In the Wednesday, Oct 13,'10 WSJ an article with this title appeared on page B3. Without belaboring the point, GM, has been less than forthcoming about one detail of the VOLT drive system. Up until now it has been presented as a SERIES mode hybrid----in fact it It is not; it is a Parallel mode machine meaning at points the drive can be a combination of electric AND mechanical from the ICE.
The VOLT in recent versions has been presented as having a final drive that powered by a mot/gen to provide power OR braking. The ICE has always been presented as driving another mot/gen whose function is to recharge the battery after about 40-50 miles AND to provide the power to drive the other mot/gen. Typical drive would entail electric for the first 40 miles, then the ICE starts and can drive the some additional 300-400 miles consuming about 10 gallons of gasoline.
To this writer it has always been curious that GM descriptive material was vague about the precise relative position of the mot/gens and the ICE. NOW it is claimed this vagueness was intentional UNTIL the patent had been secured. (a little smoke and mirrors probably). What was concealed was a planetary gear set that was positioned to operate essentially as an electrically operated clutch, when actuated that coupled the ICE crankshaft directly to the mot/gen shaft that drives to the differential and the front wheels. When the one shaft to the planetary gear set was free to rotate the ICE was disconnected
to the ground drive—when it was stopped, the ICE was able to deliver power to the differential, hence to the front wheels.
Sounds damned complicated----is there an advantage?
LET'S TALK EFFICIENCIES:
1) Putting a charge into or removing a charge from a good NiMh OR Li-ion is about 90% each way.
2) Good mot/gen are bout 90-93% both as a motor and as a generator i.e. mechanical to electrical.
Hence in a braking cycle the combined efficiencies are (0.9x0.9x0.92x0.92) = 0.69=69%
For the Series Mode VOLT in the cruise cycle where the battery is neither charged or discharged the efficiency is (0.9x0.9)= 0.81 or 81%
It is this 19% that the direct drive from the ICE above 60 mph that is mostly recovered. Is it good---------I think so? Even though the pricing is way off the mark. BTW make no mistake GM has the PRIUS clearly in it sights, particularly the rechargeable PRIUS about to be announced.
The race for the "family car" replacement just now looks like PRIUS, GM VOLT and HYUNDAI SONOTA HYBRID.
All three of these vehicles designs will recover at east 70% of the energy otherwise lost to brake pad heat. All can be operated as "Plug-In Electrics).
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