Details On Audi’s Battery Technology

2 years ago by Mark Kane 21

Audi lithium-ion battery

Audi lithium-ion battery

Audi A3 Sportback e-tron battery

Audi A3 Sportback e-tron battery

Audi recently presented its lithium-ion battery approach for plug-in electric cars.

The German manufacturer works on batteries at the competence center for high-voltage battery technology in Gaimersheim, Germany.

According to Audi, their expertise spans beyond cell development, and includes pack management, arranging cells into modules, etc.

Audi, together with Volkswagen and Porsche, as a large automotive group, is developing and producing batteries under a uniform modular concept to use in various models and brands.

The base element – modules – can consist of one of three types of cells (round cells, prismatic cells or long, flat pouch cells). Each type has its own advantages and disadvantages. The first one, used by Tesla and by Audi in the latest R8 e-tron, stores a lot of energy, but the power output is limited for example.

Audi R8 e-tron

Audi R8 e-tron

The module as central factor
The decisive factor for Audi is the battery module – a sturdy cuboid aluminum housing slightly smaller than a shoe box. The module weighs around 13 kilograms (28.7 lb) and within the battery system is mounted on a cooling plate through which cooling fluid circulates. It can accommodate three types of cell: round cells such as those used in the R8 e‑tron 2.0*, prismatic cells – each of them about half the size of a paperback book – or long, flat pouch cells.

The prismatic cells have separate aluminum housings, so they are more robust than pouch cells. Their outer skin is made from aluminum-coated polymer and this in turn brings weight advantages. In terms of the performance of the battery system, the individual strengths and weaknesses of both concepts cancel each other out. The two suppliers with which Audi works have each specialized in a particular design.

The strength that prismatic and pouch cells have in common is the dense packaging. They both use 75 percent of the available volume, a much higher figure than round cells (50 percent), which also require more complex contacting.

Round cells are generally only suitable for all-electric vehicles; while they store a high amount of energy compared to the other designs, their power output is comparatively low.

Audi e-tron quattro concept - Electric drivetrain with up to 370 kW

Audi e-tron quattro concept – Electric drivetrain with up to 370 kW

Pouch cells and prismatic cells are more versatile. With minor changes to their exterior dimensions, they can be configured specifically for maximum power output, maximum energy or a combination of both, making them ideal for a plug-in hybrid vehicle. The key criterion is the coating thickness of the electrodes – the thinner these are, the greater the contact surface between electrolyte and active material; the resulting high charge transfer assures a corresponding performance density. Conversely, high coating thicknesses for the electrodes produce a high energy density.

Worldwide, the development of lithium-ion battery technology is advancing very rapidly. Over the past three years Audi has succeeded in increasing the current capacity­ of prismatic cells by 50 percent – from 25 ampere hours per cell to 37 Ah. Energy density has increased by a similar degree. Pouch cells now achieve up to 550 watt hours per liter of volume, and Audi expects them to reach about 750 Wh/l by 2025. An important incidental effect is that battery costs have fallen by around half in the past five years. That is making electric mobility affordable for more and more customers.

Development in the competence center
Audi is helping to push forward developments with meticulous attention to detail. Together with Volkswagen Group Research, the brand with the four rings is also getting involved in long-term projects that are investigating innovative cell chemistry. At the special high-voltage competence center near Ingolstadt, the focus is on the development of complete systems: packaging, cooling, validation and, in partnership with body development, integration into the automobile. It is above all working on the battery system’s rigidity and its behavior in a crash situation – Audi is testing loads at up to 150 times the force of gravity.

Design is opening up interesting fresh scope specifically for future electric cars. Audi gave a foretaste of this at the 2015 Frankfurt Motor Show. In the Audi e‑tron quattro concept, the 95 kWh battery takes the form of a large, flat block beneath the passenger compartment, ideally positioned in terms of center of gravity between the axles. There is no longer a center tunnel in the body. This model points the way forward – as a precursor of the all-electric-drive sport SUV from Audi.”

Audi Q7 e-tron 2.0 TFSI quattro (offer on the Chinese market)

Audi Q7 e-tron 2.0 TFSI quattro battery

Audi hopes that lithium-ion batteries will last for at least 150,000 km (nearly 100,000 miles) and 8 years, before any significant capacity drop will be detected.

Those cars still could work just fine or, if the capacity drop is  too high for the owner, could be used as energy storage system.

