Mercedes-Benz's Newest Electric City Bus Uses Solid-State Batteries (arstechnica.com) 61
An anonymous reader quotes a report from Ars Technica: Mercedes-Benz just announced that its new eCitaro and eCitaro G city buses will be available with roof-mounted solid-state battery packs, developed in conjunction with the Canadian power company Hydro Quebec. Although details are still rather limited right now, Mercedes-Benz says that the solid-state pack has a 25-percent higher energy density than even the most advanced lithium-ion chemistry. It also says that the solid-state battery has a much better service life than lithium-ion and is warrantying these batteries for 10 years or an energy throughput of 280MWh. When configured with a total of 441kWh onboard (composed of seven 63kWh packs), an eCitaro G has a range of up to 137 miles (220km) under favorable conditions, or 105 miles (170km) in the depth of winter with the bus's heaters running.
However, these solid-state batteries aren't perfect. In particular, they aren't able to fast-charge at rates comparable to lithium-ion, which is why Mercedes-Benz is also offering the bus with an optional lithium-ion pack that can be charged at 150kW or even 300kW instead. This uses a nickel-manganese-cobalt chemistry and comes in assemblies of 33kWh that can be combined to give a bus up to 396kWh in total. "In a traditional battery, a pair of electrodes are immersed in an electrolyte solution, and it's this liquid electrolyte that allows ions to move from one electrode to the other," the report adds. "But liquid electrolytes can leak, and that's not a great thing, whether the material is highly corrosive, as in a lead-acid battery, or highly flammable, as in a lithium-ion battery. So researchers around the world have been experimenting with batteries that use a solid electrolyte instead, with a particular eye on using them in electric vehicles."
Further reading: The Slashdot Interview With Lithium-Ion Battery Inventor John B. Goodenough
However, these solid-state batteries aren't perfect. In particular, they aren't able to fast-charge at rates comparable to lithium-ion, which is why Mercedes-Benz is also offering the bus with an optional lithium-ion pack that can be charged at 150kW or even 300kW instead. This uses a nickel-manganese-cobalt chemistry and comes in assemblies of 33kWh that can be combined to give a bus up to 396kWh in total. "In a traditional battery, a pair of electrodes are immersed in an electrolyte solution, and it's this liquid electrolyte that allows ions to move from one electrode to the other," the report adds. "But liquid electrolytes can leak, and that's not a great thing, whether the material is highly corrosive, as in a lead-acid battery, or highly flammable, as in a lithium-ion battery. So researchers around the world have been experimenting with batteries that use a solid electrolyte instead, with a particular eye on using them in electric vehicles."
Further reading: The Slashdot Interview With Lithium-Ion Battery Inventor John B. Goodenough
Manufacturing (Score:1)
Manufacturing is 100 times harder than building a prototype. Why do you think so many kickstarters fail? Unless Mercedes can show they have something highly manufacturable at a reasonable cost they're just jokers. Mercedes is stuck with ICE manufacturing lines that are a huge liablity. I wish them good luck though, I think Tesla needs competition but so far .. for at least the past decade .. everyone has been all talk. Now all these dinosaur car companies are claiming by 2025 they will have models to compet
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I particularly like the dig about how manufacturing things is hard and MB couldn't figure out how to move from prototype to production. Mercedes is the oldest car company on the planet. They have a little bit of experience in bringing things from prototype to market I would think.
