Mercedes-Benz S400 Hybrid Auto Show Pics

Interesting. 6.5Ah @ 126V, that is just little more than half the capacity the Prius traction battery has. This is not so much for a car of that size. I would like to know how much benefits it really brings, or if it's more or less a "statement" (like the current GM "hybrids").

Judging from the parameters of the engine, this car is not gonna be a "fuel-sipper" by any means... If I am not mistaken, Mercedes uses very similar system to Honda's IMA, so the electric motor would only help with acceleration, but the vehicle is most likely unable to move solely on electric power. Does anybody know how much power does the electric motor have? I think I remember something like 35kW, but I may be wrong...

BTW, is this car a front or rear wheel drive? Also, I don't see a 12V battery anywhere. Does anybody know if they got rid of it completely?

 

You have to be a little careful when judging battery capacities because the capacity depends on how fast you discharge it. It's normally quoted as a 20-hour discharge rate but the label on that battery states 1hr (which means that the number is less than it would be for a 20-hour discharge rate). I'm not sure what rate the Prius battery is quoted at.

Still, 25kg isn't that much lighter than the Prius battery which is stated as 39kg. I believe that includes the steel case as well as the wiring, battery ECU and high-power relays: Panasonic EV Energy gives the module weight as 1.04kg and 28 modules comes to 29.1kg. I think Mercedes' battery is on the low side for Li-Ion energy density, but you can see that one advantage is that it's quite a bit smaller.

The S-Class is rear-wheel drive, with a longitudinally-mounted engine, so there could well be transmission continuing behind the engine, underneath the dashboard and console, and down the transmission tunnel through the centre of the car.

I'd imagine the 12V battery is under the corresponding cover on the right-hand side of the car as we're looking at it (US and continental Europe: driver's side).

Mercedes were part of the group that designed the Two-Mode transmission - basically HSD with an automatic gearbox stuck onto it - but this is an assist hybrid. Interestingly the engine is Atkinson-cycle.

Green Car Congress: Design of the Daimler S400 Mild Hybrid System

 

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Thank you very much for clarification. According the link you provided, it has only a 15kW motor - not really impressive. Anyway, it might help a little under acceleration.

The problem with this design (as well as with IMA for that matter) is that the motor is installed between the ICE and the transmission, so when doing regenerative braking, the transmission cannot shift. also, there are additional energy losses inherent to this designs, because all the moments are transferred through the gearbox.

Also, if it's a rear-wheel drive, it can only regenerate from the rear axis of the car. However, the braking balance on any car is usually set so that around 70% of the braking force is produced by the front brakes and only 30% from the rear. When braking very mildly in Prius, only the front axis could be involved, allowing for very efficient regeneration. This is not possible with rear-wheel drive, because the wast majority of the braking force must be produced by the friction brakes in the front anyway.

Overall, this hybrid system does not impress me at all...