Q&A with Lucid’s Battery Cell Technical Specialist Maithri Venkat.
With regards to battery cells for EVs, one dimension undoubtedly doesn’t match all. The properties of a specific cell act as constraining components for each facet of a automobile’s design—and never just for automobile efficiency parameters equivalent to vary and energy, however for the event of producing processes as nicely.
Lucid Motors has a staff of battery specialists that collaborates intently with cell suppliers to guage and check battery cells at each step from automobile design by means of mass manufacturing. Charged spoke with Lucid Battery Cell Technical Specialist Maithri Venkat about how cell analysis works, and the way OEMs and cell suppliers can work collectively to enhance the method.
Charged: Might you inform us about your self and your journey to your current position at Lucid Motors?
Maithri Venkat: I’ve been working in lithium-ion cell improvement for automotive functions for the previous eight years. In my present position as a Technical Specialist at Lucid, I lead next-generation cell choice, qualification and key provider partnerships for the Gravity SUV. I’ve labored on a number of elements of battery improvement, from cell materials analysis to design tradeoff assessments to efficiency optimization and new product introduction.
Beforehand, I labored at XALT Vitality, the place I benchmarked cell designs and sub-components for high-energy cells for transportation and marine necessities. I’ve additionally collaborated with top-tier OEMs and nationwide labs for 12 V Li-ion begin/cease battery improvement.
Charged: Are you able to elaborate on why battery cell improvement is so essential for electrical automobiles?
Maithri Venkat: As automakers decide to electrification, the market necessities have gotten extra numerous for several types of EV merchandise—longer vary, sooner charging, sports activities car-level efficiency numbers and lengthy life. The battery cell impacts all of those.
How one designs, tunes and manufactures the battery cells additionally impacts their effectiveness, efficiency and price. For efficiency functions, an organization must know learn how to push the restrict. For financial system choices, the cells are the most important price driver within the automobile.
Battery cell improvement is vital at each step of the event of a automobile, however particularly at the start conceptual design section, the place the vehicle-level product definitions are translated into cell-level technical specs. Technical assessments and industrial necessities are evaluated by EV producers throughout cell choice and qualification. As soon as the cell design is finalized, it’s fine-tuned additional for power effectivity, quick cost functionality, energy functionality and lifelong necessities, previous to deployment in packs and automobiles. This early stage of cell improvement paves the best way for best-in-class technological developments.
Charged: Are you able to stroll us by means of the preliminary phases of the cell qualification course of? What do we have to think about even earlier than going into cell choice?
Maithri Venkat: Cell improvement for automotive functions must occur years upfront. This ensures that now we have sufficient time to iterate by means of cell design modifications. Typically, cell improvement begins with the creation of vehicle-level efficiency targets.
For instance, a automobile’s supposed usable vary is a key metric within the qualification course of. Goal vary necessities are outlined based mostly on an array of analysis, together with advertising surveys and client suggestions. With these established, we will apply technical constraints equivalent to automobile and powertrain effectivity, pack sizing and automobile weight class, to remodel vary into usable power per cell.
Previous to defining battery pack constraints, we have to analyze and steadiness efficiency, sturdiness and price. This requires in-depth collaboration amongst cell engineering, techniques, automobile integration, effectivity, software program and advertising groups.
Following automobile definitions and alignment on cell efficiency aims, specification sheets are despatched over to cell suppliers. This creates an iterative suggestions loop between OEM and cell provider, and triggers hole evaluation between necessities and know-how readiness.
Figuring out these efficiency gaps and quantitatively understanding the constraints of particular cell chemistries helps with future cell improvement. For example, for high-energy cell design, material-level modifications equivalent to silicon for anodes, high-nickel cathodes, or solid-state chemistries could possibly be thought-about. This may allow technological developments and outline clear actionable aims to bridge the variations between current-generation and next-generation applied sciences.
Charged: You talked about the necessity to translate vehicle-level necessities into cell-level targets. How will we accomplish that?
Maithri Venkat: As soon as the automobile conceptual design has been finalized, necessities trickle right down to pack and module ranges earlier than getting right down to cell-level definitions.
Each high-level goal could be tied to a person parameter of the battery cell. For instance, pack dimension, effectivity and vary could be outlined as power necessities for the cell. 20-80% SoC (state of cost) charging instances could be translated to quick cost functionality of the cell. Product guarantee necessities [can be translated to] lifetime efficiency of the cell, and so forth. Type issue choice could be depending on pack sizing methods, thermal administration techniques for cooling, ease of manufacturability, and even ease of restore.
Cell peak or steady energy targets are associated to the 0-60 mph automobile efficiency necessities and towing capability. Detailed energy functionality evaluation is useful to supply the required efficiency while you wish to—for instance—tow your jet ski to Lake Tahoe. Or, on the best way house, roll down a hill and regeneratively brake at freezing ambient temperatures for over an hour.
