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Design of the Daimler S400 Mild Hybrid System

S400A
Hybrid concept for the S 400 hybrid. Source: Daimler. Click to enlarge.

Daimler’s S400 BlueHYBRID, which goes on sale this month, is the first series production passenger car featuring a traction lithium-ion battery pack. (Earlier post.) At the Advanced Automotive Battery Conference 2009 in Long Beach, Dr. Uwe Wiedemann from Mercedes-Benz Cars/Development, Hybrid Systems & Components, presented an overview of the design of the system and components, with a particular emphasis on managing the small 0.8 kWh Li-ion pack.

The S400 Hybrid uses a parallel mild hybrid system with a small 15 kW e-motor connected to the crankshaft between the motor and transmission, along with a Lithium-ion battery pack for energy storage, power electronics and a complement of electrified auximilary systems. The system offers start/stop functions, regnerative braking and electrical drive support.

Although the motor seems small from a power output perspective, “for the given architecture it turned out that the maximum fuel reduction occurred at electrification of 15-16 kW. That’s why we chose a lower system,” Wiedemann said.

S400B
Combined torque curve for the S400 hybrid. Click to enlarge.

The high torque of the e-motor at low speeds offsets the reduction in low-end torque resulting from applying the Atkinson cycle to the combustion engine.

Moving to a more powerful e-motor increased the weight of the hybrid system and decreased the fuel consumption. Furthermore, at a higher electrical to combustion power ratio, the e-motor operates increasingly in less favorable areas of the performance map as maximum requirements increase. Although relatively low in power, the e-motor delivers rated torque of 160 N·m (118 lb-ft), contributing to a combined system torque of 385 N·m (284 lb-ft).

Power electronics. The power electronics—from Continental—comprise a control unit which acts as the master of the E-drive system and a power unit that converts the direct current generated by the battery. The power electronics can cope with continuous currents of 150A, and short-term as high as 310A. Power is supplied to the e-motor by a bus bar.

The power electronics are situated in the engine compartment in the location of the conventional starter motor and are cooled by a separate circuit.

S400lib
The S400 hybrid battery pack. Click to enlarge.

Lithium-ion battery pack. The compact Li-ion pack, developed by Continental and JCS Saft, comprises 35 cells and provides 19 kW of power, with a capacity of 6.5 Ah. The battery is connected to the vehicle air conditioning circuit so it can be cooled independent from the engine.

Cut-off valves are integrated into the system that allows the customer to switchoff the air conditioning without interrupting battery cooling. When the engine is not running, the electric A/C compressor not only provides air conditioning but also guarantees that the battery’s operating temperature limits are not exceeded. Battery pack temperatures do not increased above 50 °C in any operating state to prevent serious damage.

Operating strategy. The operating strategy of the S400 hybrid is based around start/stop, regenerative braking, boost and load point shifting—i.e., moving the load point of the combustion engine to less consumption-intensive ranges while offsetting the torque deficit with the e-motor.

When providing support for load-point shifting, the operating strategy only allows shallow discharge cycle of the Li-ion battery to maintain the cycle strength. Fuller deployment of the electrical support is only provided based on the driver’s request, as indicated by accelerator pedal position and a large pedal value gradient.

The focus of state of charge (SOC) swings is in the range of 5%. Values of up to 10% occur less frequently, while SOC cycle of more than 10% are rarely observed. This contributes to the 10-year expected service life.

Comments

ToppaTom

We should be above responding to this conspiracy BS.

Almost by definition, belief in conspiracy theories means a certain lack of objectivity; or worse.

It has been a while since I read up on the Ovshinsky-GM-Ovonic-Texaco-Chevron NiMH battery conspiracy thing. I'll have to research this again (but this does NOT necessarily mean watching some juvenile movie).

But why is the large format become so dear to these people? Is this a new wrinkle to the conspiracy, or did I just forget it ?

kelly

"But why is the large format become so dear to these people? Is this a new wrinkle to the conspiracy, or did I just forget it ?"