That said, I am still unsure if Mercedes is truly giving electric vehicles the attention they deserve, vs giving them lip service while trying to stick with ICE as long as possible. Thing is, this article is an indicator that they
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Re: Manufacturing (Score:1)
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The big unsolved part about BEVs are the batteries right now. Tesla has invested heavily in lithium batteries because so far thats been the best around. And while they have done a lot to advance BEVs the bottleneck is still the batteries. The market can't really support every major car maker going big into BEVs right now. So while what Tesla does works for them it is not yet viable for the rest of the industry. We need safer, cleaner, better performing batteries that don't rely on exotic materials that come
To be clear: (Score:5, Informative)
* 25% more energy density than a not-particularly-high-energy-density NMC
* Vastly slower charge rate (a major problem with solid state in general, because you're trying to conduct ions as fast through a solid as through a liquid, and getting them off the surface and deeper into the electrodes poses its own problems
It's important to note that "solid state" is not a single technology. There's all sorts of different types of membranes. Some use liquid electrolytes in addition to a solid membrane ("partial solid state")**, some use particles of solid electrolyte mixed into the anode and/or cathode (greater ion penetration, lower Ah/g), and some use neither (particularly for Li-metal anodes). Often solid state is intended for the ultimate goal of using lithium metal anodes, but they can and frequently are made with any kind of anode, including normal graphite anodes. Nor is solid state the only way to achieve lithium metal anodes (and silicon anodes are nearly as good). In short, just saying "solid state" means almost nothing except for hype. It makes people think "next-gen superbattery" when they hear it.
** - As an example: while Tesla didn't use the term in their presentation, their Roadrunner cells are actually partial solid state. The anode and cathode particles are individually surrounded by solid-state membranes (ion-and-electrically-conductive) which function as an artificial SEI and allow for high-nickel cathodes / silicon anodes - but the separator membrane is conventional and the electrolyte liquid, so there's no rate problems as in a full solid-state cell.
The things to look for in a meaningful battery development aren't the words "solid state". For EVs, the number one thing is $/kWh, both unit cost and production capital costs. #2 in importance is high C-rates, for fast charging. For aircraft, the number one thing is kWh/kg (only moderate C-rates needed). For ships, it's a balance of both $/kWh and kWh/kg at the same time (C-rates are almost irrelevant).
Re:To be clear: (Score:4, Interesting)
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>"That was my response as well, WTF is a "solid-state battery"?"
I think this is a translation error or some marketing crap. As far as I am aware, there is no such thing as a "solid state battery." I think what is meant is a solid materials battery, as opposed to batteries that use fluids or semi-fluid components.
With the exception of rare "flow batteries", no electric battery has moving parts, so in that sense, they are all "solid-state batteries."
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The term "solid state" is in common use [thefreedictionary.com] to describe materials that are solid. A solid-state battery contains no liquids. Solid-state electronics don't use gases. The outlier is SSD: harddisks are solid-state too (no gases or liquids used, unless you consider the elimination of the lubricant to be the most significant part in the move from HDD to SSD).
Re:To be clear: (Score:5, Informative)
Uh, an HDD requires a gas to operate. The vast majority of them work in regular air, some fancy ones use helium. None will work in a vacuum.
The gas in an HDD allows the heads to "fly" over the platters without touching them. Bad things happen if the heads touch the platters (usually called a disk crash, as in the heads crashed into the platters and took out a chunk of magnetic material).
Old school hard drives needed their heads parked which moved them into a safe cylinder where they could gently land on the platters - no data was stored there so even when it got scraped it didn't damage the data region. Modern era drives (which really date to late 80s) use voice coil motors which move the heads into a special parking zone off the platters - there's a comb-like stand that holds the heads apart and removes them from the platters so as long as the heads stay on the stand, they will not crash into the platter because they're off the platters. Since voice coil motors are much faster, they don't need to be parked - you can issue them a spin down command (or unload head command) which will park the heads gently in a controlled manner, or just yank power to the drive. The drive will use the spinning platters as an energy source to quickly move the heads to the parking stand. It's why the parking clunk you hear varies - the OS level drivers park the heads and it's a soft gentle unload, but if you just unplug the power it makes a very loud clunk because it basically dumps the motor's energy into the voice coils to fling the heads into the parking area.
Hard drives have an altitude limit as well - go higher than that and the air is too thin to maintain flying height of the heads.
And of course, it means they do not work in a vacuum.
SSDs have no moving parts (another thing that usually differentiates "Solid State" from non-solid-state stuff), and do not require air to operate.
