Stoaty's Guide to Energy Efficient Driving of the Leaf

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TonyWilliams said:
I used the hyper accurate technique of driving 15mph, then 10mph, noting no significant difference, and proclaiming the middle, 12.5mph.

Oh, I see! I understand now. Thanks for making that clearer. :D
 
Stoaty said:
abasile said:
But I'm not convinced that impeding the flow of traffic is worthwhile just for the sake of saving some kWh.
I agree 100% and never impede the flow of traffic. However, here is my definition of impeding the flow of traffic, and what is not impeding the flow of traffic (although others may not like it) ...
Thank you for the explanation. Actually, when I need to stretch the range of the LEAF, I drive in what seems to be a very similar manner. And I generally feel no obligation to exceed the posted speed limit unless I am in the HOV lane, which I haven't yet used in the LEAF. Over the years, I've annoyed more than a few drivers by sticking to the speed limit. So you can't please everybody. It is pretty cool that you're able to maintain such high efficiency. But it can also be cool to smoke ICE cars at times. :mrgreen:
 
abasile said:
But I'm not convinced that impeding the flow of traffic is worthwhile just for the sake of saving some kWh. I'm not just saying this because of "haters" out there. At this point, we are the ambassadors for a new way of driving, using electricity. Some of us, like my family with our Christian-themed license plate frames, use our cars to promote other causes as well.

You could impede traffic and use reverse psychology, put on some atheist bumper stickers or perhaps pro Obama propaganda.. save the Planet and America at the same time!
 
TomT said:
My goal is to be at the absolute bottom of the list in Carwings, drive as hard and as fast as I can, use maximum A/C, and always arrive home with as low a battery as possible! :lol:

I agree, the car is for DRIVING, not tree hugging.

OK Let's compare

For August I'm ranked 2,604

How low can you go? :ugeek:
 
After a careful, scientific, and very detailed experiment, I found that I use the least battery power when the car is Off. I now plan to only use the car downhill and in that mode, and then have it towed back up. Extensive number crunching shows that I may be able to achieve 100 M/KwH using this new and exciting mode of driving! :lol:

TonyWilliams said:
I used the hyper accurate technique of driving 15mph, then 10mph, noting no significant difference, and proclaiming the middle, 12.5mph.
 
Meh, driving this slow just makes annoying "big-car" owners hate EV's and trash talk them. I drive in traffic, and I pull 80 KW at stop lights to show "Mr. Big Car Tiny Weanie" that EV's can get up and go.

And for August, our Leaf was ranked 1,003. :)

If I -really- need more range, I just drive smarter on surface streets instead of pulling 75 on the highway.
 
TomT said:
After a careful, scientific, and very detailed experiment, I found that I use the least battery power when the car is Off. I now plan to only use the car downhill and in that mode, and then have it towed back up. Extensive number crunching shows that I may be able to achieve 100 M/KwH using this new and exciting mode of driving! :lol:
I may have to add that to my list at #14. Thanks for contributing an advanced technique! ;)
 
i am not worried about being a missionary for EVs when I drive, though it occurs to me on occasion when I stick to the speed limit.

I drive a very similar gas-saving way in my stick shift ICE. Lots of coasting and hot driving only when necessary or I need a different kind of amusement.
Mostly, I am concerned about not wasting energy, whatever the source. Accordingly, I steam quietly inside when I ride with the kids or my wife at the wheel. they like to get to the stop lights fast and wait, and use the brakes.

I dont do bumper stickers, and am always curious about those who do, especially folks who want to advise me about their religious preferences and perfections.
I was always taught to respect the freedom of religion, which includes, to me, the freedom from religion. I understand some faith-based folks (not limited to xtians) are required and revel in trying to convert me and everyone else.
 
JPWhite said:
I agree, the car is for DRIVING, not tree hugging.


When I first started driving the car, I did the same. But since my typical day stretches the range limit of the car, it's easier to conserve than wait around in the middle of the day for a charge.
 
Stoaty said:
I am pretty sure I saw that 30% number on MNL. When I looked up Prius regen efficiency, best guesses were 30-50%. If it is better than that, I would like to see a reference. Don't know the real answer, but doubt the 80%. That would be phenomenal.
There are several different numbers that people use. 30% would be at the high end for the overall efficiency increase but too low just for the efficiency of turning kinetic energy into chemical energy. Of course it can't be greater than 90%. A guess of 70% at the highest end wouldn't be bad (80% drivetrain efficiency X 90% charging efficiency).

This is one way efficiency. Roundtrip efficiency would be more like 55% assuming your drivetrain was 80% efficient (80% out X 70% back).

The Prius battery is considerably smaller which will limit the amount of regen it can handle.
 
SanDust, can you explain that "80% drivetrain" number. Are you literally talking about losses in the reduction gears and differential? I have no expertise in this area, but I would have guessed less than 5% loss there, since there is no transmission as such. Any losses would have to show up as heat. Does the transaxle really radiate that much heat? It doesn't have active cooling, does it?

Ray
 
planet4ever said:
Does the transaxle really radiate that much heat? It doesn't have active cooling, does it?
Ray

The three gear set reduction from the motor to the final drive uses one liter of lubricant. There is no effort to provide any cooling whatsoever (no fins cast in the housing, no external coolers, no radiator coolant pumped in, etc).

