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Interesting article on GMs new pack architecture:
https://arstechnica.com/cars/2020/0...nces-new-battery-platform-claims-100kwh-soon/
https://arstechnica.com/cars/2020/0...nces-new-battery-platform-claims-100kwh-soon/
GM Ultium batteries
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Once we start getting wrecked ultiums I will drop one in my c-car
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They’re designed to sit on a cooling plate. I don’t think a module will just “drop in”
The caption for the first image includes this:
The cells in the Volt, Spark EV, and Bolt are all vertical (standing on edge). For some reason GM's marketing people decided to hail the ability to place the cell plane either horizontally or vertically as some sort of big advance, and the writers who know almost nothing about EV designs are running with that.
Here's the GM statement about that orientation issue, as paraphrased by the writer of this article:
This all makes sense, but it's not new. The Volt, Spark EV (2014+), and Bolt all use LG Chem pouch cells. Almost all current production EVs other than those from Tesla use pouch cells. The original Nissan Leaf battery design (but not the new 63 kWh variant) places pouch cells horizontally under the seats and rear seat floor, but vertically under the rear seat where more height is available.
With not much change from the Bolt battery - at least from the limited descriptions available so far - you don't need to wait... just use the Bolt bits. If you really mean the whole pack... that's tough in any vehicle because packs and vehicles are designed to go together; what do you mean by "c-car"?
That's an important point: there's substantially more to designing and building a pack than just packing a bunch of them in a box. That's especially true for modules needing active thermal management, and most challenging for modules like this which need an external heat transfer plate.
The article says:
That's just about 8 kWh per module, or one-third more capacity than the larger of the two current Bolt module sizes, which have a 10S 3P configuration. The higher-capacity pack configurations would presumably have half as many cells in series (and twice as many in parallel) in each module to get 400 V in 12 modules and 800 V in 24 modules, with the same 8 kWh per module.
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And now the motors:
arstechnica.com
This is GM’s new series of Ultium Drive electric motors
GM will have 22 new EVs on sale by 2023, and they'll all use these motors.
arstechnica.com
No surprises, but it's good to see some information. Now for some notes about details that are suggested by this material, but not specifically mentioned in the article...And now the motors:
This is GM’s new series of Ultium Drive electric motors
GM will have 22 new EVs on sale by 2023, and they'll all use these motors.
The motors are bar-wound (or "hairpin"), like the Remy (now BorgWarner) motors that they used in the Two-Mode hybrids and the motors in the Spark and Bolt. An SAE paper about the design of the Bolt motor mentioned going to 6 conductors per slot from the Spark's 4 conductors per slot, but the image showing hand assembly of a pre-production motor looks like they're back to four, at least in this particular motor.
Ignoring the nonsensical wording ("induction magnet") it's interesting to see that they are taking the approach of using permanent magnet synchronous motors in general, but induction motors to minimize drag (and cost) where the motor is normally spinning unpowered (the "assist" unit).
It appears that GM is moving away from the hollow motor shaft and concentric (motor and axle) configuration of the Spark and Bolt to a more conventional layout... although not all units are shown in detail. The AWD assist unit seems to be the exception, appearing to be a concentric design (with a strange extra housing protrusion, unless it's a dual-motor unit which would be good).
In the AWD set of components on display, the rear unit appears to place the motor behind the axle line, while the front motor is ahead of the axle line. This makes sense to maximize space available within the wheelbase for the battery pack. Of course the difference between front and rear units is primarily that the inverter package is on top of the front unit (and the truck unit), and on the side (front side) of the car rear unit to minimize height.
Only three motors - one of which is an assist unit that is probably quite low-powered - doesn't seem like much variation for the company's entire product range. It will presumably be like the generation of Nissan Leaf: one motor limited to various power levels due to other components of the system (mostly battery), so the smallest cars haul extra motor weight around and the most powerful run the motor at screaming high temperatures if pushed hard. That might be okay, and will make aftermarket modification and DIY use easier.
That is how it works with engines now - a Corvette and a Silverado pickup are not similar, but have the same engine with only tiny variations. The drive units will be even more similar, because much of the performance variation between vehicles will be due to battery differences. The nice thing about the EV drive units is that nearly every wrecked vehicle will a source of a salvaged drive unit or two, since the motors and very simple gearboxes should have no problem outliving the vehicles that they're in.
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"I'm hoping the compact packaging allows them to put them in wildly different cars that only need similar power delivery...Millions of "standard" motors flooding junkyards like so many small blocks. "
And that is why this is such an awful idea!
