Lucid EVs?

Just came across this on CNN but no mention of it here on ES that (at least that I could find). Anyone have any information to share?

https://www.cnn.com/videos/business/2020/08/11/lucid-air-electric-vehicle-orig.cnn-business

They use 21700 cells in their pack. I would not be too impressed by long range claims. The larger the battery, the heavier and more expensive the cost is.

I kind of figured that this didn't mean a battery breakthrough from the language they use on their own website: "Lucid’s proven world-class battery technology ..." Which pretty much means the same as everyone else uses.

One of Lucid's engineers sharing a ton of info on how they build their battery packs.

It's definitely worth a watch but the short version is they are brilliant.
https://youtu.be/2aDyjJ5wj64

That was pretty cool explanation of the pack modules and the simple benefits for which materials they went for.

As it usually tends to be, the impressive end result comes from smaller, incremental gains of currently available technology.

Spoiler alert for those who wish to hear it from the presenter....

-21700 cells - no major breakthroughs in chemistry for this version. Commercially available in many capacity flavors
-smaller gauge fuse connections from individual cells to a larger buss bar - well known for Tesla packs, I don't know if they use 2 sizes of fusing but makes sense to use a little less material
-aluminum buss bars for weight savings- probably also for availability since aluminum is easier to recycle these days
-proprietary BMS from a custom PCB design to fit into the module case - not a brand new idea, scooter packs and other small EVs use those

Making electrical connections from one side and dealing with temperature management from the other side is a first I have heard on a car. Interesting that the cell conducts heat more effectively in the axial direction, I wonder if that has something to do with the jelly roll internals since you have some insulation every other layer moving outward radially. Also injection molding the plastic case to encase the bus bar and stamping your heat exchanger together with internal baffles are a good little manufacturing time savers.

The ES user APL actually was messing around with a CAD drawing to do electrical connections on the same side so kudos to him, he could help design luxury touring EVs haha.

I would really like an in depth tear down of Lucid's racing pack set up and see what they do to push the limits of power on a track. Probably some great secret sauce in there.

The big takeaways for me were design and assembly simplicity, modularity, and working the design to the strengths / weaknesses of the components.
The plastic housing has the buss bars / battery connections molded in place. Batteries get loaded in the same direction then a machine likely welds the contacts and fuses. So easy to assemble.
There is a fuse and a contact per battery. Material in the inside is weight anyways, they size the contact to not conduct heat. The fuse connection will create some heat.

The current squared for heat was news to me. High voltage makes much more sense but is dangerous.

The cooling setup is extremely simple but counterintuitive. With the explanation of battery heat conducting better out the ends, it should work well. Only downside I see is 1kv heatsink to battery with only some type of (correctly durable and long life) thermal compound in between.

The bms attached to the side of the buss bars. No wires or other struggles to deal with.

They said the battery is 52v. Safe to build voltage wise.

Simple, modular, easy to assemble, well designed.

Hopefully lucid can get average people to understand how well engineered their cars seem to be. It's unfortunately not most people's motivation to buy.

Every cylinder cell EV pack I've been involved with since 2016 used bottom cooling with single sided cell interconnects. Glad to see others joining. We measure for clients the cell thermal conductivity radially vs longitudinally. Generally 20-30x higher W-mK in length than radius.

A few design changes would be needed before I would buy a vehicle with that pack, but that's because our business is running torture to failure battery tests, and I don't see it surviving pack heating and cooling cycles in a road salt spray chamber with that style of enclosure. IMHO the amount of displaced and ingested air volume from internal temperature change looks pretty scary to me.

Lots of well meaning folks run the SAE and ASTM salt spray standards which use distilled water and >99.9% Sodium Chloride salt. These salt spray test standards don't have the correct mix of ions to generate low temperature molten salt bridges. Real road salt that's thrown off tires in a mist of tiny aerosolized droplets contains around a dozen sulfate and chloride salts, which do readily enable corrosion induced failures including runaway.

