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Continental Begins Series Production of Lithium-ion Battery Packs for Hybrid Vehicles

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The battery which Continental has developed for the Mercedes-Benz hybrid weighs around 25 kilograms and requires an installation volume of some 13 liters. Click to enlarge.

Continental has begun series production of lithium-ion battery packs to be used in hybrid-electric cars. The initial packs produced at Continental’s plant in Nuremberg, Germany, will be installed as standard in the new Mercedes S400 BlueHYBRID, available from the middle of 2009. (Earlier post.) The 120V battery-powered electric motor in the Mercedes hybrid can boost the combustion engine by up to 19 kW.

The Continental battery pack, with cells from Johnson Controls-Saft (earlier post), weighs around 25 kg (55 lbs) and requires an installation volume of some 13 liters (0.46 cubic foot).

Continental’s Powertrain Division invested more than €3 million (US$4.4 million) in building up manufacturing capacity at the Nuremberg site. The company held a joint celebration this Wednesday in Nuremberg together with customers, suppliers and political and media representatives to mark the start of series production.

Continental’s battery management system (BMS) monitors the battery so that it is always within the optimum working range. The electronics compare the battery’s overall condition, temperature and energy reserves against its age; safety circuits prevent the energy storage unit from becoming too hot. A Cell Supervision Circuit (CSC) monitors the individual cells and ensures their optimum interaction.

The CSC balances the charge levels of all the cells in the battery to prevent cells from being permanently subjected to uneven loads. This helps to ensure that the lithium-ion batteries will really last—with unimpaired functionality, power and safety—for the required ten years or 160,000 to 240,000 kilometers. Batteries produced since last year as part of the pre-production series have been artificially aged in testing to simulate their use in vehicles over time.

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A resistance welding process joins the copper bus bars. Click to enlarge.

Since the current inside the battery is not conducted via cables but along copper bus bars, a special welding resistance welding process (using 16,000 amps) is used to join the bus bars so that the current can then flow unimpeded past the welding seams and avoid power losses. The lithium-ion batteries are fully enclosed in a laser-welded, stainless steel housing.

Continental says that it, together with its waste disposal partners, is developing recycling ideas which will allow at least 50% of the content of lithium-ion cells to be recycled.

Continental started pre-series production of lithium-ion batteries last year in Berlin. The Nuremberg site, which was prepared for series production in 12 months, can produce 15,000 lithium-ion battery packs annually—this capacity can be doubled at short notice, according to the company.

Comments

TM

Only 15,000 units per year? OK - 30,000?
Sounds like they are not convinced this will be a big seller.

Will S

Ok, so what's the kWhr capacity at various loads? How much are they going to sell for? What's their DoD cycle chart look like? Max amps?

clett

It's not just Mercedes that have been sniffing around Continental for their (small pack size) lithium-ion. Expect other announcements soon....

Hal

What does the adjective "series" mean in the phrase "series production"? Is that some translation of commonly used German manufacturing phraseology?

sjc

"pre-series production..." might have been better phrases pre-production series or as some operations people refer to as "post pilot run". You have prototypes, pilot runs, post pilot runs, and pre-production runs. It is a fancy way of saying we are increasing production volumes gradually with every "batch", so that we do not screw up big time and cost the company a ton of money, embarrass ourselves and lose our jobs.

philm

Western industry trumps the big production capacity of the East????

HarveyD

The Ford Model T was produced in series or in linear production lines.

Latter on it was called mass production.

A few years latter it became automated series/mass production lines.

One may assume that series production lines are close to or the same as mass production lines, may they be automated or not.

Of course, that type of production lines can be accellerated or expanded 24/7 or multiplied as required.

China's BYD new expandable 1 M sqaure meter battery plant may eventually have a multitude of assembly lines and produce enough battery packs for over one million PHEV and/or BEV a year.

arnold

Now we just need a seamless laser unwelding machine (or angle grinder) to get back in to remove replace that dodgey cell.
But I forget in this throw away world everyone has unlimited credit (Mercedes et al.) and is far too silly to ever be allowed inside a black box.
Oh well it give the grumpy old men new purpose.
Otherwise, Very nice.

Andrew

To work in the Mercedes the battery needs to provide up to 19KW of motor power.

Just a guess, but if the battery is specified to draw current at max 8C you would have a ~2.4 KWh battery. Sounds about right for a 25Kg box.

Sweet looking package that might work well for EV conversions. Though I'm not holding my breath.

Herm

replacing a single cell in a stack is kind of hard, as the cells age they change and thus the pack will need frequent rebalancing. It can be done but it can also be a pain in the neck. You may actually want to replace it with an artificially aged cell.

Also, it sounds like they are using the flammable type of lithium cells (not A123 LIFE cells as an example), thus they need that laser welding on the case.

P Schager

I understood that JCS-Saft was going to go with liquid cooling, or at least immersing the cells in a liquid, for safety. That could account for the welded-shut case. Unfortunate to not be able to replace cells, though. (Their CSC circuit should surely take care of the age-mismatched replacement cell problem.) You won't know for certain that the battery lasts 10 years until 10 years are up, and this is a major impediment to the rapid shift to electrification. Cell reliability issues that show up with aging are always a possibility, in some minds if not in those of the engineers.

I hope the 50% of the cells they're working on recycling is the lithium, cobalt and nickel (which matter) and not the graphite, polymers and metal case (which don't).

Anne

@Herm:

Read the article better. Manual rebalancing is a thing of the past:

The CSC balances the charge levels of all the cells in the battery to prevent cells from being permanently subjected to uneven loads.

@arnold:

Right about the throw away society, but if it gets recycled properly, that doesn't need to be a big problem. And thanks to the CSC (see quote above), replacing a single dodgy cell should be a thing of the past.

The dodgy cell is usually the one that came off the production line with a slightly lower capacity. As it is subjected to lower DoD's than the other ones, it ages faster, worsening the imbalance. The CSC should take care of that.

arnold

Anne,
I recall seeing references to managing cell redundancy as part of string management.(cant think where) Whereby a failure in part of that battery could be isolated and the battery had enough cells so that a certain redundancy was tolerated.
Think: Bakers dozen 13. Other marginal ordering principles, Stock inventory.
Safety margin of *5 except where personal protection requires *10.

If the stack can fail, we could ask what mode? Is it possible to build in a limp home(if required) What is the cost of possible repair or redundancy strategies?
What is the cost of replacing the stack and the time down for servicing where given available funds, a delay from o'seas order,delivery, replacement vehicle?
This is all too common in the real world and sometimes businesses go to the wall waiting.

Many mechanics, who are more interested in the manual art and less qualified in chequebook mechaniking will describe the frustration and consequential issues surrounding breakdowns.

The companies that go that bit further in this respect gain the loyalty and recommendation of the techs. (who should? know)

Andrew

I have been educatin' on BMS systems.

It's possible to have a cheap solid state switch in parallel with every battery in a series string. That switch can be instructed to bypass curent around a defective battery. (Can also be used to balance the string)

When an individual battery fails, the overall pack voltage will drop. The energy storage capacity will also drop. The battery voltage and energy storage capacity can be designed with margin for the expected failure rate.

They have developed an accelerated life test to estimate the future failure rate. This little tidbit of news should not pass unnoticed. It is notoriously difficult to artificially age products. There could be an error of margin of several years.

A lot of potential customers are adopting a wait and see approach (See if the battery will really last 10 years). If Li-ion battery ageing can be modelled successfully, it will allay some market acceptance fears. The biggest benefit is we will see an acceleration in time to market for new chemistry.

Chris

Who is manufacturing the cells for Conti?

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