Charged: What are the steps an organization takes to qualify a brand new cell provider?
Maithri Venkat: We consider cell suppliers for a number of prime priorities, together with security, high quality, price, efficiency, volumes, know-how roadmap and know-how capabilities.
For instance, in the case of cell high quality inspection, manufacturing batch lot-to-lot variation should be inside the outlined engineering specs, and course of variations ought to be inside Six Sigma management limits. Within the preliminary phases, routine beauty and electrochemical inspections should be performed on obtainable samples. Cell dimensional properties and look of dents, rust or scratches ought to be completely assessed to grasp manufacturing course of functionality. For electrochemical inspection, it could even be advantageous to conduct common testing for efficiency traits like power and resistance. If cell-to-cell power variations exceed sure threshold values, there are dangers when it comes to battery pack imbalances.
One other facet to contemplate is the provider timeline. Auto producers want to make sure that their improvement timeline aligns with the cell producer’s milestones for idea, design and course of validation phases. Cell mass manufacturing ought to be nicely upfront of the product introduction timeline.
Charged: As soon as a cell design is finalized, what are the following steps to be thought-about? What varieties of checks are acceptable for every developmental section?
Maithri Venkat: Following cell design finalization, a number of workstreams occur in parallel as a part of the product improvement cycle. I’m presently main and facilitating these efforts for Lucid’s Gravity SUV platform. These embrace quick cost, sturdiness, course of functionality, cell parameterization for software program controls, and testing for state of well being/thermal modeling. Listed below are some examples of that course of movement at Lucid:
Parameter measurements: As soon as consultant cells can be found from the producer, an intensive suite of cell testing and information processing is kicked off for Equal Circuit Modeling (ECM) improvement. The cell parameter datasets obtained from testing are important for correct state of cost (SoC) and state of well being (SoH) estimation.
Variability research: From the method functionality facet, it’s important to trace cell-to-cell variability by means of design validation, course of validation and closing mass manufacturing phases. This helps automobile techniques modeling, integration and product groups gauge the estimated vary and efficiency for the ultimate product. It’s additionally essential to characterize nominal capability and power distributions after analyzing consultant drive profiles with discharge/regeneration pulses integrated inside testing intervals. Utilizing precise cell testing information, we will get insights into establishing management limits, and hint how the gaussian power distributions would scale up at pack degree when cells are distributed in collection and parallel connections.
Optimization: Miles charged per minute defines quick cost capabilities. Complete testing is finished at cell, module and pack ranges to grasp the failure modes and lithium plating thresholds over the cell lifetime. This facilitates the choice of quick cost profiles and helps push the efficiency boundaries.
Modeling: State of well being (SoH) for lithium-ion batteries must be predicted precisely for software program controls and for prolonging cell usable lifetime. Physics-based cyclic and calendar getting old capability decay fashions are developed to seize lack of constructive/damaging electrode materials and lithium stock over battery utilization.
Charged: What are some widespread misconceptions about defining cell specs for automotive utilization eventualities?
Maithri Venkat: Cell engineering specification sheets are extraordinarily conservative in sure instances. For example, laboratory cell biking with 1C cost and 1C discharge may set off sudden degradation modes like lithium plating and gasoline technology. Within the case of the Lucid Air Dream Vary version, the automobile’s vary is 520 miles at prime of cost, and 1C discharge would imply depleting 520 miles in a single hour. That is an not possible situation in the actual world, even when we assume the bottom efficiencies throughout discharge. Cells are way more succesful once we conduct experiments underneath the vary of situations accessible to a buyer. It’s due to this fact essential to contemplate that testing underneath the suitable situations can assist entry extra consultant limits of efficiency boundaries. As an analogy, Olympic groups don’t choose their marathon runners based mostly on their efficiency in a 100-meter sprint!
Moreover, sure provider specification sheets are based mostly on client electronics, for which power estimations are calculated with extraordinarily low constant-voltage cutoffs on the finish of charging classes, or cells are cycled constantly between zero and 100% state of cost. Customers of EVs hardly ever cost to 100% after which drive right down to zero. Consequently, it doesn’t all the time make sense to carry out testing and specification setting with such utilization patterns.
Charged: How can automotive firms assist cell suppliers develop specs?
Maithri Venkat: We should always make sure that provider specification sheets match automotive use instances. I acknowledge that it’s difficult to specify a precise automotive use case. Nevertheless, it could nonetheless be useful to rewrite the specs to evolve extra intently to what prospects would possibly expertise.
At Lucid, battery information scientists use fleet telemetry information to grasp life like utilization profiles. Quick cost efficiency boundaries are evaluated based mostly on the popular charger kind, temperature regimes and state of cost (SoC) for session starting and finish. Automotive firms can train cell suppliers so much which will return into their improvement processes and assist them make a greater product.
