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Good question. The duty cycle would definitely depend on the accumulator size as well as the engines size. My brothers Prius cycles the engine of and on frequently and before actually seeing that I had concerns about cycling frequency.
Back to a direct answer. The cycling would be a function of the average of energy demands. In the INNAS link in my earlier posts they stated an 11% average of engine on cycling. Much lower at low average speeds and higher at greater average speeds. My best guess would be about every .6 miles at 55 MPH and on for probably 20 seconds while powering the vehicle and charging the accumulator. That would make it close to 50% on and 50% off at 60 MPH.
That does not factor in the aero efficiency of the body which would reduce the cycling percentage. I have to guess again at probably 50-50 at 70 MPH. This would also depend on the size of the engine which would reduce the 50-50 to 40-60 or more.
It's hard to nail down any absolute figure but the overall 11% of the INNAS configuration through the whole European cycle is probably fairly close, but the percentage would definitely change depending on your average speed. I would guess at 45 MPH average it would be 45 seconds off and 15 seconds on. Probably about the same as the P&G ratio which is 2to3 to 1 ideally. Even the weight of the vehicle would affect the percentage.
regards
Mech
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