Regenerative Braking Drive Modes Gimmicky?

[JoulesThief]

[
But 'NOW' you are burning the brakes more. Which is cheaper? The savings in Charging or the cost to replace a set of brakes?

As Neil mentioned, the way BEV's and hybrids are set up, pressing the brake pedal is supposed to use up regen first. The friction pads are supposed to be invoked only if the desired stopping force is more than the available regen.

There are folks with high-mileage Prii who have never replaced their brake pads.

Actually I was comparing running in 'B' mode vs coasting and using your own judgement to brake smoothly.
The computer can easily decide to run the car down without invoking the brakes often, but can the human?

But even that in mind, I'm a city driver. LOTS of stop / go. (Very little freeway unfortunately). So I believe it would be better for me to let the car regen the energy instead of always using the brake.

Someone is feeding you bad information, again. Using the brake pedal does regenerate. Looking at your gauges is proof, while stepping on the brake pedal. Your posts read like an "Error 404".

 

[bizzle]

[
But 'NOW' you are burning the brakes more. Which is cheaper? The savings in Charging or the cost to replace a set of brakes?

As Neil mentioned, the way BEV's and hybrids are set up, pressing the brake pedal is supposed to use up regen first. The friction pads are supposed to be invoked only if the desired stopping force is more than the available regen.

There are folks with high-mileage Prii who have never replaced their brake pads.

Actually I was comparing running in 'B' mode vs coasting and using your own judgement to brake smoothly.
The computer can easily decide to run the car down without invoking the brakes often, but can the human?

But even that in mind, I'm a city driver. LOTS of stop / go. (Very little freeway unfortunately). So I believe it would be better for me to let the car regen the energy instead of always using the brake.

I'll tell you where I think this concept applies: shifting into B mode while de-celerating is likely more efficient than foot braking. Not driving around in B, rather shifting into B as you slowly coast into the stop. You could match the efficiency with your foot, but it's more difficult to be as precise and not accidentally press too lightly or too hard.

The order from most to least efficient driving styles seems to go like this:
Driving in D mode, braking in B mode
Driving in D mode, braking with foot in D mode
Driving in B mode, braking with/out foot in B mode

 

[forbin404]

[
The order from most to least efficient driving styles seems to go like this:
Driving in D mode, braking in B mode
Driving in D mode, braking with foot in D mode
Driving in B mode, braking with/out foot in B mode

Well at least that can be done easily without much thought. Especially if you used to drive a stick.

 

[bizzle]

I think a number of people here have written they use B mode like I do, which is to say similar to downshifting a manual.

 

[cctop]

The order from most to least efficient driving styles seems to go like this:
Driving in D mode, braking in B mode
Driving in D mode, braking with foot in D mode
Driving in B mode, braking with/out foot in B mode

As I mentioned earlier in the thread, I get roughly 20% more efficiency keeping the car in B mode than in D mode.

That's for an 8-mile commute across San Francisco of which maybe three blocks are level ground so I'm never coasting.

 

[NeilBlanchard]

But 'NOW' you are burning the brakes more. Which is cheaper? The savings in Charging or the cost to replace a set of brakes?

No, all the regen is integrated into the brake pedal.

 

[forbin404]

But 'NOW' you are burning the brakes more. Which is cheaper? The savings in Charging or the cost to replace a set of brakes?

No, all the regen is integrated into the brake pedal.

Let me describe:

You are going 60 and in D. You let the pedal go, you coast around 60 (With some air resistance). You see people stopped ahead. You push the pedal while going 60. Do you push it EXACTLY what you need to activate the regen only or do you push it a little too hard and activate the brakes (It's not all regen).

You are going 60 and in B. You let the pedal go (And the car JERKS..cause it's in B). You see people stopped ahead. Since you are in B you are probably going around 45 by the time you reach them. (B isn't as harsh at high speeds I noticed). You push the pedal at about 45. If you push it the same way and activate the brakes, is the brakes rubbing at 45 going to wear them down LESS than at 60?

