regenerative braking

[dlew]

In Carwings, there is a section "My Driving Style". Under the section "electricity captured by regenerative braking", I have 1.9kHw and at level 3. Is there a special way to use the brakes to increase my kHw?

 

[EdmondLeaf]

IMHO level 3 is very good, In my recent history best was 2. I believe we using different driving technique I try to coast as much as possible and whenever is possible. Recently I managed 6.9 mkWh with the average speed about 45mph 60 miles trip. I try to use brake as little as possible because efficiency of energy capture is not 100%.

 

[PatricioEV]

I have a 3.9kwh and level 4 for the same figure, and all I can say is I use the shifter FREQUENTLY to coast in N or slow down in ECO so as not to touch the brake pedal. When I do brake, I try not to exceed the available regen bubbles. Otherwise, I don't drive in a particularly careful manner with this car. And I use the off-the-line torque as much as possible!

 

[TickTock]

Right. Avoiding the brake pedal all-together is the only sure-fire way. Every-time you touch the brake pedal, regardless of how gently you drive, the friction brakes are engaged (at least momentarily). However, you *can* minimize it. I hacked Gary's SOC meter so it chirps at me whenever friction brakes are applied (geiger-counter style proportional to the amount of energy being wasted with the friction brakes). It has definitely altered my braking style. I have learned that overshooting the target braking force a smidge and then backing off stops the application of friction the best. If you just slowly increase the brake force, the friction tends to stay on. Also, I've noted in the canbus logs that not only does application of friction waste heat, you get double-impacted because regeneration is reduced when friction is applied (exception during long downhill applications - regen can be made to stay at full along with friction if the brakes are applied long enough).

The highest I've ranked on CarWings is 4. However, I cannot figure out how the kWh number is related. I've had days with 5.6kWh but only ranked 3, and others with 2.2kWh and ranked 4.

Finally, don't be fooled into thinking you can feel the friction application. Before hacking my box, I though I could because there is a noticeable non-linearity in the brake response as you increase the braking force. I always thought that was friction being employed. Turns out the opposite. Friction started the moment I pressed the pedal and that non-linearity I was feeling appears to be related to entering max regen (although friction may or may not be engaged when you feel it).

 

[Nubo]

In Carwings, there is a section "My Driving Style". Under the section "electricity captured by regenerative braking", I have 1.9kHw and at level 3. Is there a special way to use the brakes to increase my kHw?

Regen, in and of itself, is not a goal. Efficient driving will produce different amounts of regen depending on the circumstances. Ideally, you'd never use it at all, since you are not recapturing 100% of the energy. I.e, coasting is more efficient than regenerative braking, which is more efficient than friction braking....

In the real world we have to slow down. But if you think further ahead you can minimize that necessity. Plenty of hypermiling advice to be found. I don't go to extremes, but I do tend to allow a greater following distance and try to anticipate lights, lane changes and lane-changers so that I'm not always having to pop on the brakes. I'm sure you've followed drivers at the opposite extreme -- constantly switching between gas and brake because they have an unnatural attraction to car bumpers. :roll:

 

[KeiJidosha]

Right. Avoiding the brake pedal all-together is the only sure-fire way. Every-time you touch the brake pedal, regardless of how gently you drive, the friction brakes are engaged (at least momentarily). However, you *can* minimize it. I hacked Gary's SOC meter so it chirps at me whenever friction brakes are applied (geiger-counter style proportional to the amount of energy being wasted with the friction brakes). It has definitely altered my braking style. I have learned that overshooting the target braking force a smidge and then backing off stops the application of friction the best. If you just slowly increase the brake force, the friction tends to stay on. Also, I've noted in the canbus logs that not only does application of friction waste heat, you get double-impacted because regeneration is reduced when friction is applied (exception during long downhill applications - regen can be made to stay at full along with friction if the brakes are applied long enough).

The highest I've ranked on CarWings is 4. However, I cannot figure out how the kWh number is related. I've had days with 5.6kWh but only ranked 3, and others with 2.2kWh and ranked 4.

Finally, don't be fooled into thinking you can feel the friction application. Before hacking my box, I though I could because there is a noticeable non-linearity in the brake response as you increase the braking force. I always thought that was friction being employed. Turns out the opposite. Friction started the moment I pressed the pedal and that non-linearity I was feeling appears to be related to entering max regen (although friction may or may not be engaged when you feel it).

The argument for right pedal regen, eloquently made.

 

[gbarry42]

I hacked Gary's SOC meter so it chirps at me whenever friction brakes are applied (geiger-counter style proportional to the amount of energy being wasted with the friction brakes).

NOW I have a reason to get one of those meters!

