Hi Michel
> Ed's sensible objection is that IF your battery is empty -- which BTW is most probably the case otherwise you wouldn't be running on the genset. Whoa - Michel, that is the totally wrong assumption. The genset cuts-in much sooner; the battery cannot be allowed to ever go empty as this is harmful ! But unlike the Prius (where the motor kicks in for every hill) the Volt genset only kicks in when the battery array gets to a certain level - say 50% depletion. I do not know the actual number but it is much higher than you are thinking. IOW Long before the batteries are completely empty, the genset comes on and stays on at **full speed** until they are brought back up to a preset value of charge by an onboard computer. The arrangement is designed so that the *average requirement* of power is met by the genset (or more), instead of the peak requirement. Of course, there could be a situation where the driver wants to draw more than the average for a very long time-- say to go 100 mph, well over the speed limit in most places - and in that case, the Volt (or an optimized volt-clone) is not a good choice. You cannot please everyone. In a normal ICE you may need 100 kW of peak power to go from say 0-60 in ten seconds. With the Volt you can do this repeatedly, since you electric motor is sufficient, even though your genset is too small by half. And the genset will kick in and recharge long before the batteries are drained. OK - Can we go from there to needing significantly less than half of the peak power requirement? That is an interesting question because the hypothesis that you can do it technically might not give the driver the "feel" that he needs for a surge of on demand power. IOW the issue would be this. If the average power required for all driving is 35 kW over an extended period - for a light car of say 3000 pounds; (and that figure has been published) - yet - the peak required for hills and passing is 100 kW - then can you get by with the very minimum in your genset, or do you need to "pad that" up to 53 kW, as the Volt is doing? > Isn't he right to conclude that the genset must be able to provide the full power, as it does on the GM Volt? No, not "full power" if by that you mean "peak" .... or should I say: Yes and no. He is correct to conclude that the genset must be able to provide the average power but not the peak power. However, from there-on your (not Ed's) second assumption that the GM Volt needs 53 kW for "full power" is incorrect. It needs far more than that for peak power, and less than that number for average power. Get it? AFAIK from published figures, a car in this weight range and air resistance etc. needs much less than 53 kW for average power and close to 35 Kw, which is the number chosen because this has appeared in print -- but please -- feel free to correct that number, if you can find an actual test or evidence which proves it to be wrong. Jones
