Leaf Service Manual (1-Day Subscription?)

[thimel]

Can someone who has the service manual use it to figure out how regenerative braking is done with the brake pedal?

Some time ago in another thread, someone who took a training course said that pressing the brake pedal first applied the friction brakes, then did regeneration and then more friction.

The owners manual on page EV-8 says "The brake pedal should be used to slow or stop the vehicle depending on traffic or road conditions. The vehicle brakes are not affected by regenerative brake system operation." To me this means that the brake pedal only applies friction brakes. I'm hoping this is just a bad translation but would like to know for sure how it works.

Assuming the brake pedal does some regenerative braking, is there a way to tell when it transitions to friction brakes? This is needed in order to learn how to minimize the use of the friction brakes.

Thanks

 

[Gonewild]

I was told that regen goes on first with a light touch and then you push harder the brakes kick in.

 

[TomT]

There is no reason to believe that it isn't pretty much the same as a hybrid or other such vehicles: Regenerative braking is used up to close to the point where the motor/charger can no longer provide the required brake power at which point the friction brakes come in to play. So, regenerative first followed by friction in increasing amounts. And, of course, friction only at a standing stop. The 6 times I drove a Leaf, the power indicators and feel pretty much confirmed this.

Can someone who has the service manual use it to figure out how regenerative braking is done with the brake pedal?

 

[EVDRIVER]

The regen is limited by Nissan's implementation as a result of making it seem more like a "normal" car. The regen always occurs first then the pads, which hit sooner than most factory EVs. This should not have anything to do with the charger.

 

[johnr]

The owners manual on page EV-8 says "The brake pedal should be used to slow or stop the vehicle depending on traffic or road conditions. The vehicle brakes are not affected by regenerative brake system operation." To me this means that the brake pedal only applies friction brakes. I'm hoping this is just a bad translation but would like to know for sure how it works.

Assuming the brake pedal does some regenerative braking, is there a way to tell when it transitions to friction brakes? This is needed in order to learn how to minimize the use of the friction brakes.

Thanks

This is from page 5-22 of the owners manual. Make of it what you will. I don't understand it myself:

When depressing the brake pedal, the braking pedal feel will not be smooth or may change when the cooperative regenerative brake system activates. However, the electronically controlled brake system is operating normally and this does not indicate a malfunction.

 

[garygid]

To understand how much Regen is "being done", and when, watch (safely) the energy usage display screen, where "Regen" should show up as 0 to 30 kW of power being produced.

Check the Regen amount:
1. as foot leaves the go-faster pedal
2. with foot-off, at various speeds
3. droping into "ECO" and back out, foot-off
4. gradually applying the "go-slower", both in "Eco" and not.

 

[EVDRIVER]

The owners manual on page EV-8 says "The brake pedal should be used to slow or stop the vehicle depending on traffic or road conditions. The vehicle brakes are not affected by regenerative brake system operation." To me this means that the brake pedal only applies friction brakes. I'm hoping this is just a bad translation but would like to know for sure how it works.

Assuming the brake pedal does some regenerative braking, is there a way to tell when it transitions to friction brakes? This is needed in order to learn how to minimize the use of the friction brakes.

Thanks

This is from page 5-22 of the owners manual. Make of it what you will. I don't understand it myself:

When depressing the brake pedal, the braking pedal feel will not be smooth or may change when the cooperative regenerative brake system activates. However, the electronically controlled brake system is operating normally and this does not indicate a malfunction.

This means the brakes will work if needed and braking may not always feel smooth. Everyone is reading too much into a poorly written manual and there is no mystery on how regen on an EV works.

 

[garygid]

We are trying to discuss and determine exactly how the Regen has been integrated into operation of the brake pedal on the LEAF.
NOT just discuss how "any" EV MIGHT operate.

Do you KNOW the LEAF's braking details?
If so, please educate us.

 

[AndyH]

Can someone who has the service manual use it to figure out how regenerative braking is done with the brake pedal?
<snip>
Thanks

I haven't spent enough time in the service manual to know all the details, but the system appears to be fully computer controlled and allows the 'friction brake system' and the 'regenerative brake system' to work together when they can (speed, brake pedal input, traction, etc.) and separately when they can't (speed, traction, malfunction, etc.). It doesn't look like a simple 'first inch of brake pedal travel is regen, then the friction brakes come in' - it appears that both friction and regen can be modulated throughout the braking process. Cool system!

From the service manual (section BR):

System Description
• An electrically-driven intelligent brake is a booster system that generates assist force by using an internal motor to operate a piston inside the master cylinder.
• When the brake pedal is depressed during driving, cooperative control of the braking force from the friction brake (regular brake) and the regenerative brake from the traction motor is used.
• The system performs cooperative control of the regenerative brake and friction brake (same brake as in conventional vehicles) and enables highly efficient energy recovery.
• The fluid pressure which is applied to each brake caliper is controlled according to the amount of traction motor regeneration.
• The amount of brake pedal operation is detected by the pedal stroke sensor, and sent to the control module of the electrically-driven intelligent brake unit.
• Based on the commands from the control module of the electrically-driven intelligent brake unit, the motor inside the electrically-driven intelligent brake unit is operated and presses the master cylinder piston.
• Pressing the master cylinder piston, and brake fluid is sent to the ABS actuator and electric unit (control unit).

• When there is a malfunction in the power system of the electrically-driven intelligent brake unit (no voltage is generated), voltage is temporarily supplied to the electrically-driven intelligent brake unit from the brake power supply backup unit. At the same time, the brake warning lamp (red) and brake system warning lamp (yellow) turn ON, and the warning buzzer sounds.

