Take a look at the most interesting questions and comments on the German Ampera Blog from the last two weeks:

Rheinhold Birgmann: Why has the generator become weaker? I can remember figures around 80 hp.

Moderator @ Rheinhold Birgmann: Nothing has changed with the performance values of the Ampera’s sophisticated and ingenious drive train. A 63 kW/86 hp 1.4-liter gasoline engine is on board to generate electricity. The four-cylinder unit is activated when the battery reaches its minimum state-of-charge and – constantly at optimum rpm – powers a generator with 54 kW/72 hp. More on this in Uwe Winter’s next post.

Yves: What kind of battery self-discharging rate (per day) needs to be reckoned with when the Ampera isn’t plugged in? How far does the Ampera’s battery management system let the battery’s residual capacity fall until it recharges the battery again?

Dr. Christian Kunstmann @ Yves: The topic of self-discharging is practically irrelevant because of the development of lithium-ion batteries. While nickel-cadmium and nickel-metal-hydride batteries have self-discharging rates of 20 to 100 percent in a month, we calculate just under one percent in general with lithium-ion technology. The Ampera’s battery is even considerably better. This effect is imperceptible to customers. So we don’t need a so-called trickle charge here. The battery is fully charged and then charging ends and it does not automatically start again.

Wolfgang: Could you please clarify: apparently the main electric motor doesn’t run at maximum rpm during high-speed driving. Does that mean that the gear ratio is changed when both e-motors are powering the car?

Uwe Winter @ Wolfgang: No, we don’t change the gear ratio, we use the possibilities offered by the planetary gear set (see http://en.wikipedia.org/wiki/Planetary_gearing). In the Ampera, the transmission runs in dual-shaft operation under 100 km/h – that’s why Clutch C1 is closed. The gear ratio is constant, the rpm variance comes solely from the main motor. At higher speeds C1 opens, at which point the planetary gear set moves to three-shaft operation. The Ampera design is a summation gear – both incoming speeds are merged into one output speed. De facto we thus reduce the main motor’s rpm and feed the rpm necessary for driving speed variance from the generator via the second drive shaft to the transmission.

Stephan: More than once I have taken up the cudgels with irrepressible euphoria for the Ampera and still find the concept brilliant. Sadly, I must admit that I simply need a larger luggage compartment and a rear bench seat. But I’m absolutely sure that this car is going to cause technological avalanches and is 150% suitable for most people!