Driving Cycle

[George S. Bower]

Here is a my driving cycle: 37 miles up with an elevation change of 2500'. The return home is the same, only down 2500' elevation.

A little program I wrote predicts AER of 23 miles on the way up. There is no charging station so the rest of the trip is in CS mode. ie 14 miles remaing on the trip up and 37 miles on the way back.

Here is the engineering question: Assuming the volt had the option of selecting which part of the trip I use the ICE, how would I get the least number of gallons burned on the round trip.

Run ICE up the hill?, or drain the battery in the first 23 or so miles and complete the trip on ICE power.

I have formulated an opinion but don't want to taint your input.

What part of the trip would be best to run in all electric?? and what part of the trip would it be best to run the ICE?? (I don't think this is an option in the Volt so just pretend.)

[pdt]

I doubt it makes much difference, but however you do it, you'd want to maximize regenerative braking on the way down.

[Rooster]

Use electric (the 8 KWh) for the uphill travel...it is a more efficient mode of conveyance. Use the charge sustaining mode for the downhill run. Since downhill will be assisted by gravity, the resultant MPG should be quite high. Plus you will likely capture a significant amount of regenerative braking energy to assist with any needed acceleration once you’re down the hill. I'd think the ICE would pretty much be idling on the downhill leg of the trip.

Merry Christmas!

[misslexi]

Go to work all electric, or as much as possible. Plug in at work. Return home all electric. Plug in, repeat.

[Koz]

If you could control the genset manually, the most efficient implementation would most likely be:
-Run genset from the start at it's most efficient output (max kwh/gal) if this output is less than uphill average power draw. If it isn't, start genset once battery is depleted to the point where a single genset run during the uphill run will leave a battery SOC that will allow the remainder of the trip to be completed without restarting the genset. Either way, turn off the genset when battery SOC is just sufficient to return home with a depleted battery but w/o restarting the genset.

The genset will be run most efficiently this way, including minimizing startups. Also, traveling downhill with genset running may waste regen opportunities if max regen power plus generator power higher than max recharge power. Either way, recharge rates above the ideal are less efficient and get worse as the rate gets higher.

The problem is that it is impossible to accurately predict what your future real world energy needs will be, thus it's difficult to time the genset shutdown accurately.

[George S. Bower]

My thought was: to minimize fuel consumption, maximize the amount of miles driven in electric mode. So, run the generator on the leg up just long enough so that you get all the way home on electric. and ideally with near zero usable electric in the battery ie ICE just about to come back on. You would also get the advantage that you would be running the ICE on the way up at a high load condition which results in a lower SFC.

So I guess I agree with Koz.

I wonder what Tom would say??