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Re: Have B Mode as Deflaut Drive Mode

Posted: Thu Dec 21, 2017 1:41 pm
by nerys
I disagree. When i lightly brake in D versus B there is a significant difference in regen. Its like there is a software cap on regen amount in D mode that is particularly nasty when cold. Almost no regen at all.

On top of this in D mode i cant feather the speed controller since i have to move my foot to the brake pedal.

In b mode i keep my foot on the acceleration pedal and feather it to control the amount of regen versus coast down for each individual stopping scenario.

I can not do this in d mode since i have to move my foot to the brake pedal.

Re: Have B Mode as Default Drive Mode?

Posted: Thu Dec 21, 2017 1:46 pm
by LeftieBiker
The OP (cmwade77) was claiming better range due to using B mode. It then came to light that he was driving downhill to work, and claiming the benefit from that was from using B mode. Nerys is now chiming in that gravity doesn't add range or energy to the pack, only B mode does that. I blame this on standardized testing...

Anyway, a short summary:

* When you drive downhill, gravity pulls the car along the road, eliminating some or all of the need for using the motor. The car acquires more momentum, and thus more kinetic energy. This increases range, especially if you don't apply the friction brakes, but also even if you do. Regenerative braking, whether from B mode, Eco mode, or from just lightly applying the brakes, "harvests" the additional energy provided by gravity and sends it to the pack. Heat and friction losses in the motor/generator and electronic controls, along with chemical inefficiency in the pack, result in roughly 40% of this energy being returned to the car as kinetic energy. Coasting, OTOH, has only the same friction and aerodynamic losses the car is experiencing anyway, and is so much, much closer to 100% efficient. What B mode does is collect some of the energy that is normally lost as heat in stop and go driving. It is NOT as efficient as coasting, but it is safer and more convenient.

That's enough from me.

Re: Have B Mode as Deflaut Drive Mode

Posted: Thu Dec 21, 2017 1:51 pm
by nerys
Yes standardized education does explain a lot of this

Book knowledge without practical experience

Gravity adds no energy to the car gravity has the ability to add potential energy to the car to realize that potential energy you must permit the car to accelerate to actually transfer that energy to the car's inertia but we have this little thing called speed limits and stop signs and they tend to be pretty low and they tend to exist the bottom of these Hills

The purpose of regeneration is to put energy back into the battery is low in the car down that otherwise would have been wasted in your brake pads

It is that simple it's not complicated it's rather basic physics

Now sure if you can find a nice big hill with an unlimited speed limit and no pedestrians and no the cars and no stop signs or other traffic control devices and no cop to pull you over sure then you can allow gravity to accelerate your car as best it can and Coast to your heart's content

For the rest of us there speed limits in stop signs and there's practical limitations to how far you can Coast down without pissing off the people behind you so much that they want to shoot your brains out

An optimal Coast down profile for maximum efficiency is completely impractical for 99% of us and will get you either shot Road Rage or ticketed

For the other 99% of us does regenerative braking

Re: Have B Mode as Deflaut Drive Mode

Posted: Thu Dec 21, 2017 2:12 pm
by Nubo
It's really quite simple.

Most if not all would agree:
- coasting is more efficient than regen
- regen is more efficient than friction brakes
- friction brakes are more efficient than crashing

And the simple truth is you can exploit that heirarchy in either drive mode.

B simply gives you a higher *maximum* regen if and when you want it. But you can reduce the amount of regen at any time by moving the pedal as desired.

So, in practice, B is the most versatile while still allowing you to achieve the best combination of coasting/regen/brakes to suit the driving condition. I.e., just as good as an equally-motivated driver using D mode. The throttle mapping in Eco mode allows more precision here.

The only driving situations where B is a detriment are either:

A) cruise-control where regen is automatically invoked above what you would otherwise use. E.g.: you would have coasted instead of using regen.

B) you don't have the dexterity or are not inclined to manage regen as needed with the accelerator pedal.

Re: Have B Mode as Deflaut Drive Mode

Posted: Thu Dec 21, 2017 2:12 pm
by LeftieBiker
This time I mean it. I give up.

Re: Have B Mode as Deflaut Drive Mode

Posted: Thu Dec 21, 2017 4:59 pm
by nerys
It's usually a pretty good idea to stop when you're wrong that's usually the smart move

Re: Have B Mode as Deflaut Drive Mode

Posted: Fri Dec 22, 2017 2:17 pm
by cmwade77
LeftieBiker wrote:
I have about a 20 mile commute and there have been times where I actually have had the battery percentage be higher than when I left by using the B mode. Only by a percentage point or two, but still higher and yes I know that isn't always the normal, but it is a good example of why it would be nice to be able to set B mode as the default drive mode.


This can only be true if you are driving downhill. It is literally against the laws of physics for it to be true in any other case - except for maybe being pushed by traffic behind you... ;-)

Don't ask me, all I can say is what happened......although I will admit the majority of the drive back is downhill (although not steep).