Down hill gental bake or coast? for recharge

[DonoraiL]

I live in Los Angeles, CA USA area and I go down some long hills. I have been lightly braking thinking that I am engaging the generator function of the motor (because of the indication on the dash), but not wearing the brake pads, but I wonder if the car automatically regenerates while coasting or maybe in "low" gear. Anyone know for sure the best way to recoup energy on long down hills?

 

[GTOGreg]

I live in Los Angeles, CA USA area and I go down some long hills. I have been lightly braking thinking that I am engaging the generator function of the motor (because of the indication on the dash), but not wearing the brake pads, but I wonder if the car automatically regenerates while coasting or maybe in "low" gear. Anyone know for sure the best way to recoup energy on long down hills?

Ride the brakes...that's what I do. I gain +8 on my little "video game" every morning coming down my grade. L is an engine brake and if anything cuts into your energy efficiency...you won't regenerate as such. I thought using L might provide some efficiency coming back up the hill at the end of my commute, but i haven't found it to be any more efficient than just keeping it in drive.

Now, if you're starting out with a full charge and have no place to store the regen, then it might make sense to "downshift" to L and preserve some brake wear while offsetting the distance to get down the hill.

 

[yakers]

Thanks for the response, I had the same question. So I will keep light pressure on the brake on long downhills (I also live in LA area) and skip trying to figure out if low has any usefullness. Just one thing, I thought if the brake is pressed lightly the brake pads don't engage and I didn't think regenerative braking wore out anything, am I wrong?

 

[danholl]

Thanks for the response, I had the same question. So I will keep light pressure on the brake on long downhills (I also live in LA area) and skip trying to figure out if low has any usefullness. Just one thing, I thought if the brake is pressed lightly the brake pads don't engage and I didn't think regenerative braking wore out anything, am I wrong?

Pressing the brake part way brakes with regen. Brake pads don't apply until pedal is further depressed. It usually obvious when they engage as much stronger braking occurs. That is why it is recommended to start gently braking a ways before you want to stop. Don't roar up to the red light or stop sign and then Jam on the brakes. Then you get no regen and do wear out your brake pads.

 

[GTOGreg]

Thanks for the response, I had the same question. So I will keep light pressure on the brake on long downhills (I also live in LA area) and skip trying to figure out if low has any usefullness. Just one thing, I thought if the brake is pressed lightly the brake pads don't engage and I didn't think regenerative braking wore out anything, am I wrong?

Pressing the brake part way brakes with regen. Brake pads don't apply until pedal is further depressed. It usually obvious when they engage as much stronger braking occurs. That is why it is recommended to start gently braking a ways before you want to stop. Don't roar up to the red light or stop sign and then Jam on the brakes. Then you get no regen and do wear out your brake pads.

+1

You'll get the hang of braking early. It isn't going to wear any more than the late brake/high friction stop. It will feel natural...and if you're applying too much brake you will stop

 

[dwf123]

Gentlemen,
Check the owner's manual. "D" Drive will begin regenerating when you take your foot off the accelerator. "L" Low increases generation and slows the auto down faster. Lightly pressing the brake adds to the regeneration when in D or L. "N" Neutral is pure coasting. In ICE automobiles the brake pads lightly touch the rotors or drums during all periods of driving and is why even in neutral a car will slow down. In the FEE the brake pads are completely disengaged.

I live in RI and commute over two very tall bridges daily. I have experimented with using drive and low on the down side of the bridges and coasting in neutral. By far the fastest way to regenerate is using neutral and not using any energy to operate. Time your crest on the hill and slip into neutral and your car will coast many miles. If you begin traveling too fast slip into drive or low and it will slow down considerably. Using neutral to approach stop lights is another great advantage. Just be careful of who is behind you, because the brake lights do not come on. I really enjoy this slight re-creation of a manual transmission and it keeps my watts per mile average pretty solid.

Kindly, Wood Foss

 

[Yoyogee]

No brake lights in Neutral!!!! (That sounds like a class action lawsuit in waiting). Thanks for the tips!

 

[danholl]

No cars have brake lights on when in neutral and brakes are not applied.

All cars including the EV have brake lights when you step on the brakes no matter what gear you are in including neutral.

It is not recommended by any manufacturer that you put the car in neutral to coast.

 

[BuddhaGorilla]

Anyone else doing the neutral for downhill coasting? I have a lot of low grade hills where I can preserve my speed in neutral but staying in drive w/ regeneration slows me down too much and I need to lightly press the accelerator.

