Recuperated Energy - what exactly does it mean?

[psquare]

Ok, I'm loving all the stats and consumption details in the car, but what exactly does "recuperated energy" mean?

For example, when I look at the stats after my last trrip, it tells me that:

Last trip 6.2 mls
Consumption: 4.3 mls/kWh
Electric distance driven: 6.2 mls
Recuperation: 62.1 mls/kWh
Electric distance driven (since last charged): 51.0 mls

my average recuperated energy is 18.7 mls/kWh, vs 16.5 mls/kWh for the community.

In plain english, what does 62.1 mls/kWh tell me?

 

[BrianStanier]

It's the opposite of consumption. Your average of 18.7 means you travelled 18.7 miles for each kWh of energy recovered by regeneration. You are getting slightly less regeneration than the community average - which probably means you are a gentler driver. Mine is 22.1.

 

[FrancisJeffries]

Recuperation is another name for regeneration. Regeneration - the more commonly accepted term - is the recovery of Kinetic Energy from the car's motion and converting it back to electrical energy which is put back into the battery. That's the "recuperation". It's not a very efficient process, which is why you don't get as much back as you took out of the battery because of the losses due to air resistance, etc., etc., while you're moving.

Note that kinetic energy is 1/2(m*V^2) ("half MVsquared"). So you get four times as much regeneration going from 60mph to stop as you do from 30mph to stop. Or, putting it another way, you recover three times as much from 60mph to 30mph as from 30mph to stop.

So after all that, 62.1 mls/kWh means they're taking 62.1 miles to recover each kilowatt-hour. The smaller value you can get for "recuperation", the better you're doing, but I suggest you don't worry about your average of 18.7miles/kWh. It's not going to affect your range much! So it's a good idea to keep off the brake pedal altogether until your speed is very low.

Oh, and I'm impressed by your 4.3miles/kWh! I get only 3.5, probably because I just can't resist using the car's performance to the full :lol:

 

[psquare]

Thanks for those answers, Brian and Francis ! Very helpful.

I usually drive with the consumption history on the left hand side of the split screen, which is helpful. As an aside: has anybody found a way to move consumption history to the right hand side of the large screen? It doesn't seem to be part of the eDrive options.

 

[PluviaPlumbum]

I would have to disagree with your conclusion there Francis !

I was initially also somewhat confused as to what the numbers were telling me but I concluded that logically the HIGHER the Miles per KWH number indicates that you are driving in a more efficient, anticipatory style of driving by not slowing as much via Regen ( which while better than use of the brake pedal) is less efficient than the use of coasting.

If Psquare is getting 60 plus the he must be very light footed! my own average is only around 24 :roll:

 

[RJSATLBA]

I would have to disagree with your conclusion there Francis !

I was initially also somewhat confused as to what the numbers were telling me but I concluded that logically the HIGHER the Miles per KWH number indicates that you are driving in a more efficient, anticipatory style of driving by not slowing as much via Regen ( which while better than use of the brake pedal) is less efficient than the use of coasting. :roll:

+1 or you are doing a lot of motorway/freeway driving with little speed variation; also, when you do need to slow it is easier to do so solely by coasting than it is at slower speeds because of help from higher wind resistance.

 

[BrianStanier]

I agree that higher numbers are better - unless you are braking so hard that you're mostly using the friction brakes to slow down. But the OP has good overall consumption so I don't think that applies to him. In general coasting is best, regeneration next best and friction braking worst.

 

[psquare]

On this particular trip I was going around 45-55 mph, rural roads and coasting as much as possible.

On a recent long trip on the motorway (most 65 mph on Cruise Control) I noticed that my regen values in the Consumption History screen was almost full bars at the bottom. This seems to support Brian’s explanation.

 

[jadnashuanh]

Look at it this way...constant speed and coasting are the most efficient means of use on any car regardless of its type. Regen is a way to recover SOME of the wasted energy because you have to slow or stop...but, the key here is that it is wasted energy - you can never recover as much energy in regen as you used to get up to speed in the first place unless maybe you were coasting down a very long hill requiring some regen to maintain speed and gravity is doing it verses friction and wind resistance.