 

[KennyLewis]

I have been trying to compare ECO mode to Drive to see which gives the highest Miles per KW. Somewhere on this site I read that there are better results in Drive. It appears from CarWings data that I am actually getting a higher percentage of regen in Drive. I don't understand this. I am also getting higher Miles Per KW. The weather has gotten warmer so that has a big effect on MpKW, but it still does not explain the difference in regen. The route is the same each day. We are currently only using Drive and it is more fun. I may switch back to ECO and do another comparison once the temps become more consistent.

 

[Martir]

As stated above, regen is nice but not 100% effective.

A good rule of thumb is that you should never press any pedal unless you really have to. That might sound a bit stupid at first, but it's really not.

 

[Stoaty]

Ideally, you'd never use it at all, since you are not recapturing 100% of the energy. I.e, coasting is more efficient than regenerative braking, which is more efficient than friction braking....

There is one exception to this rule: if you are going down a very long, steep grade (e.g., 5 miles) you will do better using regen than just coasting. If you use regen, you get some of the energy back. If you just coast, your speed increases and the energy is lost to increasing drag. Confirmed on the downhill section of the southbound 405 through Sepulveda pass. In practice the difference is fairly small for this particular test. I am sure that abasile will report that regen is a very important source of energy for the battery coming down 5,000 feet from the mountains.

 

[mkjayakumar]

Perhaps this has been answered already, but maybe not.

Now that I have been driving this for a few weeks now, I have a clear understanding of how much range I would be getting in ECO mode On or Off and with AC On or Off. For my needs, I don't need the extra range one would get in the ECO mode, which I believe is no more than 5 miles on a full charge, or the having the AC Off which would get me another 7 or 8 miles. Given that, this is my question:

- is there any advantage for anyone to drive in the ECO mode all the time, besides the nominal higher range due to extra regen ? If I don't care for that extra range, what is the negative impact in driving in non-ECO mode ? more wear & tear of the brakes ? battery ?

-Jay

 

[lpickup]

I suspect you're not, but the way you're talking it sounds like you are putting a lot of faith in the +/- miles on the GOM when you switch in/out of ECO and turn the HVAC on and off. Just like the GOM itself, those are just estimates, and in my opinion not very good ones at that.

As for ECO, I'm actually starting to come around to the hyper-milers' way of thinking that says you want as little regen as possible normally and you should instead just coast (in N) or at the very least coast along "more" in D. Reason being that while regen does give you back some power, it's not as much as you put in in the first place. So the argument goes, ideally you should never touch the brakes or regen or anything for maximum range. That would speak AGAINST using ECO as every time you let your foot off the accelerator you are slowing the car down "unnecessarily".

But that's certainly not how I drive in real life. The way I drive I have to slow down all the time. So I figure that I might as well get something back when I do. So I use ECO mode 100% of the time. With my driving style, I am probably getting more range because of it (maybe it matches what the GOM states, but I doubt it). With a hyper-miling driving style you are probably getting LESS range because of using it.

Other reasons I use ECO:

1) As you stated, less wear on the brakes since I don't have to press the brake pedal as much.
2) I like the additional precision on the accelerator. Once you get used to it, I've got finer granularity on the low end, and full power on the high end when I floor it when I need it. In fact when I drive a gas vehicle now I hate how "sensitive" the gas pedal feels.

 

[Nubo]

...
Other reasons I use ECO:

2) I like the additional precision on the accelerator. Once you get used to it, I've got finer granularity on the low end, and full power on the high end when I floor it when I need it. In fact when I drive a gas vehicle now I hate how "sensitive" the gas pedal feels.

+1. It's much easier for me to keep the speed from "dancing around" with Eco. I think it also helps to foster a more gentle approach to acceleration. Even though I still have 90kW on tap when I want to enlighten someone who's moved into the alternate lane at a light because they don't want to be "stuck" behind a slowpoke electric car.

I also find I like the speed control that the higher regen rate brings when slowing. This is contrary to what I thought before I had the car, when I speculated that I'd just want pure coasting and regen only with brake application. In practical use with traffic there are plenty of times when you need to modulate your speed by a few miles per hour but more rapid deceleration than pure coasting will allow. The regen helps keep up with that with as little fuss as possible.

 

[ebill3]

When I first got the car, I figured I'd use ECO when I want range, and D when I want performance.
Hogwash - doesn't work that way.
I'm almost pure ECO now, - maybe some neutral coasting.

 

[dgpcolorado]

I use Eco most of the time because it makes it easier for me to be an "easy-does-it" driver and to keep my speed where I want it. But I routinely switch between Eco and D to calibrate my speed when descending hills, with changing grades and curves, without having to use the brake pedal. It's sort of a game to find just the right place to make the switch to keep my speed where I want it.

I find that trying to hold a "neutral" position on the A pedal to coast is almost impossible. For that I switch to neutral, but there are very few places where it is useful or safe where I live.