Or you are you implying that you always break the exact amount needed to only kick in regen. And if this is true why not just drive in D3 and if you want to 'coast' just keep your foot on the pedal slightly? It's not like you are using any extra energy keeping the foot on the pedal, look at the meter, you have the pedal slightly down and you are at ZERO on the charging tach while in D3 mode (or D2 or D1)

 

[JoulesThief]

But 'NOW' you are burning the brakes more. Which is cheaper? The savings in Charging or the cost to replace a set of brakes?

No, all the regen is integrated into the brake pedal.

Let me describe:

You are going 60 and in D. You let the pedal go, you coast around 60 (With some air resistance). You see people stopped ahead. You push the pedal while going 60. Do you push it EXACTLY what you need to activate the regen only or do you push it a little too hard and activate the brakes (It's not all regen).

You are going 60 and in B. You let the pedal go (And the car JERKS..cause it's in B). You see people stopped ahead. Since you are in B you are probably going around 45 by the time you reach them. (B isn't as harsh at high speeds I noticed). You push the pedal at about 45. If you push it the same way and activate the brakes, is the brakes rubbing at 45 going to wear them down LESS than at 60?

Or you are you implying that you always break the exact amount needed to only kick in regen. And if this is true why not just drive in D3 and if you want to 'coast' just keep your foot on the pedal slightly? It's not like you are using any extra energy keeping the foot on the pedal, look at the meter, you have the pedal slightly down and you are at ZERO on the charging tach while in D3 mode (or D2 or D1)

:mrgreen: Where did you learn to drive? IMHO, you need more lessons.

If you never peg the needle in the green, you'll hardly ever apply the brake pads, it will be all regen. The key is to braking far enough in advance, so you never peg the needle in the green. Step on the brake pedal harder, once the needle is pegged in the green, and you will use brake pads also to slow down.

Operate the brakes so you never peg the needle in the green range, always at less than pegged green, by braking far enough in advance.

You'll never be able to achieve this if you drive with a "herd mentality" frame of mind and operation, doing what everyone else does. Otherwise defined as "mindless driving". These are the types of drivers that get in chain reaction braking accidents.

 

[mvolta]

It is simple physics

What are the causes of deceleration when driving a car?

1. air resistance
2. friction from the wheel to the ground

If you accelerate to 60 and let go of the pedal you will slow down because of those 2 forces

In D mode: Only those 2 forces slow you down

In D1/2/3 and B mode: those 2 forces + the regenerative mechanism

whats cool about B mode is that you can control the regenerative mechanism with your foot on the gas pedal. B mode by itself will put you at the strongest regenerative mode, but you can accentuate the strength of the braking force by using your foot on the pedal. This is very convenient when street driving/traffic , going from light to light where you have many deceleration. I almost never have to use the brake pedal anymore using B mode. On the highway you use D mode because you do not need to decelerate at all on the highway until you exit in which i always switch to B mode as im exiting and its hella fun to do. I enjoy this new driving method for the EV. its cool.



if you think about energy utilization

you use EV energy when:

you accelerate + maintain constant velocity (fight the air resistance and friction)

when you slow down ultimately the best energy scenario would be to let go of the gas pedal and let the car decelerate to a stop. this doesn't work obviously because the braking process would be slow and driving is a more dynamic process.

SO this leads us to the main issue: whats the whole point of this regenerative mechanism?

To save the energy normally lost in the dynamic nature of our driving system. aka stopping at a light, in heavy traffic, or any driving process that requires alot of fast, on-demand braking. That is why you WILL notice our EV cars work ******* great in heavy traffic while for gas cars it is really ****** for their mpg because they waste all the energy to the friction on the brake pads.

 

[NeilBlanchard]

Regen can only recover some of the energy - so it is better than friction brakes, but worse than coasting.

 

[Verkehr]

Regen is better than coasting for recovering potential energy (going down hills) where coasting will result in higher average speed and more aero losses, though.

 

[NeilBlanchard]

Regen is better than coasting for recovering potential energy (going down hills) where coasting will result in higher average speed and more aero losses, though.