Anything wrong with coasting in neutral?

 

[DavidJohnson]

I don't recommend anyone operate their vehicle (any kind of vehicle) in neutral. It seems like you're taking one of the main controls away from your vehicle. I can't see where the benefit outways the potential disaster. Just my humble opinion... I'm a mechanical engineer, just not in the automotive industry.

 

[WattsUp]

Plus, there is no regen in Neutral, so you are "losing" energy if you coast down a hill in Neutral. You could have instead been using gravity to charge your battery (which will offset the energy needed to go back up the hill later, presumably).

It also makes no sense to cruise up to stoplights or other level-ground stops in Neutral. You are slowing down anyway, and should be using gentle regen to do so, instead of the mechanical brakes. Again, lost charging opportunity, and unnecessary brake wear.

All this, plus the fact that operating the vehicle in Neutral is not particularly smart, from a safety standpoint, as has been mentioned.

 

[vetboy45]

Are the brake lights activated by an accelerometer or only by pressure on the pedal? If not attached to an accelerometer, it seems to me low would be dangerous.

 

[davideos]

I'm pretty sure the brake light works regardless of what gear you are in. However, regen only works when the gear is "D" or "L". You will notice that if you brake in neutral, you will not get a "score" for how well you did on braking. I believe the reason is neutral disengages the motor from the wheels and the regen is actually done by the motor itself. Disengage the motor, no regen braking.
As for neutral being more efficient, it is....provided you are not braking...remember, no regen if braking in neutral. The reason you can go further in neutral while coasting is because there is no drag from the motor or gearbox or if the motor is doing a little bit of regen. Now if you find yourself going too fast in neutral, then you should pop yourself back into drive before applying the brake. Eventhough the brake coach says 100% regen, you don't get all that energy in your battery; all that means is that the brake pads didn't have to touch the disk. Recapturing kinetic energy and putting it into your battery has to overcome the mechanical loss from tires to gearbox to motor to recharge circuit to battery's efficientcy at storing a charge.

Anyway, long story short, I would coast.

 

[WattsUp]

As I and others have pointed out, driving in Neutral is not smart. (Check back in the previous articles in this thread, as well as others.) The marginal increase in efficiency (if it even exists) is not worth the decrease in vehicle control. In an emergency, would you rather be fumbling with the gear shift, or accelerating out of the way if needed (perhaps with split seconds to spare)? Driving in Neutral is not advised under any circumstances.

Also, I don't think the question about the tail lamps was whether they would somehow become disabled, but rather whether or not the heavy regen mode (driving in L) automatically lights the tail lamps as if the driver was depressing the brake pedal. The answer is no, engaging the heavy regen mode (by releasing the accelerator pedal) does not automatically light the tail lamps. In the FFE, the tail lamps only light when the brake pedal is depressed.

That's just the FFE though, not a standard behavior for all EVs. With the Telsa Model S, for example, its heavy regen mode does light the tail lamps.

 

[dmen]

Shifting from neutral to drive for urgent maneuvering in FFE should be no slower than shifting from 5th gear to 4th or 3rd in a manual transmission vehicle. Such would be necessary to quickly accelerate if one had been coasting in anticipation of a gradual stop, then suddenly needed evasive maneuvering. Nor should it be any slower than an automatic with turbo lag like with my previous car, a turbo 4-cyl A4- if I was coasting and then mashed the accelerator pedal, the trans would downshift and there would be a 1/2 second that felt much longer before any real accel. Very unnerving when trying to hang a quick left with unexpected oncoming traffic for instance! Back to FFE, or any EV I suppose- the availability of immediate torque/accel when in D at a wide range of speeds makes it uniquely safe for the kinds of situations you are picturing, wattsup.
Anyway if choosing to coast in N (davideos is correct that coasting in N is more energy efficient than coasting in D), the driver should be savvy enough to keep the right hand on the selector handle ready to pop it into D or L should slowing or speeding be necessary. No fumbling necessary. I would hope the selector can't be accidentally moved to R when in forward motion!

 

[WattsUp]

... and manual transmission vehicles are probably a little less safe than automatics because of that very need to manually "manage" the gearbox.

And note that some of the other things you mention (turbo lag, automatic downshifts, etc.) are still predictable, machine behaviors. Sure, they may introduce some delay, but the car will still react no matter how flustered the driver becomes.

What I'm talking about is the potentially complete failure to react, or a substantial delay in reacting, due to a human being occupying what amounts to a "critical link in the drive train". Human beings are much less reliable than turbo compressors or automatic transmissions.

