Coasting consumes a kilowatt - crazy

[fcleaf]

If you can't then you can age faster worrying over 1Kw and wind drag limits.

Ahh. I was wondering where those grey beard hairs were coming from...

I'm not worried about it at all, of course. I am curious. Coasting in an ICE drops the RPM (ie 5000 to 800) and removes the load on the engine significantly changing fuel use/savings. I am curious what the effect is in the Leaf or a similar EV. It seems that with the meters many of you have attached to show instantaneous power use, and the natural inclination to testing, you represent a ready resource to answer that curiosity. :mrgreen:

As you say, properly using D mode, one can achieve a 0 charge/discharge state, presumably canceling out the parasitic loads without inducing much drag. Not to go too far off-thread, but do you find it more efficient to drive in D vs B for regular flat surface driving? Presumably the more frequent you stop, the better the B mode is, but in long stretches, does the D mode provide for better efficiency?

Thanks again for allowing me to sleep at night

 

[garygid]

Most of the power usage values are derived from the Pack
current, usually filtered. Still, the Pack current, even averaged,
seems to fluctuate a lot, and at rest I have seen the car report
current going into the battery, rather than out.

Apparently the reported current is not very accurate, thus
the derived power flow is not very accurate, especially at
low current / power levels.

 

[TomT]

I believe that it comes from the pack Hall Effect current sensor which we already know to be less than completely accurate...

Apparently the reported current is not very accurate, thus
the derived power flow is not very accurate, especially at
low current / power levels.

 

[EVDRIVER]

If you can't then you can age faster worrying over 1Kw and wind drag limits.

Ahh. I was wondering where those grey beard hairs were coming from...

I'm not worried about it at all, of course. I am curious. Coasting in an ICE drops the RPM (ie 5000 to 800) and removes the load on the engine significantly changing fuel use/savings. I am curious what the effect is in the Leaf or a similar EV. It seems that with the meters many of you have attached to show instantaneous power use, and the natural inclination to testing, you represent a ready resource to answer that curiosity. :mrgreen:

As you say, properly using D mode, one can achieve a 0 charge/discharge state, presumably canceling out the parasitic loads without inducing much drag. Not to go too far off-thread, but do you find it more efficient to drive in D vs B for regular flat surface driving? Presumably the more frequent you stop, the better the B mode is, but in long stretches, does the D mode provide for better efficiency?

Thanks again for allowing me to sleep at night

I don't have "B" and I never use "N". There is no reason other then wearing out the switch. I always drive in ECO because of the terrible regen in "D". The LEAF still has poor regen compared to other EVs and wastes much energy to the brakes in many cases.

 

[Ingineer]

Shifting into "N" removes all drive signals from the IGBT's in the inverter, effectively free-wheeling the motor. It does not "fake" anything! It's no different than when stopped in drive with no pedal action.

The "house" loads in the LEAF are substantial, and of course continue even when you are in "N".

As TomT mentioned, the LEAF measures power in/out of the battery with a hall-effect current meter, and it is subject to drift, offset errors, and is generally inaccurate at low currents, so don't assume because the LBC (Battery Controller) reports more draw than you expect in "N", that the draw is real.

-Phil

 

[mkjayakumar]

EVDRIVER, I disagree on your conclusion that 'D' or 'ECO' is better than driving in 'N'. After driving 70 mile round trip commutes every day in the last few months, I can tell you with certainty with my empirical observation that coasting in Neutral whenever possible is the best way to increase efficiency and range. And also driving in 'D' is far more efficient than 'ECO' as long as you don't do rabbit jack starts and coast to a stop light preferably with 'N' and shifting to 'D' when you have to press the brakes for a full stop.

I perhaps shift between 'N' & 'D' over two dozen times in my everyday commute, and it all looks like too much but after sometime it just becomes 2nd hand nature. Moreover I don't think you are going to wear out anything by shifting that many times.

Leaf really goes quite a bit distance in 'N' on level ground without losing speed that much. I haven't measured it but at 50 mph I think I go can a mile or so before it drops to 45 mph.

 

[EVDRIVER]

EVDRIVER, I disagree on your conclusion that 'D' or 'ECO' is better than driving in 'N'. After driving 70 mile round trip commutes every day in the last few months, I can tell you with certainty with my empirical observation that coasting in Neutral whenever possible is the best way to increase efficiency and range. And also driving in 'D' is far more efficient than 'ECO' as long as you don't do rabbit jack starts and coast to a stop light preferably with 'N' and shifting to 'D' when you have to press the brakes for a full stop.

