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The electric logbook
The ADAC blog on electromobility and alternative drives
Battery expert Sven Bauer: “The Tesla battery or the
one in the BMW i3 – they’re miles apart”
Published on 21 October 2013
Sven Bauer, CEO of Europe’s largest battery manufacturer, knows about the latest lithium-
ion technology better than anyone else.
In this interview, he explains how the business has changed in recent years and how the
battery inside a Tesla Model S differs from the battery inside a BMW i3.
Sven Bauer’s company BMZ produces batteries in Europe, China and the USA. Now
also for the German company Streetscooter GmbH
Mr Bauer, we spoke for the first time about lithium-ion batteries two and a half years ago.
How has the business developed since then?
Brilliantly. Last year, we were Germany’s best company and this year, 2013, one of the best 50 in
the world. This is down to the fact that we work in all directions, not just for battery-powered
screwdrivers, garden equipment, etc., and thus continue to develop. At the moment, the compact
vehicles sector is booming, i.e. bikes and scooters, not to mention the industrial vehicles sector,
e.g. road sweepers, forklifts, post vans. Companies that use vehicles every day from morning to
evening are moving away from the internal-combustion engine and switching to electric drives.
It’s worthwhile for them. We are currently conducting a project to promote electric drives and are
converting taxis to run on lithium-ion batteries. It’s exactly the same for the business with
industrial trucks. The market is gigantic.
How has your turnover developed in figures?
We have trebled our turnover over the last five years.
Are the cells that you use for making batteries still the same as two or three years ago?
No, that has changed completely. Particularly with regard to the cells for cars. Tesla for instance
still uses the 18650, a 2.9 or rather a 3.4 Ah cell more recently. That is the round cell everyone
knows from electrical devices in the home. With a nickel-cobalt-aluminium cathode and graphite
on the anode and mixed with a bit of silicon. The battery life is not very long in this case. Renault
uses an NCM pouch cell. This is a better option. Pouch cells are flat and have aluminium foil as an
outer skin. The drawback is that they eventually swell up, which limits their service life. The cells
used in the BMW i3 are state of the art. A nickel-cobalt-manganese cell with a solid core. This
means with a solid aluminium housing, which is laser-welded. It is designed to last 20 years.
20 years? How can you know this for sure?
It is possible to run simulations in series of tests.
Is the service life forecast reliable?
It is very reliable. It is possible to prove this to within exactly a month. Putting it precisely, the
battery life is 20.9 years. End of life means that the battery can still be charged up to 80 percent of
its original capacity.
In our first discussion, you mentioned a price of around 250 euros per kilowatt hour. What
is the price today?
You can’t compare this price any longer, since this was the price for the 18650 cells, whose life is
shorter and which require greater effort in terms of their production, i.e. bringing together and
managing this great number of cells.
Large-volume cells with 20 years’ service life such as those in the BMW i3 offer significantly
higher performance, but are currently more expensive in terms of watt-hours. Significantly less
effort is required however for the battery management. We are now also talking about prices of
between 250 to 300 euros per kilowatt hour, but for considerably higher performance and a
Do you still mainly produce small batteries?
No, we have seen a shift there. The batteries are getting bigger. We have now produced the first
50 batteries for the largest electric fleet in Europe, namely the fleet of the German Post Office (the
Streetscooter, editor’s note). This number is set to grow to 8000 vehicles next year. We will
shortly be producing the batteries for the next 2000 vehicles. Industrial vehicles such as road
sweepers, forklifts and excavators constitute the largest volume.
Let us come back to the Tesla mentioned earlier, whose ranges are impressive. Why are
other carmakers unable to achieve such ranges? Is this down to the cell or the overall
The ranges are so good, because Tesla installs very large battery packs in the vehicle. But with a
18650 cell, they are never going to achieve 20 years’ battery life.
What life do you think the Tesla batteries are realistically capable of achieving?