Testing in California, for however many miles doesn't reveal these issues unfortunately, because the climate is mild. We have an EV battery recycling company, and a dominant reason we get EV packs to shred is internal condensate formation related corrosion effects. If each day your drive and warm your EV battery, then park it and let it cool off just a bit after sunset, as the pack cools the internal volume of air shrinks and normalizes atmospheric pressure by drawing in air. Gore vents stop liquid water but pass humidity preferentially to air molecules (because water vapor is lighter and smaller and faster moving than N2 and O2). I don't see any provisions to stop that humidity condensation trapping cycle that happens to folks who've been trying similar housing designs for the last many years.

There's good reason why even SpaceX pots there battery packs today, despite every gram being so precious.

Luke, this sealing to prevent salt vapor ingress is obviously important.
Which vehicle packs do you believe manage this issue best ?....if any ?

Hillhater said:

Luke, this sealing to prevent salt vapor ingress is obviously important.
Which vehicle packs do you believe manage this issue best ?....if any ?

Click to expand...

The packs that displace the bulk of the interior gas volume with something that doesn't migrate in and out of the pack as it changes temperatures or elevations tend to live (if they don't have other issues like resonance, dielectric breakdown of adhesives etc). If you fill the lungs volume, they stop being pumps.

This can be accomplished with lightweight closed cell foams, but it doesn't tend to help passive propagation resistance much. I prefer endothermic filler-loaded pottings, generally in a urethane family resin (unless clients material compatibility requires other base resins, but its the filler that does the work). These materials tend to yield amazing thermal runaway resistance at the tightest cell-to-cell spacings, but its significantly higher density than foam solutions to break the humidity ingress cycle.

From which vehicles perspective, this would mean the ones with potted cells. Fortunately, while no companies start out potted, many of the ones who stayed in business making products that survive in the field today are potting.

liveforphysics said:

Hillhater said:

Luke, this sealing to prevent salt vapor ingress is obviously important.
Which vehicle packs do you believe manage this issue best ?....if any ?

Click to expand...

From which vehicles perspective, this would mean the ones with potted cells. Fortunately, while no companies start out potted, many of the ones who stayed in business making products that survive in the field today are potting.

Click to expand...

I was not aware any of the current EV packs are potted ?
Tesla ?, GM( LG) ? , Rivian ?, Hyundai (LG) ?, BYD, ?
Is the move towards LFP cells also part of this ?

Sure, Teslas packs used to look like this:



After getting lots of field miles in various climates, they look like this:

Does spaceX pot their batteries to keep the vacuum out or air in? I imagine their thermal cycling is very demanding on components too.

I have to watch again. I think they didn't show the case well or get into the vent specs / function.
All speculation / possibilities:
If you seal it besides venting a battery event I imagine that could work (same air.)
Maybe they purge and fill the battery with argon or other "good" gas?
Might be able to work a dessicant, a valve, and a vacuum pump (to remove moisture from the dessicant) to only let clean dry air in.

Let's hope they start out with a dry gas, but after a handful of temperature cycles and/or altitude changes, it will not have made a difference on the starting gas composition. Same thing with desiccant packs, it just buys you an extra few cycles before it saturates with humidity and you're back needing to address the fundamental issue.

That housing is definitely not capable of a vapor tight seal, and they arent using the right materials or seal interfaces to have been trying for it to hold a pressure difference. There's another tricky factor for packs that do have a sealed housing, now you need to maintain defect free sealing over the life of product, or a pinhole leak developing anywhere becomes a safety concern.

Really is fascinating to get to do the battery autopsies for so many different sizes and manufacturers. It sounds like you are saying this is an industry wide issue not just cars and other larger vehicles but bikes and the smaller personal vehicles.

Is the condensation something that affects cells within a few years or seasons or weeks? Or is it something that builds over time in a larger vehicle like sludge in an engine? Engine sludge builds over time but something is severely wrong if it causes death of an engine in a few years. (Outliers, personal stories and extreme environments aside, I have no doubt someone can drop a story of their new gas car dying in the artic circle after just a few years.... )

MorbidlyObeseKoala said:

Really is fascinating to get to do the battery autopsies for so many different sizes and manufacturers. It sounds like you are saying this is an industry wide issue not just cars and other larger vehicles but bikes and the smaller personal vehicles.