The motor itself (liquid cooled) would act as a heat sink, however.
 
planet4ever said:
SanDust, can you explain that "80% drivetrain" number. Are you literally talking about losses in the reduction gears and differential?
All the losses going from the battery to the wheels. That would include the reduction gear and the other mechanical linkages as well as the chemical-magnetic-electrical-mechanical conversion losses. I don't know about the Leaf specifically but 80% is usually assumed to be the efficiency over a range of speeds for an EV. Obviously at low or high speeds you'd have more losses.
 
SanDust said:
The Prius battery is considerably smaller which will limit the amount of regen it can handle.
Does this mean that the Prius uses the friction brake more often than the Leaf?

Also, I can understand the Prius battery can't handle the last amount of regen from going down hill for a long time, but I have to believe that the Prius battery is designed to be large enough to recapture most of the energy from a typical stop from 45 miles to 0, no? Otherwise, it seems very inefficient not to be able to recapture all the kinetic energy just because the battery is not large enough to store it.

But then again, if the switching point from battery to ICE is 15 miles, is that safe to assume that because the battery is only big enough to propel the Prius to 15 miles, then it's only big enough to capture the kinetic energy from 15 miles to 0?
 
Volusiano said:
but I have to believe that the Prius battery is designed to be large enough to recapture most of the energy from a typical stop from 45 miles to 0, no?

You're probably right, but regen comes in two flavors. Braking and coasting.

The regen brakes slow the vehicle down, the drive motor regens the gradual speed loss when coasting. It's my understanding that regen while coasting gets more total energy back than braking does.

I have been simply amazed at the LEAF being able to capture back as much as 25% of energy through regeneration even the way I drive :) Of course Carwings tells me that, not sure how much we can rely on those statistics, but hopefully its in the ball park.

JP
 
For Regen, assuming above average values, the efficiency for some of these steps might be 97% or 98%, and others only 93% or 92% ... so, without real values, let's just assume each is 95% for now:

1. mechanical road to motor
2. motor to electrical
3. AC to DC in the Inverter
4. energy loss into battery
5. energy loss leaving battery
6. inverter converts DC to AC
7. motor drive losses
8. mechanical to road losses

The net efficiency is the product of all of the efficiencies:
0.95 x 0.95 x 0.95 ... (8 terms) =
0.95 ^ 8 = about 66% (a VERY good figure)

In practice, one usually gets lower overall Regen efficiency.
 
Volusiano said:
SanDust said:
The Prius battery is considerably smaller which will limit the amount of regen it can handle.
Does this mean that the Prius uses the friction brake more often than the Leaf?
Yes, unless one learns to brake gently and gradually, the Prius will generally end up using the friction brakes more than the LEAF. With the Prius, regen maxes out at about 20 kW, compared to 30 kW with the LEAF.

Volusiano said:
Also, I can understand the Prius battery can't handle the last amount of regen from going down hill for a long time
That is correct. However, the Prius does have one sort of advantage over the LEAF on long descents. The ICE (internal combustion engine) can provide compression braking, thereby eliminating or reducing the need for friction braking when going down mountains. With no ICE, the LEAF is forced to rely on friction braking if the battery is too full. So, in the LEAF, one should avoid higher states of charge prior to big descents; then you come out way ahead of the Prius in terms of being able to recapture energy.

Volusiano said:
I have to believe that the Prius battery is designed to be large enough to recapture most of the energy from a typical stop from 45 miles to 0, no?
Yes, the Prius battery is more than large enough for that. But you need to brake gently and gradually to recapture that energy.

Volusiano said:
But then again, if the switching point from battery to ICE is 15 miles...
If one accelerates very gently, it is possible to go as fast as 45 mph in the third-generation Prius (2010/2011) without using the ICE. The only problem is, if you drain the battery too far, the Prius will be forced to run the ICE as a generator to recharge the battery, which will reduce overall efficiency.
 
Stoaty said:
For those like me who want to conserve as much energy as possible I offer my recipe [...]
6) Look ahead at the speed of traffic and the next 1-2 stoplights. Note whether the lights are "stale" (have been green for a while and likely to change soon) [...]
I use a couple of hints for this:

1. Pedestrian crossing light: if it's white, it means that the my light will be green for a while and there is no need to speed up to make the light and avoid having to stop. If it's blinking red, I may need to hurry up if I want to avoid stopping. (Around here, the pedestrian crossing light changes to solid red at the same time as my light changing from green to yellow.)

2. On a familiar stretch of road at a familiar time of day (e.g. commute), the number of cars at an upcoming red light tells me whether it's about to turn green any time soon. Relatively few cars means that the light has just turned red; relatively many cars means that the light has been red for a while and can be turning green soon.
 
LEAFfan said:
7. To stay in the neutral bubble and to keep your speed constant once up to speed, you can use the CC by going one mph over what you want, then push down quickly on the button and it will put you in the neutral bubble.
You post this a lot, and I have tried this several times but it never works. The car soon slows down 1 mph and starts using power at much the same rate as before.
 
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