Developments of ESS is already underway:

“New lease of life for used batteries
Audi designs its batteries for high service lives of more than 150,000 kilometers (93,205.7 miles) and at least eight years in operation. Even then, these batteries still possess a large portion of their nominal capacity – too high for them to be recycled. Under a venture with the motto “From Road to Grid”, the Company is therefore currently working on a concept to convert old batteries into stationary energy stores.

A first test setup located near Ingolstadt recently started supplying the grid. A container for four traction batteries of various sizes works in tandem with a photovoltaic system that is capable of supplying up to 20 kW of power on sunny days. A second container houses the connection and control technology: Its power electronics convert the direct current from the batteries into alternating current at a standard voltage of 400 V. When the batteries have been run down to ten percent of their capacity, they are sent for recycling.

Audi’s innovative storage platforms are suitable as a power source for quick-charging stations with an output of more than 250 kW. Alternatively they can serve as buffers for renewables such as wind and solar power – whether as part of the grid or as home installations. Audi has already drawn up plans for larger systems with a capacity of around 500 kWh.”

Tags: , ,

21 responses to "Details On Audi’s Battery Technology"

  1. jerryd says:

    I’d dispute round cells can’t put out high specific power but otherwise a good
    piece.
    A cuboid isn’t a great shape in any high range EV as a floor battery is about mandatory to get over 100mile
    range.
    While modules, electronics can be common the pack shape will be dictated by the vehicle
    design.
    Smart would having 2-3 size of floor battery/suspension chassis and then build off of them is how they will end up so why not start that way?

    1. Three Electrics says:

      They detail a cuboid design above that stores 95 kWh. What is the basis for your claim that a floor battery is required? Is it because Tesla went that route?

      1. Three Electrics says:

        Sorry, that battery looks to be for their hybrids. Their 95 kWh battery looks floor.

      2. Pushmi-Pullyu says:

        Three Electrics

        “What is the basis for your claim that a floor battery is required?”

        I don’t think he was claiming that the battery pack being in a flat layer below the floor is “required”; it’s merely the most practical placement. It allows a flat floor in the passenger compartment. Otherwise, you get something like the hump in the Volt’s floor; a hump which makes the middle seating position in the back seat impractical for seating adults.

        The Tesla Model S, the BMW i3, and I think the GM Bolt all place their battery packs in a flat layer below the floor. Looking forward to the future, I think we can expect this to be the typical placement for most or all EVs with large battery packs. Or at least, most or all EVs which are properly designed from the ground up… and not just gasmobiles with electric powertrains shoehorned into them.

        1. The Leaf battery makes good use of space too as a combo of under the seats and rear floor pan. It leaves a nice deep cargo compartment. In some regards it makes more sense than a flat skateboard since the space under the seats is otherwise wasted.

          1. JakeY says:

            Tesla puts their onboard charger there so that space is used up already.

          2. chris says:

            Th way I read it, the 95 kWh battery is skateboard design between the axles. But anyone know if e-tron Quattro SUV (BEV) will have prismatic cells?)

            The r8e is basically the closest thing to a tesla s imho. (18650 cells in skateboard form factor)

      3. jerryd says:

        Because Floor is the only way without talking up passenger, storage room.
        It also gives a great CG both low and centered, 4” lower than any gas car.
        If in front, back it creates polar moment that hurts handling.

    2. DanCar says:

      Yes round cells, 18650, don’t have a power issue. The issue is that there is cost savings to be had with larger cells.

    3. Pushmi-Pullyu says:

      jerryd said:

      “I’d dispute round cells can’t put out high specific power…”

      Right. That will depend on the internal design and construction of the cell, not on form factor.

      For example, this website claims to sell “high discharge rate” 18650 cells:

      https://www.powerstream.com/18650-high-discharge-rate.htm

      The fact that Tesla cars need high energy density cells rather than high power cells follows naturally from Tesla using thousands of cells in a battery pack. When you’ve got that many cells which are all providing power at once, you don’t need each cell to put out that much power. EVs using battery packs with significantly fewer cells — and nearly all non-Tesla EVs use far fewer cells — will need much higher power output per cell.

      1. Ambulator says:

        Maybe this has something to do with the German’s weird obsession with amp hours. The proper measure is watt hours (Wh).

        Amp hours were sort of ok when everyone was dealing with 12 volt batteries, but it is now meaningless by itself.

        1. Bill Howland says:

          Weird obsession? Neither figure is complete.

          As far as 12 volt batteries are concerned – I’d prefer the old ’20 – hr ah’ to ‘reserve cap’ and ‘cca’ – which combine a few details but don’t give capacity info as the old system did.