I perhaps shift between 'N' & 'D' over two dozen times in my everyday commute, and it all looks like too much but after sometime it just becomes 2nd hand nature. Moreover I don't think you are going to wear out anything by shifting that many times.

Leaf really goes quite a bit distance in 'N' on level ground without losing speed that much. I haven't measured it but at 50 mph I think I go can a mile or so before it drops to 45 mph.

Based on your driving skills and flat geography. Regardless of those variables you are assuming a very specific and controlled driving style for your environment that has minimal relative gains and can still be obtained in D or ECO. A skilled driver can drive the LEAF the same way you do without ever using the neutral switch and get the same results because there is always a neutral spot on the pedal. The LEAF regen is so easy to manipulate because it is so weak. Putting that aside if you live in SF your theory is invalid because you need all the regen you can get because of the terrain and it is stil not strong enough. On the other end of the spectrum is also a extreme group of folks that creep to a slow agonizing speed and coast to each light slowing traffic and holding people to idle and waste gas at missed lights, they are some of the most frustrating hypermiler drivers around and I certainly won't ever be part of the old school Prius pulse and glide crowd. If they could push their cars from light to light they would. It is best to use what works for you and what you are comfortable with but constantly toggling the car to neutral will shorten the switch life, that is a mechanical fact. The switch may last 500 years or less than the life of the car but the wear is increased because there are moving parts with friction, not to mention they are made by Nissan. I often "coast" down steep grades and never use "N" where one could actually loose efficiency to exponential wind drag instead of using regen at a slower constant speed. I read a Nissan TSB that said they log the number of neutral cycles ont the LEAF computer and if they are over 12 a day at speeds over 10 MPH it voids the warranty on the shifter

 

[LEAFfan]

EVDRIVER, I disagree on your conclusion that 'D' or 'ECO' is better than driving in 'N'. After driving 70 mile round trip commutes every day in the last few months, I can tell you with certainty with my empirical observation that coasting in Neutral whenever possible is the best way to increase efficiency and range. And also driving in 'D' is far more efficient than 'ECO' as long as you don't do rabbit jack starts and coast to a stop light preferably with 'N' and shifting to 'D' when you have to press the brakes for a full stop.

I perhaps shift between 'N' & 'D' over two dozen times in my everyday commute, and it all looks like too much but after sometime it just becomes 2nd hand nature. Moreover I don't think you are going to wear out anything by shifting that many times.

Leaf really goes quite a bit distance in 'N' on level ground without losing speed that much. I haven't measured it but at 50 mph I think I go can a mile or so before it drops to 45 mph.

Based on your driving skills and flat geography. Regardless of those variables you are assuming a very specific and controlled driving style for your environment that has minimal relative gains and can still be obtained in D or ECO. A skilled driver can drive the LEAF the same way you do without ever using the neutral switch and get the same results because there is always a neutral spot on the pedal. The LEAF regen is so easy to manipulate because it is so weak. Putting that aside if you live in SF your theory is invalid because you need all the regen you can get because of the terrain and it is stil not strong enough. On the other end of the spectrum is also a extreme group of folks that creep to a slow agonizing speed and coast to each light slowing traffic and holding people to idle and waste gas at missed lights, they are some of the most frustrating hypermiler drivers around and I certainly won't ever be part of the old school Prius pulse and glide crowd. If they could push their cars from light to light they would. It is best to use what works for you and what you are comfortable with but constantly toggling the car to neutral will shorten the switch life, that is a mechanical fact. The switch may last 500 years or less than the life of the car but the wear is increased because there are moving parts with friction, not to mention they are made by Nissan. I often "coast" down steep grades and never use "N" where one could actually loose efficiency to exponential wind drag instead of using regen at a slower constant speed. I read a Nissan TSB that said they log the number of neutral cycles ont the LEAF computer and if they are over 12 a day at speeds over 10 MPH it voids the warranty on the shifter

Lol, more BS! Keep the stories coming as they are entertaining.

 

[mkjayakumar]

I see EVDRIVER's point in the Bay area with lots of hills. Over here in Dallas the only hills are the overpasses..