Is the condensation something that affects cells within a few years or seasons or weeks? Or is it something that builds over time in a larger vehicle like sludge in an engine? Engine sludge builds over time but something is severely wrong if it causes death of an engine in a few years. (Outliers, personal stories and extreme environments aside, I have no doubt someone can drop a story of their new gas car dying in the artic circle after just a few years.... )

Click to expand...

Depends heavily on the climate and use case. It often takes a year or two to discover the depth of the issue.

liveforphysics said:

Depends heavily on the climate and use case. It often takes a year or two to discover the depth of the issue.

Click to expand...

I have to ask then, LFP- would the "Best" battery pack then, be one that is:

• Using Lucid style busbar connections

• Is fully potted once all connections are confirmed and is tested to work

• Has exposed ends for liquid cooling

Or is that just, a massive oversimplification?

CONSIDERABLE SHOUTING said:

liveforphysics said:

Depends heavily on the climate and use case. It often takes a year or two to discover the depth of the issue.

Click to expand...

I have to ask then, LFP- would the "Best" battery pack then, be one that is:

• Using Lucid style busbar connections

• Is fully potted once all connections are confirmed and is tested to work

• Has exposed ends for liquid cooling

Or is that just, a massive oversimplification?

Click to expand...

Nope, its just saving money to use cylindrical of course. Cylinder cells are the cheapest $/Wh you can get for electrochemical energy storage units. If you've got an application where your goal is words like "best" battery pack, its going to be Z-fold pouch, and you use cells with a native impedance enabling intrinsic temperature stability on your worst-case drive profile without the liabilities and failure modes and service of liquid cooling loops. This style of pack would be a massive performance upgrade in every metric from performance and range to longevity.

OEM's sadly have never tried for "best", they go for most cost-effective solution to meet minimum product specs.

liveforphysics said:

CONSIDERABLE SHOUTING said:

liveforphysics said:

Depends heavily on the climate and use case. It often takes a year or two to discover the depth of the issue.

Click to expand...

I have to ask then, LFP- would the "Best" battery pack then, be one that is:

• Using Lucid style busbar connections

• Is fully potted once all connections are confirmed and is tested to work

• Has exposed ends for liquid cooling

Or is that just, a massive oversimplification?

Click to expand...

Nope, its just saving money to use cylindrical of course. Cylinder cells are the cheapest $/Wh you can get for electrochemical energy storage units. If you've got an application where your goal is words like "best" battery pack, its going to be Z-fold pouch, and you use cells with a native impedance enabling intrinsic temperature stability on your worst-case drive profile without the liabilities and failure modes and service of liquid cooling loops. This style of pack would be a massive performance upgrade in every metric from performance and range to longevity.

OEM's sadly have never tried for "best", they go for most cost-effective solution to meet minimum product specs.

Click to expand...

Huh. I keep finding more to learn.

Odd question, but do you respond much to personal email about education, college and such? I have some questions about the industry.

liveforphysics said:

Hillhater said:

Luke, this sealing to prevent salt vapor ingress is obviously important.
Which vehicle packs do you believe manage this issue best ?....if any ?

Click to expand...

The packs that displace the bulk of the interior gas volume with something that doesn't migrate in and out of the pack as it changes temperatures or elevations tend to live (if they don't have other issues like resonance, dielectric breakdown of adhesives etc). If you fill the lungs volume, they stop being pumps.

This can be accomplished with lightweight closed cell foams, but it doesn't tend to help passive propagation resistance much. I prefer endothermic filler-loaded pottings, generally in a urethane family resin (unless clients material compatibility requires other base resins, but its the filler that does the work). These materials tend to yield amazing thermal runaway resistance at the tightest cell-to-cell spacings, but its significantly higher density than foam solutions to break the humidity ingress cycle.

From which vehicles perspective, this would mean the ones with potted cells. Fortunately, while no companies start out potted, many of the ones who stayed in business making products that survive in the field today are potting.

Click to expand...

Pack shells could be made to oil can a bit with bimetal in wall sections to help with temp swings and possibly also tuned to take care of some of the atmospheric pressure swings. Difficult to keep moisture out long term without some drying from AC or other active method.