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The term also means, and usually does when talking about electronics, no moving parts. HDDs are not solid state because they both have moving parts, the platters and head, but they also do rely on gas as tlhIngan noted. Relays traditionally are also not solid state. Nor are Vacuum tubes. Transistors, diodes, resistors etc all are.
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The energy and power density will always be more exciting, and has the added effect of costs coming down automatically as less material is being used for a given amount of en
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Range isn't actually limited by Wh/kg or Wh/l. The Model 3 for example is roughly weight-equivalent to its performance-and-class equivalents from BMW. There's neither a weight nor a volume reason that prevents manufacturers from using thicker battery packs; extra weight and extra floor thicknesses isn't a "good thing", certainly, but it's not prohibitive, either. The thing that has kept manufacturers from going with larger packs for longer ranges is the impact it would have on the price and profitability o
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I'm even more interested in the longevity of these batteries since that would be even more interesting for operation in the long run. If they still are viable after 10 years and might even last for 20 or 25 years then they would be essentially good for the lifetime of the vehicle. Same if they could be used in phones.
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Busses are ideal for this kind of battery because their duty cycle and daily driving distance fits the charging profile well.
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Most buses are stored overnight at a depot, so as long as the bus can get through its daily schedule without recharging, a slow charge rate isn't really a problem.
The 11foot8 bridge approves roof mounting (Score:4, Funny)
of high density battery packs.
Eagerly awaiting for the first candidate to make first contact.
https://www.youtube.com/yovo68 [youtube.com]
Re: The 11foot8 bridge approves roof mounting (Score:1)
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That's likely one of the reasons for mounting them on the roof... Heat rises, so if the roof catches fire the flames and smoke will rise up into the air leaving the passengers below time to escape.
If the batteries were under the floor and caught fire, the heat and smoke would be going into or around the passenger area of the bus, hindering escape.
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If the batteries were under the floor and caught fire, the heat and smoke would be going into or around the passenger area of the bus, hindering escape.
Yeah, but they won't fall through the roof on top of their heads. And you better put wheels on the roof too. the thing will flip right over with the center of gravity that high up.
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11foot8 has been raised. Sorry to inform you.
https://mashable.com/article/1... [mashable.com]
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It's now 11' 8+8"
And it won't help, it has experienced new crashes recently.
https://www.youtube.com/watch?... [youtube.com]
https://www.youtube.com/watch?... [youtube.com]
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with bridges like that, why would they raise the bridge as opposed to just lowering the road? It seems like it would be more practical to just dig the road a few feet deeper into the ground.
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If I remember right they did lower the road with some 8" recently.
But to ensure that "everyone" can pass then they'd need to get a 15 foot clearance.
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Everything I could find said that they "raised" the bridge. But I suppose that could actually mean that they really did lower the road instead. Since trucks keep hitting it, it obviously wasn't enough. They really should have just gone the additional 2' 8" to make it 15'. Looking at it from above, it looks like about 20 feet to the intersection, so a drop of 3' 4" over twenty feet would be about a 9.5 degree angle. That's higher than the grade allowed for highways in the US, but plenty of local streets have
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It's hardly the only example around.
We had one in my city at about 7' and only a block away from one of the main bus depots in town. Buses returning to the depot slammed in to it all the time (the drivers usually stated they forgot they were in a bus vs their personal vehicle). The city recently gave up and just completely closed that street to traffic. It was low use anyway, and I guess they got sick of writing off buses.
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We recently had an accident where a bus drove into a bridge and the kids on the top deck were injured. I'm surprised we don't have a warning system for that kind of thing yet, similar to AEB in cars but for the top of the bus.
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It's a pretty hard problem to solve because you have to measure bridge height at a distance. By the time you get close enough for naive sensors to work, it's probably too late to brake.
You could solve the problem by requiring buses to slow down when going under overpasses, but that would perturb traffic for everyone else in many situations.
The best solution is to get rid of buses. The one and only reason we use them is that drivers are expensive. If self-driving really comes true, buses will go away. Vans c
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You could put some transmitters well before the bridge that signal its height. The bus picks the information up and warns the driver to use a different route. If they don't turn off at the last possible exit it slows the bus down to a gentle stop.