But, if you are in nasty stop and go traffic, you'd want to recover as much of that energy as possible verses having to use the brakes...so, it really depends on your driving situation which is 'good'.

 

[psquare]

So if a higher amount for Recuperated Energy in mls/kWh is better, what does it express then?

Does a value of say 18.3 mls/kWh mean that you would recoup 1 kWh if you drove like this for 18.3 miles?

 

[jadnashuanh]

So if a higher amount for Recuperated Energy in mls/kWh is better, what does it express then?

Does a value of say 18.3 mls/kWh mean that you would recoup 1 kWh if you drove like this for 18.3 miles?

Ideally, you'd have NO energy recuperation since you'd be maintaining a constant speed, and there would be no opportunity to recuperate any (via regeneration)!

So, while cruising down the highway, ideally, you'd go LOTS of miles before you showed any regeneration because you're either coasting or just cruising under power. Any time that you slow down, you're wasting kinetic energy, and the car tries to recoup or save via regenerating that energy back into energy it can store into the battery. That conversion operation is never perfect, otherwise, you'd have a perpetual motion machine.

One has to look at both the miles/Kw used and the regen accumulated to evaluate how efficiently you are actually driving. Ideally, lots of miles/kw used, and lots of miles to regenerate any (since that represents only a small portion of the energy used to move you that distance). That's impossible in stop and go traffic, so there, you could easily recoup more energy in fewer miles, but since you may only save 50% of the energy it took to get you moving when you stop (don't take that number to heart...it's just being used for demonstration purposes), every time you slow down, you are throwing away a portion of the available kinetic energy. The ideal would be to never throw any energy away that could be recouped in the first place! You must stop sometime, so you will generate some. Any time you use the brakes verses letting the car slow you down, you're wasting energy as well.

IOW, regen is a method to recoup some of the energy used to make the car move when you then need to slow down...ideally, you maintain a steady pace, and there's almost none that can be recouped.

 

[cove3]

>>>you may only save 50% of the energy it took to get you moving when you stop (don't take that number to heart>>>>

Shouldn't there be a graph showing what that % is at various speeds (which thus equals momentum/kinetic energy) If it's mostly 90% it's not worth coasting but if it's mostly 40% it would

 

[jadnashuanh]

Personally, I don't worry about it. Avoid using the brakes at all unless absolutely necessary, and try to be steady and coast to maintain speed, and you're going to be fairly efficient. Your route and driving techniques will determine the opportunities for regen, but the only thing there is regen is better than braking, and coasting is better than that.

 

[psquare]

regen is better than braking, and coasting is better than that.

Thanks Jim for taking the time to explain this. Very helpful and I am glad I asked the question in this thread.

So far, I always thought that having the car on the left side of the "pendulum" (as I call the light moving between 'Charging' and 'ePower') is better than central (coasting).

I wrongly believed that coasting merely means a "+/- 0" situation where the consumed energy equals the recouped energy and "Charging" (left of coasting) means that more energy is going back into the batteries than being consumed.

Thanks again!

 

[PluviaPlumbum]

Just for balance here; lets not put the pursuit of ideal consumption figures which for some of us is a worthy goal, ahead of driving responsibly when in traffic and inconveniencing other road users. The temptation to be fixated on the various graphs and numbers presented while driving can be dangerous on our crowed UK roads!

My own problem is being tempted by the whip crack acceleration when I'm in the mood for fun!

 

[psquare]

Just for balance here; lets not put the pursuit of ideal consumption figures which for some of us is a worthy goal, ahead of driving responsibly when in traffic and inconveniencing other road users. The temptation to be fixated on the various graphs and numbers presented while driving can be dangerous on our crowed UK roads!

My own problem is being tempted by the whip crack acceleration when I'm in the mood for fun!

(I think) I know what you mean, but to me the i3 is a car that was designed with energy efficiency and overall environmental impact in mind.

I very rarely drive the car in Comfort, because I consider the acceleration over the top in most cases. However, it is nice to know that I have some ooph when I need it.

 

[jadnashuanh]

The gain on the accelerator is higher when in comfort mode, but a light foot there can achieve the same power consumption as in any of the eco modes (well, if you turn off the climate control, you can match eco pro+). But, it takes finesse...the car does some of it for you in eco pro and + modes.