If the battery is looked after carefully, perhaps eight years tops. If you regularly drive flat out or
live in a hot region such as California, where the road can reach temperatures of 60, 70 degrees,
then perhaps only four or five years.
In other words, it’s wrong to believe that Tesla has better batteries?
First off, Tesla has a battery that works. But in comparison with this, the battery in the BMW i3 is
a quantum leap. BMW has an industrially produced, advanced battery with cells specifically
tailored for the job, as opposed to a laptop cell that has been modified for an automotive
application. They’re miles apart.
Tesla will have a problem, because customers will hardly be prepared – after only five or six years
– to fork out around 20,000 euros for a new battery.
Do you have an explanation for what might have caused the battery to catch fire in the
Tesla Model S in the USA?
No, not really. Apparently, the most unlikely of all scenarios happened. Tesla’s battery is very
solidly built and equipped with all modern safety technologies. If a module gets damaged in the
battery pack, it is then automatically electrically cut off from all the other modules. It’s a bit like
with the Titanic, the unsinkable ship with lots of air chambers. However, so many of these air
chambers were ruptured that the Titanic did in fact sink. Nevertheless, as to how a metal object
that is simply lying on the road and gets run over can destroy the sturdy casing on the Tesla
battery is a mystery to me. Not even a wrench could do this damage.
Have the cell manufacturers given you any indication that they will be starting large-scale
production with entirely new cell chemistry in the foreseeable future?
No, that’s all still very much up in the air. Almost all manufacturers of cells for the automotive
industry are experiencing a rough ride. None of them are making any profit. Many of them have
already ceased production, take for example Johnson Controls and Continental. Those
responsible at Sony have decided to stall production of automotive cells, because the market is
currently not ready. LG’s production for the Opel Ampera and the Chevrolet Volt is running at
only 10% capacity. The investment has been a disaster. Samsung is only now starting to produce,
having invested between three and four billion euros and is hoping that the BMW i3 will be a hit.
BMW will no doubt also be hoping this…
Yes, of course.
You told that you were planning to install an energy storage system in your own home for
the solar panels on the roof in order to become energy self-sufficient. How far have you
got with this?
A month ago, the Federal Government gave us the official go-ahead to develop the ‘Second Life’ of
the battery, and to do this we are receiving funding of just under ten million euros in an alliance
with other companies from the automotive and storage sector. I am naturally totally thrilled about
this. We are developing a controller that sits on the cell and records the history, so that we know
exactly what is wrong with the cell and how it has been used. Once the battery has reached its
residual capacity of 80 or 70%, you then remove it from the car, take it into the house and connect
to the smart grid. It can be used as a storage system for the home.
Won’t you need a large cellar for this?
No, not at all. We are talking about 5.2 kilowatt hours per person, which is consumed in the
home. For four persons, this means 20 kilowatt hours. A storage system such as this is only about
the size of a dishwasher.
And you’ve already got such a system at home?
Not yet, unfortunately. This is because I want to do it right from the start, namely so that we can
feed in electricity bidirectionally. Into the energy storage system and into the grid. This takes a
little while longer to coordinate with the electricity supplier. But what we definitively have is that
from 1 May 2014 you receive 30% funding from the government for putting a battery in your
cellar. We anticipate that this market will be many times larger than the entire automotive
Sounds very promising …
Yes, it’s fantastic. Everyone who owns an electric car can offset some of the expense. If the battery
in the car no longer charges up sufficiently, I then simply use it in the home. There is no disposal
problem. Drivers of electric cars have a very inexpensive energy storage system and can supply
themselves independently to a small extent.
And for how long can the battery continue to be used until it’s no longer fit for this
As the company BMZ, we must guarantee twelve years additional life in the battery’s ‘Second
Life’. That is the basis.
Does this mean that the batteries you eventually get back from the post vans then end up
in the cellar?
Exactly. Although this will take another six, seven or even eight years before post van batteries
can be used as ‘Second Life’ storage systems, I am very excited about the whole idea. I definitely
want to try it out for myself.