• A fail-safe function is available and is activated when a system malfunction occurs.

It's not a Zenn and not a Prius - no surprise there! :lol:

 

[LEAFer]

... it appears that both friction and regen can be modulated throughout the braking process. Cool system!
It's not a Zenn and not a Prius - no surprise there! :lol:

Yeah, but as a driver I would like to minimize the use of friction braking while maximizing regen use. So ... I hope the system (and the optimization) is easy to learn ... without requiring a lot of attention-diverting effort from me. :|

 

[AndyH]

... it appears that both friction and regen can be modulated throughout the braking process. Cool system!
It's not a Zenn and not a Prius - no surprise there! :lol:

Yeah, but as a driver I would like to minimize the use of friction braking while maximizing regen use. So ... I hope the system (and the optimization) is easy to learn ... without requiring a lot of attention-diverting effort from me. :|

It's out of your hands...er feet, LEAFer - the computer appears to be doing all the modulation and friction/regen mixing based on pedal force, battery state of charge, ABS status, traction, etc. etc. As I said - there doesn't appear to be a 'regen zone' and a 'friction zone' one can learn.

 

[LEAFer]

Too bad Maybe they should stick to the simpler Tesla philosophy: Go Pedal = accelerate, coast and regen; Brake Pedal: apply friction brakes. Driver does all the choosing. (Traction Control (on Go Pedal) and ABS (on Brake Pedal) take priority if situation makes it necessary.)


( I like the "It's out of your hands...er feet," :lol: )

 

[garygid]

So, we still do not know, from the book-learning, if one can gradually increase (an decrease, or "modulate") the Regen BEFORE any friction braking is applied?

 

[evnow]

Too bad Maybe they should stick to the simpler Tesla philosophy: Go Pedal = accelerate, coast and regen; Brake Pedal: apply friction brakes. Driver does all the choosing. (Traction Control (on Go Pedal) and ABS (on Brake Pedal) take priority if situation makes it necessary.)

There is always going to be this - designed for mainstream vs designed for enthusiasts. Leaf is designed for the mainstream.

May be n a couple of years enthusiasts will get theirs ... infinity or a different sports model. May be even a GTR EV to take on Tesla ;-)

 

[LEAFer]

The way braking works on Tesla has nothing to do with main-stream versus enthusiast. I don't see one or the other (type of car) from preventing use of either method. I just think the Tesla method is the simpler and very easy to learn and the "clearer" of the two. No-touch-brake = no-rub-pads.

If the LEAF were to make a VERY clear distinction between regen versus friction brake, that would be fine too. I'm simply the type that wants to know when friction brakes are in use versus how I can maximize regen. The "distinction" could be one of several things: pedal force feedback, an unobtrusive indicator (led on dash), etc.

 

[evnow]

I just think the Tesla method is the simpler and very easy to learn and the "clearer" of the two.

Mainstream users don't want to learn how to break. Regen should happen on its own in the most efficient way.

BTW, we have been through this regen or not on releasing accelerator pedal before. Infact very long and contentious threads. Don't want to start that again. Suffice to say there is more than one valid approach - and what is simpler or better is a matter of opinion.

 

[garygid]

But, we still do not know how the LEAF "merges" friction and Regen braking.

 

[evnow]

But, we still do not know how the LEAF "merges" friction and Regen braking.

Sounds "automagically". Essential they have some logic that takes into account the break press & road conditions etc.

 

[AndyH]

So, we still do not know, from the book-learning, if one can gradually increase (an decrease, or "modulate") the Regen BEFORE any friction braking is applied?

Your answer is in the post above, Gary - in Nissan's words. I know that you have a copy of the service manual - feel free to brak..er..break it open.

The car's systems are integrated and communicate via a network. The friction brake boost system is electric - there's a motor in the master cylinder controlled by the brake computer. The car uses the anti-lock brake/traction control system (sensors on the wheels), inputs from the brake pedal, battery state of charge, inverter temperature, etc. to determine how much regen is available.

The anti-lock/traction control system can apply different brake force to each of the four wheels. Regen only works on the front wheels - and may not act on both wheels with the same bias.

The computer and sensors are doing all the math. We get four inputs - foot on the brake pedal (or not), and Eco mode (or not). After that, the computer decides how much regen to use at each interval of time and additionally sends hydraulic brake force to each of the four wheels independently. The book also talks about reducing or removing hydraulic brake force if more regen can be applied - like when the car stops sliding. It sounds like it's a very fluid mixing - not at all like the 'zone one, zone two' view we've talked about in the past.

The brake control system section of the manual has 156 pages. The traction control system uses the steering angle sensor, the four wheel-slip sensors, a g-force sensor so the car can feel wheel spin, oversteer/understeer, side slip and yaw rate - and it'll adjust braking and power delivery as needed to keep control.

I think ABS and traction control are nice things to have, and at the end of the day a successful trip is one where all the occupants exit the cabin in the same number of pieces they were in when they entered - and for that I don't need to adjust regen.

Back on topic... This is the least expensive service manual I've ever purchased for a car - and it's one of the most intuitive and complete that I've used. It's well worth the $20 and few minutes it takes to download the information!

edit...added info, lowered snarky index a notch as it's actually silly to expect a software guy to read the manual before the crash...

 

[evnow]

Back on topic... This is the least expensive service manual I've ever purchased for a car - and it's one of the most intuitive and complete that I've used. It's well worth the $20 and few minutes it takes to download the information!

I'm waiting to see if more may be added later ... unlikely ?