[Mr.Woolery]

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.

 

[bjrosen]

Gentle acceleration, hold the speed steady, keep the speed down (K=1/2MV^2 i.e. energy is the square of the velocity), coast to slow down, use regen paddle if coasting isn't sufficient, use the brake only for the final stop.

 

[hellsop]

Take everyone's opinion with a box of salt, except Ari's. He's the authority on this until someone beats his range record.

 

[srmarti]

IMHO the OP is putting too much effort into trying to out-think the car. Just avoid abrupt accelerations (in both directions) and drive at a reasonable speed.

 

[srmarti]

Take everyone's opinion with a box of salt, except Ari's. He's the authority on this until someone beats his range record.

Even ari's methods aren't going to fly for normal use with passengers that want to actually get somewhere. His record was set going around in circles at 25mph. If you want to play around, that's find as long as you don't annoy or endanger others.

 

[Qinsp]

Gentle acceleration does a couple of things. First, it reduces your average speed which reduces the aero losses for the trip. Second, electrical losses climb with amperage. High amps lose more power than low amps.

I sort of wish the Volt had a knob you could adjust for peak kW used. When you floor it or turn the knob, full power is instantly available, but otherwise, it caps your power use. This is more important when the terrain you drive in is not flat. It is the reason a trained foot will beat a cruise control in the hills. A cruise control often accelerates more than what is really necessary.

But to be honest, I extend my range for fun, the amount of money it saves me is sort of pointless.

 

[Mr.Woolery]

Yeah, I get the gentle acceleration part, and follow that as a rule (I consider 20kW to be my target max throttle input for acceleration from a start). I'm also pretty good at coasting along and timing things (traffic/lights/etc) so that I minimize brake usage.

At this point I'm just playing around with a couple techniques for maintaining cruise speed. Maybe I am overthinking it....LOL
It's mainly an exercise in trying to maximize the EV range for the car, because nerd reasons.

I also with that the Volt had an adjustment setting for Peak Throttle kW.

 

[rmay635703]

Due to the way the volt handles its 2 motors light acceleration is almost always best (under 20kw) or you fall out of the more efficient 2 motor mode.

Also it's best to let off the brake and let the car "launch" at idle then slowly get into the throttle.

P$G does not work on the volt in ev mode, gas mode is questionable as well.

Once you are up to your goal speed set a kw/mile goal and hold there, your tire inflation and local temperature affect what you can expect. Battery heater and climate controls dramatically affect the efficiency at low speeds which changes tactics.

I usually shoot for 6miles per kw and let speed go up and down holding it there as much as possible.

Long steep hills are best accelerated up to a bit faster than normal, bleed speed up to the lower mph limit, then neutral coast as long as safe off the other downhill side.

I have achieved 68-72 miles ev range all summer using the above techniques on a 2013
Slow and steady wins

 

[Dutch]

My experience has been slow accel and decel and moderate (less than 60mph) for maximum efficiency.
Barring that, riding the wake of a tractor trailer (not "drafting" right behind, just in the airflow) helps quite a bit.

But honestly, I played around for about 6 mos to see what could be done, and then just went back to driving since the Volt is so much more efficient than my Jeep that anything I did was an improvement.

 

[eDreamin']

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.

Well, my middle-school math skills would indicate no benefit of 20kW for 3 seconds (that would be 60kWs [kilowatt-seconds, right?) over 10kW for 6 seconds (also 60kWs). Having said that, I must echo some of the other responders here:
1- Have fun trying to squeeze out every possible mile
2- Don't do anything dangerous (obstruct traffic, stare at the dashboard display too long, etc.)
3- When you tire of the games, just drive it like any normal car, and you'll find out all the extra effort was a waste of your time.

But stop every now and then to try to remember when you last filled the tank with gas. I have set my display so that I just see the basic data (no leafy green ball, no plus-or-minus kW readings to constantly "monitor"). I think I'm a safer driver for it. I think we all would be.