Not everyone is an expert driver. Not everyone will keep a perfect presence of mind when faced with a sudden emergency. No matter how savvy a vehicle operator one might feel themselves to be, they'll probably forget about being in Neutral when the truck loaded with steel pipes flips over in front of them. They could spend a confused second or two wondering why the accelerator isn't responding, possibly with dire consequences.

Anyway, I just feel that the recommendation to coast (at speed) in Neutral should not be made casually. You do it at your own risk. And, if you're driving around friends and family, do it at their risk as well, if you feel that is appropriate. If it was me, I wouldn't take the risk at all, for the marginal increase in efficiency. Something, arguably, this car is already very good at.

 

[dmen]

I think anyone who gets flustered for 2 seconds not remembering that they have been coasting in neutral for maybe a minute at most shouldn't be driving. Grandpa better retake the road test!

I see what you're trying to say. And I'll agree that someone who isn't comfortable with shifting gears while driving should NOT coast in N to improve efficiency.

But in the example you gave, the safest action would be to STOP. Even if swerving onto a shoulder to get out from behind the truck/ pipes, slowing down would be much more helpful than speeding up. When would you really need to urgently accelerate? Very rarely? I'm thinking of someone changing lanes into me, or a car coming out of a blind driveway as I approach, or a deer I see too late- all could arguably be handled by stopping/slowing rather than speeding ahead. I wouldn't be coasting in significant traffic nor on blind curves or residential streets, so only the deer seems like a possible situation while coasting. Whether or not I have to shift first, I'm not going to react fast enough in those kinds of split-second situations. This human has to do something, even if it's "just" moving my foot.

Coasting in neutral on rare occasions or not, we are ALL putting ourselves and our passengers at risk every time we drive no matter how safe we think we are.

 

[WattsUp]

We can agree to disagree.

I just personally think driving in Neutral is like riding your bike with no hands. Sure, you might do it a lot without anything bad happening, even think you're good enough to never make a mistake at it, but when it does go wrong (an unseen pebble in the road, some unplanned movement that knocks you off-balance, etc.) it will go really wrong. It's not that you're "too dopey" to otherwise ride a bike competently, or a "grandpa" with slow reactions... you're just human, and there are some mistakes you simply won't be able to overcome.

So, there's the safety issue, IMO. But, I also don't think that coasting in Neutral will make any significant difference to the range one can eek out of the FFE. You'd have to do it a lot, and over long distances.

Coasting up to stops in Neutral makes no sense. Instead, you should be using regen over the entire stopping stopping distance to recover the maximum amount of kenetic energy. That leaves only "coasting while driving" (i.e., not trying to stop) as a potential beneficial scenario, which realistically could only mean sustained downhill coasting. And, if you are going downhill, again, you should be trying to benefit from regen. If it's a steep enough hill, shift to L to maximize the benefits. If you coast, you'll only be losing the opportunity to regenerate.

There is just no convincing argument that driving in Neutral will unlock some sort of "untapped" efficiency with the FFE, or EVs in general, and no one in this forum should feel that it is a viable recommendation.

 

[WattsUp]

But in the example you gave, the safest action would be to STOP. Even if swerving onto a shoulder to get out from behind the truck/ pipes, slowing down would be much more helpful than speeding up. When would you really need to urgently accelerate? Very rarely?

You might need to get out of the way of the people behind you (who haven't noticed that the truck flipped over). My point is that you may need both options (slowing down and speeding up), and you may have only split seconds to execute them. Adding any more risk to the type of unpredictable situation is just not worth it, IMO, especially when there is hardly any benefit to be had (if any) from the added risk.

 

[dmen]

Yes, agree to disagree on the safety of neutral. Driving in cruise control, assuming your foot isn't held hovering over brake/accelerator the whole time, could be considered unsafe too.

Your example of the bike is not a fair comparison. Riding a bicycle with your feet off the pedals would be comparable. Even if the rider can't get his feet back on, he can still steer and stop. Neutral does not equal no control.

As for the gain in efficiency of coasting in neutral vs drive, sure it's small. But when someone wants or needs to push the range, all these little things add up. Driving a few miles under speed limit might be dangerous too but it will get you farther. So will rolling through stop signs. So will going a bit slower up a hill than down. So will leaving the heater off even though the windshield might start to fog. So will using the wipers less. You could and probably should choose to do none of these things but if you're trying to make it through the countryside to get to the next charger, they will help.

I will try to do some experimental driving to get a better sense of the difference.