You forgot a lot, like reading the comments and links.

People want an EV(or any non-polluting vehicle) costing less than an ICE vehicle per mile driven. A viable EV/battery mass-manufactured and on-the-roads for ten years could have done that. Suddenly, the Chevron oil company holds the patents and sues the successful 1997 EV-95 NiMH battery (RAV4, Honda, .. EV's) off the market. This sent a signal as clear as GM crushing the EV1.

GM earned it's fate - as have others.

A statistical sampling of information gives the meaning. If there are 'conspiracy theories', people iqnoring history and thousands of web references would most likely be in them.

SJC

Large format NiMH batteries would make PHEVs and BEVs more cost effective. The RAV4 EV and EV1 might have run on 1000s of NiMH D Cells, but it makes more engineering sense to use a smaller number of large format batteries.

IMO, Chevron really is NOT in the battery business. Cobasys was a way of LOOKING like they were in the battery business. You do not go along for years with poor performance and claim that you are good managers.

They have not licensed anyone to produce large format batteries and they do not make them for sale. It is not like people don't want them, the 100s of RAV4 EV owners would like to be able to buy the EV-95, but no one makes them any more.

BTW, there is no conspiracy theory. A conspiracy involves more than one and in this case it is just Chevron. The fact is Chevron stopped Panasonic from making large format NiMH batteries, have not licensed anyone to make them and they do not make them.

ToppaTom

In Kelly’s source http://www.sigmaxi.org/programs/prizes/chubb.ovshinsky.shtml http://web.mit.edu/invent/iow/ovshinsky.html ...

Stanford Ovshinsky Interview, Part 1, Ovshinsky (who is indeed a genius second to none, but maybe not the best businessman) in answer to this question
“ So it’s your opinion that Cobasys is preventing other people from making it [high capacity ECD batteries] for that reason”
Ovshinsky says, “Cobasys is not preventing anybody, Cobasys just needs an infusion of cash. It builds a great battery and if I’d had my way and if people in the industry had listened, I had 2 next generation batteries one under test that’s doing very well one being developed …"

I'm trying to review the more reasonable sources first.

SJC

Prior to making that statement he said that selling the interests to an oil company may not have been the best thing to do.

I would say someone got to him. Chevron may have contacted his attorney and reminded them of some legal actions that might be taken. When you are involved in business deals, you have to be careful what you say.

Repression reins supreme in the land of the free. Just look at how many people go off the record and refuse to speak because they may be fired or sued.

kelly

Cobasys is claimed near bankruptcy again, yet they collect on-going royalites from decades of NiMH battery sales world-wide, besides hundreds of other energy patents.

WalMart alone sells thousands of just the NiMH rechargable batteries daily.

Something's not right and again an oil company with controlling interest appears.

ToppaTom

SJC,
Stan Ovshinsky and I say the same thing about Cobasys – but you disagree so you say he’s lying. Paranoia.
Then you weave a “might be “ fairy tale from whole cloth about how people go off the record and refuse to speak because they may be fired or sued and naively believe Ovshinsky would stoop to such cowardice.

Kelly,
You concoct some incoherent partial story about the implausibility of royalties concurrent with bankruptcy and Wal-Mart and expect us to complete it.
No.

Conclusion:
Cobasys is not preventing anybody from making high capacity ECD batteries.
Stanford Ovshinsky himself says so.

SJC

Tom, I am not even going to look up the first quote, it is not worth it. You are a stupid jerk that should be banned from this site. All you do is shoot off your mouth.

kelly

" if I’d had my way and if people in the industry had listened, I had 2 next generation batteries one under test that’s doing very well one being developed …"

Humanity and technical progress would accept Stan's "if I’d had my way..", but what about an oil company with counter interests?

Walmart's thounsands of NiMH batteries(AAA, AA, C,..) is just one example of how widely accepted and profitable his patents/royalties must be, yet only Chevron benefits if Cobasys fails.

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