Subsequently, it could be useful to have steady communication between cell producers and OEMs for incorporating client utilization profiles in engineering specs.
Lastly, it could be useful for automotive firms to drive specs improvement. Finally, this serves the very best pursuits of each cell suppliers and OEMs.
Charged: You talked about life like profiles earlier. How will we incorporate real-world getting old into laboratory testing? Is there a strategy to strike a steadiness between utilizing aggressive getting old vs life like getting old profiles for cell evaluations?
Maithri Venkat: It’s of paramount significance to grasp the tradeoffs related to utilizing aggressive vs life like getting old profiles previous to figuring out the design of experiments for laboratory cell assessments. Testing strategies involving slower cost/discharge, decreased depth of discharge and common temperatures could be splendid for replicating typical EV utilization. Below these situations, lithium-ion batteries would expertise the degradation mechanisms equivalent to stable electrolyte interphase (SEI) progress which are noticed in real-world driving. Nevertheless, this could additionally suggest for much longer check timelines to acquire capability loss and resistance progress information.
Alternatively, utilizing accelerated getting old may lead to lithium plating on the anode as a result of diffusion limitations or gasoline technology from electrolyte solvent discount reactions. Whereas the testing time is decreased, the failure modes will not be consultant and even achievable for these nook instances.
Ideally, one wants to decide on intermediate cost/discharge charges with relaxation steps integrated between cycles for efficient efficiency scale-up.
Charged: What are the cell pattern portions vital for every developmental section?
Maithri Venkat: Cell pattern dimension required will enhance by means of the developmental phases. For provider analysis and cell design screening, it could possibly be enough to begin with a whole lot of early R&D pattern cells. Nevertheless, as soon as the design is confirmed, efficiency optimization and sturdiness testing would require 1000’s of cell samples. After this, we get into module and pack testing. The cell amount required for that is 10 instances extra in comparison with the earlier section. Subsequently, the ultimate automobile testing section would require over 100 instances extra from the mass manufacturing line in comparison with preliminary R&D evaluations. It is very important keep in mind that bigger portions for cell allocations should be obtainable far upfront of the beginning of car manufacturing.
Charged: Why are consultant battery packs required for automobile testing months upfront of the beginning of manufacturing?
Maithri Venkat: That is associated to the kind of automobile validation and regulatory checks being performed. Having an early begin to validation helps offset longer lead instances related to testing and information procurement. Examples embrace automobile fleet deployment, scorching/chilly climate local weather testing, homologation and SoC/SoH software program algorithm validation. Electrical automobiles have to undergo mileage accumulation and standardized sturdiness testing to make sure constant long-term efficiency, reliability and guarantee assurance.
Charged: Finally, the objective is to get cells into automobiles. What can be a few of the key duties that we have to observe whereas transferring in the direction of manufacturing scale-up throughout EV manufacturing?
Maithri Venkat: Even after finishing efficiency optimization and reliability assessments, we nonetheless should be aware of recent product introduction within the manufacturing unit. As we transfer in the direction of manufacturing ramp-up, we have to think about cell integration into modules and packs on the manufacturing stage. Every cell kind must have a definite manufacturing half quantity, gear settings, and even information dealing with. Even mundane modifications like barcode placement on a cell field can dramatically affect yield if course of controls will not be completely optimized.
One other instance is the implementation of totally automated in-line inspection strategies for checking key cell traits. These high-speed measurements, together with mid-process and end-of-line measurements, assist us make sure that the processes concerned in constructing modules and packs haven’t impacted the integrity or efficiency of our cells.
Charged: What concerning the general timing? How a lot time will we usually have to qualify a cell for automotive utilization?
Maithri Venkat: Cell improvement for automotive functions occurs years upfront. Since each cell has distinctive traits, it’s important to conduct detailed testing all through the qualification phases to probe into cell degradation mechanisms and consider efficiency thresholds.
We would wish to guage the event timeline on a person foundation. The time required can be depending on necessities, know-how readiness, cell chemistry, manufacturing feasibility, and the supposed EV utility and market. Talking typically, it’s a few years.
Let’s additionally think about a situation wherein the cell chemistry is frozen, and there’s a change with respect to a minor course of throughout manufacturing. Whereas this would possibly create a major enchancment in yield, the staff nonetheless wants to guage if it has an affect on efficiency or security. For this instance, it’s potential that a complete re-qualification of the cell will not be required, and the change could be rapidly accredited. Nevertheless, it’s also potential that even an earthly course of change from a cell producer may have unintended but extreme impacts downstream for an automotive maker. Subsequently, each single change to a cell must be scrutinized. I wish to spotlight that each cell is exclusive. Qualification methods and developmental timelines should be evaluated on a case-by-case foundation. Battery cells could be some of the vital path gadgets in your EV improvement.
This text first appeared in Difficulty 66: October-December 2023 – Subscribe now.