow-charging above 80% ...

I charge away from home 3 -4 times a month, 90% of that is at a Supercharger. Most of those times I am getting "just enough to complete my journey", so 10-15 minutes. By the time I've walked to the services building, had a pee and got a coffee, the car is ready. I struggle to fuel an ICE in 10 minutes (allowing for stand-and-pump and then queue-to-pay, let alone pee and buy-coffee ...)

Cutting charging time in half, for that use-case, gains me nothing. I suppose I would sit-in-car for 5 minutes, and not waste my money on a coffee (yeah, and a chocolate bar ... but I'll not have had the exercise either )

And will the 3rd-party chargers just be "Plug in, and walk away" like Tesla is? I know the only route, from current state, is "improvement", but every public charger I have used to date has been an horrific experience, compared to Tesla, and taht's assuming the single-stall is not occupied ... or broken.

A 300+-real-world-mile battery would have better benefit, for me, than much faster charging. That would change my Supercharging from 3-4 times per month to once per year.

This is UK forum, and for us Road trips are a rare animal, but they are a different thing, of course, but I doubt many people do that multiple times in a year. But even on those a 300+ mile battery, which would charge to 80% in 35 minutes, is still well over 3 hours driving between stops. When we have driven through France, in the past, we would swap drivers every couple of hours and just "press on"; for a solo-driver a stop every 2-3 hours is important, but I do agree that with EV (and two-drivers) the charging stop just prolongs the journey. But with 300+-mile battery the single, 35 minute, stop, on (what would be) a 540+ mile journey would not be burdensome, e.g. combined with a meal.

I'm really struggling to see how the Mission-E etc. 15-minute 80% charging scores a benefit, other than a fast-charger at a race track.

 

[arg]

A 300+-real-world-mile battery would have better benefit, for me, than much faster charging.

This is the real point. It is relatively easy to build a fast-charging battery BUT that means compromising other characteristics - weight, size, cost, longevity - all of which are important. Most new developments in battery technology can improve any of these properties: even if the new breakthrough only improves one of them, you can swap with the others by unwinding compromises you've already made.

Going to a larger battery size (built of the same cells) automatically gives faster charging in proportion - which is why Model S charges faster than other contemporary EVs. Indeed, at the time Model S was using a slower-charging (but more energy-dense) chemistry than the likes of Leaf etc. in order to get the right balance of range and charging rate. So we can expect a general increase in charging rates of mainstream vehicles as they move to 200-mile range capability.

It took me a while to realise just how finely tuned these compromises were in the original Model S. You can't easily just add more cells, as the extra weight then reduces the efficiency and performance so it becomes a case of diminishing returns (and it's already a heavy car). The range is just enough, the charging speed is just enough to let the charge-while-you-are-eating model make long trips acceptable. And it's expensive, but just about cheap enough to stand comparison with cars of the same price.

With advances in technology we can look for improvements in all these parameters, but given the huge need to improve cost and the related need to improve weight, it's not at all appropriate to 'spend' the improvements entirely on charging rate increase. So as far as passenger cars are concerned, we can really only expect incremental improvements on the charging rate currently supported by Tesla vehicles.

Hence the 150kW step in up CCS is genuinely useful for the 200-mile range generation of cars we hope are forthcoming for the mass market; Tesla's 120kW per vehicle is probably enough at the moment, but it's easy to see that extra 25% being useful at some point. And a car with 150kW CCS capability remains compatible with 50kW CCS.

The 350kW step in CCS on the other hand, while useful for things like buses with huge batteries, is hard to see as being useful for any ordinary car in the forseeable future. By going to 800V, it makes cars that can take 350kW CCS incompatible with existing 50kW CCS (without huge compromise in the design of the car to adapt the pack voltage).

It remains to be seen what Porsche have done on the Mission-E. The notional spec (80% in 20 minutes on a 95kWh pack) is only 230kW charge rate, so they've only obtained a modest benefit from going to 800V - it looks like pushing the technology for its own sake. Possibly it's just about justifiable in their case where they also want very high performance (high discharge rates), but it's arguable that sticking within the 150kW limit and having a lighter, slightly slower-charging, battery would make for a better all-round car.

For charging stations, 350kW total power shared between 4 stalls makes perfect sense - again, a modest step up from Tesla's 145kW shared between 2 stalls. Giving it 800V capability so that it can charge a single Porsche at higher rates seems questionable, but it needs to be developed for bus applications and maybe the cost increment is small enough that it can be affordable for car stations (especially if Porsche are offering a contribution).

And will the 3rd-party chargers just be "Plug in, and walk away" like Tesla is?

That's supposed to be supported (securely) in future CCS vehicles, and Fastned are apparently offering it now (insecurely) on existing CCS vehicles - just using the MAC address of the car to identify the account to be billed.

 

[Peteski]

Evening all,

I see Ecotricity have announced they will be rolling out their own 350kw fast chargers on the electric highway as of next spring. Wonder when/if Tesla will be enable charging at those speeds. I know they have mentioned rolling out superchargers rated that high but no EV's to date apart from the Porsche Mission E can take that kind of charge. There was also an interesting article on Electreks site listing the pro's and cons. It can be found here.

Just wondered what people's thoughts were on the subject?

My first thought is that there will be only a handful of cars that can theoretically make any use out of such a high charge rate and of those handful, how many of them are going to regularly use superchargers anyway? It seems more like a PR exercise to me. The only vehicles regularly plugging into those chargers in the next few years will be Leafs, Zoes, i3s, PHEVs and the odd Tesla! I suppose it may future proof their charging network, but that's about all.

 

[WannabeOwner]

it's not at all appropriate to 'spend' the improvements entirely on charging rate increase

I'm optimistic for better energy density and thus lighter/further battery in the Next Gen.

just using the MAC address of the car to identify the account to be billed

I suppose that's slightly better than Polar who only asked for my email address, over the phone, before initiating charging remotely

 

[jgwozdzicki]

I'l

I'm optimistic for better energy density and thus lighter/further battery in the Next Gen.

I agree @WannabeOwner. l'd be interested to see once the M3 production is under control whether they will look at the battery technology for the MS/X. Personally, i'd like to see some more options back other than 75kW and 100kW unless the packs can go further on the same charge. I don't think the 75kW isn't enough for me range wise at the moment but the 100kW is too expensive for me to justify the extra range. Be interesting to see how the Next Gen will work with the new charging technologies that are coming through.

Still, I'm happy to wait and see what happens.