 

[dgpcolorado]

Interesting discussion. My experience is more like EVDRIVER because my terrain undulates with a mixture of steep hills and sharp curves. Only at the bottom of my biggest hill, with a long flat stretch then a rise, is it useful to shift to neutral, assuming no Sheriff's officers are present. For the rest, feathering the A pedal in ECO allows me to control speed via power/regen or zero power for brief coasting. But if I tried to shift to N each time I wanted to coast a bit I'd be shifting every few seconds: quite impractical. My complex terrain is very different from flatland or stop-and-go driving (only one stoplight in my county).

ECO, with its fixed power settings and stretched power mapping is, by far, the most efficient way to fine tune my power/speed to the terrain. The idea that D is better because of lower regen is a bit mystifying since one can choose any regen level in ECO, from zero up to the maximum allowed. Assuming that one uses the energy screen or add-on meter to measure it, I suppose. (Since I don't deal with traffic, monitoring the energy screen isn't a distraction or safety issue like it might be in some congested areas. Life is more peaceful here.)

 

[TickTock]

TomT, what year is your Leaf? Mine is 2011. My code averages the power over each second so no noise. How hard would it be to get Lincomatic to add a longer averaging interval? No CC or radio, etc (power does go to zero once stopped).

I used the shift to Reverse trick. I'll try the other way tonight.

TickTock, how are you calculating kW? I'm just multiplying packvolts * packamps. I don't do any averaging .. just instantaneous value updated about every 250ms. I get the same low 0-.2kW readings whether coasting in neutral (via reverse trick) or just sitting in my driveway.

I coasted in N for .5 miles and according to the LEAF App I used 18 Whs.

That is consistent. Assuming you took about a minute to travel that 0.5 miles, this would correspond to a little over 1kW.
(sorry for the late response - this thread dropped off my radar (New Posts query) so I didn't notice the activity)

 

[TickTock]

Shifting into "N" removes all drive signals from the IGBT's in the inverter, effectively free-wheeling the motor. It does not "fake" anything! It's no different than when stopped in drive with no pedal action.

The "house" loads in the LEAF are substantial, and of course continue even when you are in "N".

As TomT mentioned, the LEAF measures power in/out of the battery with a hall-effect current meter, and it is subject to drift, offset errors, and is generally inaccurate at low currents, so don't assume because the LBC (Battery Controller) reports more draw than you expect in "N", that the draw is real.

-Phil

The reason I think this draw is real is once the car actually comes to a full stop, the power drops down to near zero (<0.2kWh typ) - suddenly. It is ~1.2kW even during the last few feet of movement.
(sorry for the late response - this thread dropped off my radar (New Posts query) so I didn't notice the activity)

 

[TickTock]

I coasted in N for .5 miles and according to the LEAF App I used 18 Whs.

That is consistent. Assuming you took about a minute to travel that 0.5 miles, this would correspond to a little over 1kW.
(sorry for the late response - this thread dropped off my radar (New Posts query) so I didn't notice the activity)

BTW, just to put things in perspective, that 18Wh is the same amount of energy I measured that it takes to accelerate from rest to 60mph.

 

[ttweed]

What seems crazy to me is that anyone would give up one of the 3 primary elements to control the car (steering, brakes, and accelerator) in the name of stretching your range. Driving a car is serious, risky business, and we do it so much we become nonchalant about it, but the possibility of an accident is ever-present--the unexpected DOES happen. No amount of "economy" could convince me to disengage the accelerator when it might be needed at a moment's notice. Saving thousands of kWh's would not be worth wrecking the car, or inflicting bodily injury on myself or others.

You may believe that you could quickly throw the shift lever and get back in gear in an emergency, but the reality is that things may happen too fast, you may not react well in the milliseconds available, you may miss the lever on your first reach, and at the same time, you will have only one hand on the wheel when you are required to make some massive steering effort in a hurry to avoid something, further impairing your control of the car. The fact that you may actually need to speed up immediately to get out of a situation, or need to get back on the accelerator in a hurry to recover from a skid (by shifting weight to the rear in an oversteering situation) is being given scant attention here. It's just not worth taking such a chance when you are in charge of a 3,000 lb. hunk of metal hurtling down a road. Please think about all the possible consequences before you make coasting downhill for long stretches at high speed a habit.

TT