Actually these days they could just do it with a basic sat nav system and database of bridges.
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Systems like the former exist, but adoption is poor. There are also signs that detect approaching tall vehicles and announce that they will not clear, but they are expensive and so adoption is poor.
Trucker satnav which knows bridge heights exists, but it depends to an extent on cities, states, and localities accurately reporting clearance, which as you might imagine is not reliable (because adoption is poor) ;)
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A row of hanging balls ahead of time, with a way to divert, has become downright common for parking garages.
If you hear a whump-whump over your head as you drive under, and don't figure out what it means, well . . .
hawk
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We're talking about countries with real public transport, not the USA.
So do thieves . . . (Score:2)
Think of how much easier it will be to steal these conveniently mounted top batteries.
Why, a particularly clever ring could jump on at one overpass, harvest part in time for a subsequent one, and be gone b before noticed . . .
Rioters will also appreciate the greater accessibility . . .
hawk
We have in-air refuelling, why not battery swaps? (Score:3)
We have in-air refuelling, why not battery swaps? Why the sustained focus on charging?
As for safety, surely manual/machine-assisted/robotic battery swaps can be made even safer than pumping flammable gasoline.
Stretching the idea further: aircraft refuelling can be done mid-air. So a road-based battery drone that docks while the vehicle is rolling and swaps batteries should be possible. The drones could operate a few miles up and down their hubs, or on a highway, or (probably better) in purpose built 'reload lanes'.
Re: We have in-air refuelling, why not battery swa (Score:1)
But.
Only a few routes are near the depot.
The depot will need its own power feed straight from the high voltage transmission lines if it's going to have dozens or scores of batteries constantly charging. That's several dozen per route.
There is already a solution for having electric powered city buses. It is called the trolleybus and it does not require a 100 mile range battery on its roof, nor
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Such a bus basically becomes a train...
It requires infrastructure built along its entire route, cannot deviate from that route when conditions require, and requires building of new infrastructure if the route ever has to change. A normal bus can travel anywhere that has roads.
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We used to have electric buses with overhead wires. It's not all that bad an option (and saves you on all this battery stuff!)
That said, I keep seeing all sorts of things about battery powered trains, and I really just don't get how that's ever a good idea. It's a train, it's on tracks, why go battery when you can either energize the tracks, or use overhead wires? This is a solved problem, adding batteries adds a lot of expense, and I just can't see the benefit.
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I agree. Trolley buses are interesting but seems more like a train with overhead rails for power. They seem to have their place in mass transit but don't always go where/when/how one want them to.
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It's not exactly as if city buses deviate all that much from a train-like route anyway. These aren't taxis. They're meant to maintain rigid routes and schedules. There doesn't seem to be any reason that you couldn't just build a battery swap device/charger into any bus stop. The bus stop would obviously need to be reinforced, but you could certainly build in something that could quickly lift off a section of battery from the roof and drop in a charged replacement and then charge the removed section for a la
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I'm not sure why any of that would be necessary. Also, yes, like overhead wires, as I mentioned, just not overhead, but built into the road itself. Do you maybe have a legitimate criticism of what I wrote? Maybe some cost estimates? Assessments of the technologies required and the current state of those technologies? Maybe even some safety concerns? You know, something to actually stimulate real discussion rather than just hollow mocking with unrelated strawman arguments.
I'll readily admit that it c
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I was thinking more in terms of service stations.
These tend fleets of 'battery drones' with topped up batteries wait adjacent to 'reload lanes'. A car slows down and enters a reload lane at a reduced speed. As it keeps rolling, its e-tag pays the reload fee, or ALPR / computer vision recognises the car and its preregistered biller. A battery drone behind the car then scoots up behind it, docks, and implements the swap. It undocks and moves out of the reload lane, to automatically trickle charge the deplete
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So you don't have to stop, get out and swap a 100 kg battery risking life and limb (like reloading the APU Mech Robots in Matrix Revolutions) :-)
It'll be more like going through an electronic tollbooth.
