In your experience, is it more efficient to give short bursts of relatively higher throttle/kW output levels with coasting in between, or to "hold" the throttle longer at lower thottle/kW levels to maintain a certain speed?
I've been experimenting with trying to maximize my efficiency & range during my commute. It's ~18 miles one way, all surface streets and fairly level (few small ~5ft hills here and there), with speeds seldom exceeding 45mph. Pretty ideal conditions for the Volt and for experimentation with efficient driving. Under normal acceleration from a stop up to cruising speed, I'm generally keeping the throttle input at ~20kW or less.
One method I've used for maintaining cruising speed (let's say, of 35-40mph) has been to maintain a steady throttle input somewhere between 8-15kW, depending on conditions. Another method has been to use short 3-4 second bursts of 18-20kW throttle inputs to nudge the car back up to cruising speed after coasting (anywhere from 5-15 seconds, depending on conditions) and losing 2-4mph of speed. Under both experimental conditions, I'm maximizing use of coasting wherever possible.
I'm still on the fence as to which is more efficient, though I'm leaning towards the "burst" throttle method as being more efficient since I'm guessing that 20kW @ 3sec is less than, say 10kw for 6+ seconds. The main drawback of the burst method being that the ride is less smooth due to the oscillation of acceleration & coasting compared to the "constant" throttle method.
Any thoughts on your experiences?
Side note regarding efficiency: My Volt is still "learning" what the estimated range per charge would be as I've only had the car for a month now. For example this morning, it was estimating range of 51 miles after a full charge. I used 3.3kWh for my 17.7 mile commute (pretty average, my best so far has been 3.0kWh for the same trip), and the range estimator says I still have 38 miles left.
You're asking a good question which I have also been looking at and trying to get the tinyith last energy out of.
As an engineer I would have ordinarily said that it is best to maintain a constant power level, so not tiny amounts then surges, but just a steady delivery.
That's what the theory might say, but I don't quite believe it because it doesn't always seem to work that way.
If you look at the efficiency map for the single motor, and then at the dual motor, then in either case you can see the higher efficiencies are nestled in the middle of the torque map, so in actual fact to get energy down on the road in the most efficient way, the motor side of things suggests that you might be better off aiming for mid-torque levels rather than 'as little as possible' where it is less efficient.
However, if you were to aim for mid torque levels then that would typically be into the upper 30 to 50 kW range, and then you are drawing 100Amps, and the battery is not operating at its most efficient.
So there must be some point away from those mid torque levels where the motors are still pretty efficient, whilst the battery has moved towards its most efficient point, and you need to find out where the best point is. I think it is probably around the 16 to 30kW range, so with this set of thoughts, you probably want to avoid less than 16kW (unless you are using almost nothing), and stick to 16 to 30ish.
So, yeah, I think a bit of squirt and glide works here for the motors, and I think it also works for the batteries because as the plates become discharged of the immediate charge on them, then they can repolarise (that is to say, they recover their voltage after a period of discharge) during the moments you come off the power.