 

[bjrosen]

My habits changed when I got the Volt, I drive it to maximize EV range. It has nothing to do with costs because in my case electricity is more expensive than gas but in either case vastly more economical than by old car which had a Hemi. I just prefer the electric motors over the engine, I don't like the noise the engine makes. If the Volt had a 100 mile electric range I wouldn't obsess over it but the 53 mile range (which I can frequently stretch to 60) is on the hairy edge for many of my local trips. One of my frequent trips is 29 miles each way if I take a back road but is 37 if I take a highway. If everything goes right I can do the round trip on battery but on several occasions I've missed it by a block which is pretty frustrating. Other trips such as into Boston are about 50 miles, if I do things right I can get to a garage with an EVSE with a few miles to spare, unfortunately on the return trip I generally miss by a mile (I'm guessing it's an uphill vs downhill thing).

 

[jupitermoon]

Live your life man...even at its worse you are driving a car that is far more efficient than every other ICE out there.

Lot's more important things to worry about. Just my opinion.

 

[ampera_jed]

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.

 

[wws]

Use "D" and drive like you are in snow - maintaining your momentum as much as possible without excessive stop and go. If traffic is light, use cruise control. (It works down to 25 mph.) If you have any downhill portions, maybe shift to "N" and coast to gain some free speed.

 

[canehdian]

Moderate acceleration.
Bursts of high power acceleration, per physics, wastes more energy in the wires with higher current.
The motor will have an efficiency curve that's an arc - the efficiency sweet spot is somewhere between minimum and max power.
The inverter will also have a similar efficiency curve.

In real world these items probably only account to a couple % difference and not noticeable when thrown in the mix with all other variables.
How you drive (i.e. coasting vs repeated stop and starts) has far greater bearing on overall efficiency than actual efficiency of the electrical components at max load vs med load vs min load. The electrical components may go from 90 to 95% efficiency.
But what good is that if you have to regen at 80%?

 

[llninja]

Even ari's methods aren't going to fly for normal use with passengers that want to actually get somewhere. His record was set going around in circles at 25mph. If you want to play around, that's find as long as you don't annoy or endanger others.

Ari still used pump and glide, shifting to N, and it wasn't exactly in circles, more like rectangle at FedEx field (washington redskins). I've given up hypermiling. I now just drive and don't worry about braking any land hypermiling records.

 

[srmarti]

Ari still used pump and glide, shifting to N, and it wasn't exactly in circles, more like rectangle at FedEx field (washington redskins). I've given up hypermiling. I now just drive and don't worry about braking any land hypermiling records.

OK I got the geometry wrong.

The fact is still that all he did was go around and around instead of going anywhere. It's basically just a stunt. I once managed to go 50 miles on a charge chauffeuring three passengers to real destinations with the HVAC set at 74 vs ari driving around FedEx field at 25 mph, with very overinflated tires, HVAC off, and shifting in and out of drive to go about 80 miles. My passengers would have been very upset if I drove like ari.

 

[llninja]

OK I got the geometry wrong.

The fact is still that all he did was go around and around instead of going anywhere. It's basically just a stunt. I once managed to go 50 miles on a charge chauffeuring three passengers to real destinations with the HVAC set at 74 vs ari driving around FedEx field at 25 mph, with very overinflated tires, HVAC off, and shifting in and out of drive to go about 80 miles. My passengers would have been very upset if I drove like ari.

Somebody's got to do it in the interest of science. I can't imagine driving the same route around for 4 hours, although maybe if I were going 200 MPH in a Sprint Cup car around Daytona, that might be fun.

 

[VoltenRock]

I appreciate the original question because I have the worst possible commute for the Volt--all highway, with constant UP/DOWN little hills. Round trip is 56 miles with no charging at work, so I I get daily feedback on whether the methods were effective per charge.

On this terrain, I can get acceptable EV range by trying to keep a steady 19 kWh from the motor. This means I slow down (sometimes substantially) uphill and then recover the speed a bit downhill again. Of course, this is terrible for anyone that has the unfortunate luck of being behind me (in that case, I usually just forget trying to maximize it and maintain speed).

Whether 19 kWh is the "sweet spot" I don't know--but by aiming for that target, I've been able to at least minimize the loss on the highway.

 

[srmarti]

To me that's the sort of "hyper miling" stuff that annoys and endangers others. Around here even driving the posted limit P.O.s some drivers. I just more or less drive "relaxed" remembering I'm on a public road and not a race course.