It all depends on what you need to do: if you want to carry speed (and you can) then coasting is best. Regen should only be used when you need to slow down.

Coasting has the lowest loss possible - and uses the kinetic energy to move the car forward. Regen can never regain all the energy (by definition) so it is better than friction brakes - but it cannot substitute for coasting.

Aero losses will always happen, so that is a red herring.

The other aspect of coasting is that you accelerate less - so you use significantly less energy, and then use the kinetic energy you have "invested" in the moving car in the best way possible. In B mode, you accelerate and then regen, so you use more energy, then lose more.

 

[Verkehr]

Regen is better than coasting for recovering potential energy (going down hills) where coasting will result in higher average speed and more aero losses, though.

It all depends on what you need to do: if you want to carry speed (and you can) then coasting is best. Regen should only be used when you need to slow down.

Coasting has the lowest loss possible - and uses the kinetic energy to move the car forward. Regen can never regain all the energy (by definition) so it is better than friction brakes - but it cannot substitute for coasting.

Aero losses will always happen, so that is a red herring.

The other aspect of coasting is that you accelerate less - so you use significantly less energy, and then use the kinetic energy you have "invested" in the moving car in the best way possible. In B mode, you accelerate and then regen, so you use more energy, then lose more.

I don't disagree. Let me restate that I was referring only to "going down hills where coasting will result in higher average speed" e.g. any steep hill since one obviously can't alter the topography with their driving style.

I thought of another real world coasting-buster scenario: no traffic, travelling 55 mph, light turns red 1/8 mile up the road (or whatever particular distance a 55 mph e-golf would coast for). It's a long light... coasting all the way up without touching the brake is less efficient than regen braking hard and then travelling at a slow rate (~15 mph) before coasting to a stop; every moment spent at higher speed is more kJ being used to heat the air. Regen losses are quickly overcome with less energy lost in the air. Just a way of lowering average speed with little effect on travel time.

 

[xchopp]

I feel the Regenerative Braking Drive Modes are gimmicky.

I love these modes -- especially B, it is so smooth!

 

[xchopp]

You are going 60 and in B. You let the pedal go (And the car JERKS..cause it's in B).

My e-Golf never "jerks" while driving in B mode -- it is as SMOOTH AS BUTTER. It would only jerk that if you shifted from D to B at speed.

 

[forbin404]

You are going 60 and in B. You let the pedal go (And the car JERKS..cause it's in B).

My e-Golf never "jerks" while driving in B mode -- it is as SMOOTH AS BUTTER. It would only jerk that if you shifted from D to B at speed.

Heh then is your B mode broken? haha

Mine makes my passenger heads move forward. They started to complain

 

[JoulesThief]

You are going 60 and in B. You let the pedal go (And the car JERKS..cause it's in B).

My e-Golf never "jerks" while driving in B mode -- it is as SMOOTH AS BUTTER. It would only jerk that if you shifted from D to B at speed.

Heh then is your B mode broken? haha

Mine makes my passenger heads move forward. They started to complain

Learn to drive smoother with more subtle changes, slower on and off the throttle, and that problem will go away. Drive smooth.

 

[Unbeliever]

Mine makes my passenger heads move forward. They started to complain

The problem is in your right foot. Ease off the pedal, don't fall off the pedal.

 

[forbin404]

Mine makes my passenger heads move forward. They started to complain

The problem is in your right foot. Ease off the pedal, don't fall off the pedal.

Lol, I was making a statement, and the other person was rebutting that it doesn't happen.

Haha

 

[JoulesThief]

Mine makes my passenger heads move forward. They started to complain

The problem is in your right foot. Ease off the pedal, don't fall off the pedal.

Lol, I was making a statement, and the other person was rebutting that it doesn't happen.

Haha

Your passenger was complaining that you have poor operator driving skills. Haha! Basically, you suck at throttle control. Haha! Then you complain about the results, as does your passenger. Haha! :roll:

Lord forgive me for feeling bad, stooping so low, down to Error 404's level. He was in need of a taste of his own medicine, taunting others with "Haha" posts.