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That's actually a good idea. Or a car drives onto a concrete ramp, with a gap in the centre.
Like so
https://wiki.openstreetmap.org... [openstreetmap.org]
Imagine Amazon Kiva-like robots scurrying around in the gap below automatically, rearranging battery packs. The first collects 'empties', then loads charge canisters in conjunction with a mechanism in the vehicle. I imagine these canisters to be something like gas bottles.
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In-air refuelling is exceptionally expensive, inefficient and very risky. Next question?
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That's (half) my point. In comparison to mid-air refuelling, automating battery swaps on land is simple.
Manual refuelling works fine for gas vehicles . So electric vehicles copied it, just substituting the pump hose with a power cable. The problem is batteries aren't empty steel tanks - they take hours to charge.
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Tesla *tried* swappable packs for charging.
People just didn't use it, and they dropped it.
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Thanks -- just googled: https://electrek.co/2016/05/10... [electrek.co]
Hindsight yes, but it seemed set to fail: it was offered in few locations, was competing with free ("the Supercharger network is free to use to all Model S and X drivers, while a battery swap costs $80."), was eventually modified so it was no longer automated and took 15 minutes, and you had to swap out your entire battery (no such thing as half a battery swap) -- that means there was no point 'topping up'.
A fully automated swap of multiple battery mo
Why on the roof? (Score:3)
Would it not make the structure of the buss heavier? Not to mention high CG?
So what is the advantage to put a heavy load on the roof?
Re:Why on the roof? (Score:4, Insightful)
Can't put it in the floor without hurting accessibility. Modern city buses are low enough that you can use a ramp rather than a lift to load wheelchair users which is a lot faster, and the floor is flat which is safer for standing passengers. This all needs a thin floor structure. The roof is a space where you can put bulky equipment of various types without affecting the design of the rest of the bus very much. Makes it easy to reconfigure the battery packs or turn it into a trolleybus later too. High CG isn't that important, buses are not driven like sports cars.
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I was pretty sure that was a trivial question I knew the answer to. I'd think there is still a lot of space under the floor despite it being perhaps one step up? The roof cannot be thicker than one standard step, can it? Hard to tell from the picts.
The high CG would make it a wobbly ride, would not it?
Reconfigurability did not occur to me - that's a good thought! Thought perhaps this whole design is a adaptation of an existing platform that already had low floor and limited space there for batteries.
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In Sydney they've been mounting large CNG storage systems and air conditioners on the roofs of low-floor buses for decades. It doesn't seem to cause a problem.
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There are some buses with an upper deck, these always look like they're going to tip over on cornering but there are still heavy components like the engine kept low down. But buses don't do aggressive cornering, so with proper driver training it shouldn't be a problem.
Having batteries under the floor is not ideal if they are potentially a fire hazard, flames and smoke from a fire tend to go upwards...
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And yet basically every EV has them in the floor, and when there are fires, nobody's been hurt (not from the fire, sometimes the crash that caused the fire also caused other injuries). So I'm pretty skeptical of that idea.
I suspect the real truth of the matter is that MB found it was cheaper/easier to retrofit an existing design by swapping the engine for an electric motor, and bolting a battery pack to the roof, than doing a complete redesign to properly distribute batteries under the floor. Unfortunately
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I suspect the real truth of the matter is that MB found it was cheaper/easier to retrofit an existing design by swapping the engine for an electric motor, and bolting a battery pack to the roof, than doing a complete redesign to properly distribute batteries under the floor.
I'd bet money you're correct. They used a bus designed for CNG, with the tanks on top. Natgas rises while propane descends, so for LPG you want tanks underneath, but commercial vehicles use CNG or LNG instead (more energy density) you usually put the tanks on the roof where leaks will rise away and dissipate. It also gets the tanks up out of the crash zone where other vehicles are unlikely to hit them. Buses rarely roll over fully, they mostly just turn onto their side.
I have experience driving a bus on my