Not liking one pedal driving

[ajdelange]

Where is this efficiency graph you guys are talking about? My Ford Fusion had one. You say it does not work well for this. I don't think that I have seen it at all.

It's there but it won't help you monitor regen because it displays the reciprocal of the consumption rather than the consumption. When you slow with regen the consumption goes from positive to negative which means it has to go through 0. The reciprocal thus goes from +∞ to -∞. There are no negative numbers on Rivian's display and the + side scale is extremely compressed so that the display saturates at low consumption and you can't see a transition from no regen to regen. I have asked what is displayed as a driver goes in and out of regen but never gotten an answer, The power meter should show it though (I assume there is a power meter).

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[fallen888]

The OPD will really throw you forward in your seat if you let all the way up while doing 25 mph or so.

You gotta feather the accelerator. As many have said, you don't just let go of it completely - that's not how OPD works.

Everyone has nailed it with their comments. You can’t simply pull your foot of the accelerator pedal and you must simply learn to adjust your pressure on the pedal to slow down.

100% After dog knows how many years of traditional driving, you just have to reprogram your brain for OPD and it'll take a little time (varies by brain). But once you get it, you'll never look back.

 

[SoCal Rob]

While I have my own concerns over OPD, I doubt that Rivian will permit a setting to completely eliminate regen. I think the issue is range and perceptions. If you have a driver new to EVs who had the ability to turn off regen then it will probably negatively impact range. You could have people claiming that Rivians don’t go as far as stated which is a much worse look for an EV company compared to people admitting they are having a hard time adapting to a newer way of doing things.

I think adaptive cruise control will eliminate most issues that most people have with OPD, including the ability to cover the brake.

 

[ajdelange]

If you have a driver new to EVs who had the ability to turn off regen then it will probably negatively impact range.

It absolutely will. That is what it is for. As you drive it is necessary at some times to speed up and at others to slow down. The latter requires drawing kinetic or potential energy from the roadbed nd that energy must be disposed of. We have a choice of converting it to heat (friction brake) or back to electricity which is (for the most part) put back into the battery (regen). With the friction brake the energy is forever lost to us. With regen we have recovered most (but not all) of it. The regen improves range (and saves on friction break system component wear).

When driving ICE the mantra for best range is "Keep your feet off the pedals." With a regen equipped BEV it's "Don't use the pedal to accelerate or decelerate". Were regen 100% efficient we would have such a caveat but it isn't. In either case we add "If you must, make a control input amke it smooth". Follow those rules and it shouldn't matter the mechanism by which your thrust commands (positive or negative) are communicated from you to the vehicle.

A driver that gets hurled into his seat belt when using regen isn't using it right. He probably gets thrown around driving ICE or his BEV with regen off. My wife cannot follow these rules. You are going to get tossed around whether she is using regen or a friction brake. The problem isn't with the regen - it's in the fact that she either doesn't have the Kalman filter most of us do or it isn't tuned properly. Properly drivenit is an easy matter to make every stop a chauffer's stop, regen or not.

Option to turn it off? I think most manufacturers offer that. Some people just don't like regen just as some don't like the metric system. De gustibus non est disputandem!

 

[SoCal Rob]

It absolutely will.

Not quite.

A true statement is that regen will meaningfully improve range in the overwhelming majority of real-world driving situations. It is not an absolute, however.

 

[ajdelange]

Not quite.

A true statement is that regen will meaningfully improve range in the overwhelming majority of real-world driving situations. It is not an absolute, however.

I'm sitting here trying to think of a scenario in which choosing regen would NOT increase range. Obviously you have one or more in mind. Would you share it (them)?

 

[blturner]

It's there but it won't help you monitor regen because it displays the reciprocal of the consumption rather than the consumption. When you slow with regen the consumption goes from positive to negative which means it has to go through 0. The reciprocal thus goes from +∞ to -∞. There are no negative numbers on Rivian's display and the + side scale is extremely compressed so that the display saturates at low consumption and you can't see a transition from no regen to regen. I have asked what is displayed as a driver goes in and out of regen but never gotten an answer, The power meter should show it though (I assume there is a power meter).

I found the power bar that has been mentioned. It is so small I would need my reading glasses on to see what it has to say. And yes it seems to respond way too slowly for learning regen feel.

 

[ajdelange]

I found the power bar that has been mentioned. It is so small I would need my reading glasses on to see what it has to say. And yes it seems to respond way too slowly for learning regen feel.

They definitely need to do some work in the energy monitoring department. I guess I have no objection to the current "dumbed down" approach but I think they need to offer an "advanced" display option for those of us who are interested in what our vehicles are really doing.

 

[ajdelange]

I'm sitting here trying to think of a scenario in which choosing regen would NOT increase range. Obviously you have one or more in mind. Would you share it (them)?