GM has NOT got the message!
An EV is not a petrol car with a different power unit
To be a good EV you need to throw away all of the petrol bits and design the car from scratch as an EV
If you don't do that you get a dog and Tesla eats your lunch
Having deep "parts bins" was an advantage in the petrol days but turns into a disadvantage when the market changes to EV's
And that is why this is such an awful idea!
GM has NOT got the message!
An EV is not a petrol car with a different power unit
To be a good EV you need to throw away all of the petrol bits and design the car from scratch as an EV
If you don't do that you get a dog and Tesla eats your lunch
Having deep "parts bins" was an advantage in the petrol days but turns into a disadvantage when the market changes to EV's
Duncan, I think that you completely misunderstood the comment. There is no use of petrol engine powertrain components in the new GM products. Just like with engines, there are components which can be used over a range of vehicles: just as one engine family works in both sports cars and pickup trucks; one EV drive unit can work in various cars. Tremelune is just hoping that after a few years of production there will be many interchangeable GM EV drive units in salvage yards, just as there are now many nearly interchangeable GM small-block V8 engines in salvage yards.
And although this discussion is only about powertrain, much of a vehicle really is the same regardless of powertrain. A Tesla Model S/X rear suspension is nearly indistinguishable from the many large sedan "integral link" suspensions in many brands of cars; a Tesla Model 3 rear suspension is indistinguishable from the common five-link IRS systems in everything from Mercedes sedans of the 1980's to current Mazda Miatas.
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Hi Brian
Nope I understand the ideas - but I can also see that the old car engine thinking is prevalent in the GM organization
With a dino burner the engine is the "core" you build the car around the engine
GM are using the same thought train with these engines - and its simply the wrong way of thinking with an EV
The "core" of an EV is the battery - the motor is small enough not to be a major issue
Nope I understand the ideas - but I can also see that the old car engine thinking is prevalent in the GM organization
With a dino burner the engine is the "core" you build the car around the engine
GM are using the same thought train with these engines - and its simply the wrong way of thinking with an EV
The "core" of an EV is the battery - the motor is small enough not to be a major issue
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Management apparently wants to spit motors out like jellybeans and minimize production types, so telling the engineers, "here are the motors, go design your car", which seems opposite to Tesla's bespoke motor per model (which is not sustainable as competition heats up) and I think is the winning strategy to bring sub-$30k EVs to market. Tesla will soon have several motors as well, I'd suspect.
I agree the battery is the core of the vehicle platform design, but frankly I'm not thrilled with GM's idea of a wireless BMS. Too much PowerPoint in these established companies.
More interesting to me is the steering rear wheels on the new eHummer. Seems to have a lot more angular compliance than the rear steer in my GMC. There's around a 2HP motor back there in mine to move the wheels....range sucker.
I agree the battery is the core of the vehicle platform design, but frankly I'm not thrilled with GM's idea of a wireless BMS. Too much PowerPoint in these established companies.
More interesting to me is the steering rear wheels on the new eHummer. Seems to have a lot more angular compliance than the rear steer in my GMC. There's around a 2HP motor back there in mine to move the wheels....range sucker.
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Anyone have the PDF to that paper that they can PM to me?
No, you don't build the car around the engine. This is obvious, because many cars are available with a range of significantly different engines, and very different cars are built with the same engine. The engine location and orientation is an important feature of the design, just as the location, shape, and size of the battery (more than the motor) is an important feature of an EV's design.
There is nothing in the GM announcement which suggests that they are designing vehicles around the motors, or the drive units. They have just shown a set of drive units (built with only three different motors) to meet the range of requirements of their wide range of vehicles.
It's strange how some people in a forum for an inherently technical activity seem to have so little respect for technical professionals. The engineers developed the motor and drive unit range, within budgetary limits approved by management in response to professionally developed financial requests. That's how the real world works; to assume that engineers are helpless idiots following whatever technical direction comes from some executive is insulting.
It's also interesting how in this discussion there are two completely opposite ideas of best practice, both supported by reference to Tesla. Either a minimum of different motors or a bespoke motor for every model and variant is right, but either way someone thinks that is what Tesla does.
In fact Tesla only builds two models (with two body variants of each one), and they are from different generations (several years apart), so it's hard to tell what their idea of best practice might be.
Not me - I've only read the abstract. You could try a local university with an engineering faculty - they often have SAE publications, and some allow the public to use their resources within the library. Of course, that won't get you a PDF copy, for which you would legally need to pay.
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