          It is getting almost impossible to post here. And I use CC and Malwarebytes all the time. It is simply too resource intensive.

  2. Three Electrics says:

    Audi mentions improvements they’ve made over the past three years. How long have they been investing in battery technology? Before 2012?

    1. Pushmi-Pullyu says:

      The PR copy has a lot of tech buzz words apparently intended to impress the reader, but note that most of the statements are about form factor and the physical arrangement of the battery pack.

      For example: “The prismatic cells have separate aluminum housings, so they are more robust than pouch cells.” Seriously, we’re supposed to be impressed because they’re using cells which have a rigid housing, rather than using pouch cells which need to be installed in a frame for support? That doesn’t impress me at all; it’s merely a different form factor. That “separate aluminum housing” for each cell will be more expensive, too.

      I’d be far more impressed if they were talking about what’s actually important: Battery cell chemistry and cost. The fact that they don’t mention these things is a red flag; looks like they’re desperately playing catch-up.

      Tesla doesn’t brag about how well the internal structure of its battery pack is laid out. It doesn’t need to.

      1. Pajda says:

        I do not think that this press release is completely useless . Audi explaining two important things. The first is that still the most energy dense cells are in 18650 cylindrical size. And even if you can use only about 50% of available installation space with them, you still get significantly better overall energy density than with todays best big prismatic or pouch cells.

        And the second thing is that you do not need to much care about gravimetric density of used cells if you want to make a long range BEV. Volumetric density and battery pack space optimization is the real problem for next ca 10 years until we reach at least the 1000 Wh/l at cell level in 18650 size or 750Wh/l in pouch cells. Only after that makes sense to seriously start thinking about improving of gravimetric density of used cells.

  3. SJC says:

    R8e has been written about for years. Mercedes already has their SLS EV so where is the R8e?

  4. Stephen Hodges says:

    I like the idea of using the used battery packs in fast chargers, I would guess you then don’t need such a large connection to the grid.

    1. SJC says:

      That is the idea, you may have 12 fast chargers and three are out of service being charged, but the others are in service.

  5. Bill Howland says:

    At least they are planning a 500 kwh battery.

    1. przemo_li says:

      It would give car with 1000 miles range. Complete waste of space/cash. Cause You will mąkę multiple stops near fast chargers anyway….

      1. Bill Howland says:

        Well it must be a large car if it will only go 1000 miles. But taking your numbers, I would go from BUffalo to Chicago (around 600 miles), and then stop at some 30 amp level 2 charger while in Chicago for 8 hours to give me the few extra miles I need to get back home. If its close I’d slow down a bit to make the juice last.

        But I’m not so concerned about fast chargers since there will be none along the routes I normally drive for years to come, therefore, I don’t even plan on using anything but small level 2 public chargers.

        Unlike California, we don’t have many charging facilities OF ANY KIND at all. Therefore, I have to adjust my plans to compensate for it, and if a 500 kwh battery were reasonably low-cost, I’d buy one.

        I don’t categorize it as a waste, since I traditionally have used ALL the battery capacity often of the 3 ev’s I’ve owned to date. Even though it is only listed as 35 mile range, I at LEAST once a week get 50-51 miles out of a commute with my ELR and the vast majority of time I can fully complete the commute without the engine starting. The roadster, on frequent trips to Rochester and Syracuse – I’ve come back home fearful of running out until I could hit the local Nissan dealer’s 6 kw facilities to charge for only 10 minutes to make it another 3 miles to home.

        So If I had a car with a 500 kwh battery, I’d use it.

        Far more usuable than upper-middle class types who always have automatic GUARDIAN generators (such as the original founder of INSIDEEVS has – Lyle Dennis??) who have all that ‘Useless wasteful infrastructure’ installed at their upscale homes, and have to weekly run, be heated in the winter time, and have all kinds of maintenance so they will run on the unlikely occurrence of a utility failure.

        I get much more useability out of large batteries, (and also, for trips – I get great functionality out of that ‘ wasteful’ gas engine in my Volt and ELR – far more ecoonomic than Automatic Backup Generators which almost all rich people have.

        Now me? I spent $390 Nine years ago for a 5 kw backup generator, which I’ve changed the oil twice, and cleaned the carburetor once to keep it as good as new. So my ‘insurance policy’ is a VERY TINY amount of money well spent.

        My former house I rent out, with the garage wired similiarly to my current house, so if my Tenant at my old house needs backup power, the generator gets loaded into the hatchback Volt and off it goes to my Tenant.

        So , it is providing backup insurance to TWO totally separate properties.