I did think of one and that would be one in which the driver vows to never decelerate by any means other than drag, rolling resistance or gravity in other words he will not touch the brake pedal whether regen is on or off. As regen inceases range by recovering energy otherwise wasted in the brake then clearly a scenario in which the brake is never used does not benefit from it. But in the real world....

 

[Gshenderson]

After a couple of days driving the Rivian, I will say that it feels to me like the truck needs a little too much pressure on the Go peddle to transition from fully stopped to moving - thus making those transitions feel jerky. Hopefully it’s me and not the truck, and I will get better at doing smoother transitions over time. My Tesla was just naturally smoother than the R1T seems to be.

 

[SoCal Rob]

I'm sitting here trying to think of a scenario in which choosing regen would NOT increase range. Obviously you have one or more in mind. Would you share it (them)?

Given that regen works by capturing as much energy as possible which would otherwise be lost to friction brakes, the less slowing you do with friction brakes, the less of an advantage regen gives you. I seem to recall that this is part of the reason why hybrids typically get better fuel economy in stop and go driving than they do at steady highway speeds, with wind resistance being the other factor.

An example where regen will not increase range: two identical EVs (one with regen on and one with regen off) start at the top of a mountain with fully charged batteries. They are able to drive continuously downhill without ever using any power to accelerate. At the end of their journey the vehicle with regen on has the same range as the one with regen off.

I can think of other scenarios where regen may not help meaningfully, but most of them are not real-world driving situations. That’s why I agree with qualifications (meaningful & real-world) but I couldn’t say it was an absolute and feel honest.

 

[SoCal Rob]

I did think of one and that would be one in which the driver vows to never decelerate by any means other than drag, rolling resistance or gravity in other words he will not touch the brake pedal whether regen is on or off. As regen inceases range by recovering energy otherwise wasted in the brake then clearly a scenario in which the brake is never used does not benefit from it. But in the real world....

I posted my reply after this and agree, it’s about the real world but it’s not an absolute.

if you want a ridiculous scenario I think there is even a way to arrange a test such that regen would reduce range.

 

[MichaelD]

start at the top of a mountain with fully charged batteries

I'm being pedantic, but you won't get any regen from either vehicle in that scenario -- the power would have no place to go you need to consume some charge before you get regen back, so it's friction-only until then. This is from experience with various Tesla models -- cars with built-in battery buffers may vary in how they behave.

edit: I guess maybe that was your point?

 

[ajdelange]

I'm being pedantic, but you won't get any regen from either vehicle in that scenario

I don't think you are being pedantic. In any scenario one is likely to encounter regen is going to be beneficial in terms of range. One can construct scenarios such as the hill one or we can say that the battery is very cold to the extent that the car turns off regen so that is no benefit in selecting it because the car won't allow it. IOW you are in that academic arena already.

Change his gedanken experiment to start at the top of the hill with 70% SoC. Now whether there is any benefit from regen depends on whether the drivers use vehicle braking. If m*g*sin(alpha) is greater than, equal to or less than the sum of drag and rolling resistance. Let's assume that a couple of guys pusg the vehicle over the edge of the hill to get it started. If m*g*sin(alpha) is less than the sum of the retarding forces the trucks will slow and stop. If the friction brakes werent touched there would be no benefit from regen. Were m*g*sin(alpha) equal to the sum of the retarding forces the two vehicles would roll down the hill at the starting speed, come to the bottom and continue along the level to eventually stop. If the friction brake is never touched there is no advantage to the regen truck. If m*g*sin(alpha) is greater than the retarding orces the trucks will accelerate down the hill, reach the bottom at perhaps considerable speed and proceed out onto the flat where eventually they will be slowed to a stop by drag and rolling resistance. If no one touches the friction brake or used regen then there is no advantage but if one driver slows with regen (as he is likely to do if the hill is long and steep) and the other the friction brake there is an advantage to the regen car because he has recovered the potential energy of his truck at the top of the hill. In these cases one either dissipates the potential energy entirely in frictional forces (drag, rolling resistance, friction brake) or recovers a good part of it in the battery..

This kind of excercise always reminds me of the dump truck in service at a quarry somewhere in Europe that is never charged. It's job is to deliver rocks from the quarry which is high up on a mountain side to a processing plant in the valley. The regen energy recovered when going downhill with a load is apppreciably less than the energy required to return the empty truck back up to the quarry,

 

[SoCal Rob]

I'm being pedantic, but you won't get any regen from either vehicle in that scenario -- the power would have no place to go you need to consume some charge before you get regen back, so it's friction-only until then. This is from experience with various Tesla models -- cars with built-in battery buffers may vary in how they behave.

edit: I guess maybe that was your point?

Yes, that was my point. Turning off regen will typically (almost always) reduce range but to say that, “It absolutely will.” isn’t accurate.

Maybe I was being pedantic, but my point is that when people use absolutes they can undermine credibility in the eyes of their audience if the reader can think of one or more exceptions.

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