B gear?

READ YOUR MANUAL....
There is NO one pedal operation in a Prius. It's the same as the 2018 Prime that you had. It's used to slow the car on long downhill decent, just like any other car. Guessing on how a car operates, places yourself and everyone around you in danger.

Sorry for the rant....

 

Of course there is some controversy about this, but the B gear is meant as an engine brake. This was deemed necessary, because the Prius engine does not create engine drag when it's not engaged. On newer models the engine does engage, but the B function is still available.

Although rare, there could be a situation where regenerative braking is not available because the hybrid battery is at full charge. This results in the car picking up more and more speed on a long descent, to the point of danger, not unlike an 18 wheeler with brakes burned out, unable to slow down. It happens. I assume that Toyota didn't want to be responsible for such an incident with a Prius, so the B engine brake was provided.

I have tested this myself, and when the hybrid battery is fully charged, there is no regenerative braking. The result is that the car picks up excessive speed on the downslope. Friction brakes are sometimes not enough, and using them can result in excessive wear, and even brake loss.

The energy of the moving car must be dissipated somehow, and since regeneration and friction may not be available, the B position, engine braking is there to dissipate energy as heat by manipulating valve timing to achieve some amount of engine braking.

Of course some will disagree, but that's what my research and experience tells me.

 

even the bz4x doesn't have opd, unless they've added it since i looked.
ignore b gear, it'll go away eventually

 

try it when descending the grapevine...

 

In the MID there is a setting where you can change the level of regen between 1-3. I think level 3 is more than enough to achieve a one pedal type mode. If you need more than what the regen can provide you just add it in with the brake pedal. It'll slow you down to around 5 or 6 mph then you need to use the brake pedal to bring you to a stop. And like Paul G said a full battery won't provide much regen so plan accordingly.

 

And that's how it is 99% of the time, but you know how companies are about potential liability.

 

BAD ADVICE; If you want to drive a Tesla, drive a Tesla - because I don't want you to rear-end me!!

 

You can still use the brakes while in B mode. You're just engaging a more aggressive regen when you lift off the accelerator when you use B mode. So in B mode, if you don't need heavy braking, you can slow down just by lifting off the gas pedal. And if you need more than what regen is providing add in some brake pedal to achieve the amount of braking you need.

 

Even braking in D the car is using regen to do slow the car. You can see that on the power meter in the MID.

 

The OP used to drive a Tesla and apparently in one pedal mode.
Different cars, different operating principals - NO one-pedal operations in a Prius!!!!!
They're going to let go of the pedal and expect the car to STOP; We both KNOW the Prius WON'T STOP without applying the BRAKES!

That's the entire point of this thread; since the OP doesn't know how the car is suppose to operate, making them think it will operate like their old Tesla is dangerous at best.......

 

Perhaps calling it lift off regen above 6 mph mode is more appropriate then to avoid confusion.

 

Toyota programmed early and non-plugin Prius models so the deceleration behavior you feel in B is like a conventional car downshifted to a lower gear. You should notice that the car slows a bit more when you lift off the go pedal than it does in D. (Unlike a downshifted conventional car, B makes no difference when you're accelerating.)

Note that, just like a conventional car downshifted, this is not a "one-pedal drive" mode. While the car at cruising speed will slow more markedly in B when you lift your foot off, it will not come to a full stop, but end up moving forward at a creep speed like any other conventional car.

To make a full stop, you sooner or later have to use the brake.

Given that you have a 2025 Prius Plug-In, you are not limited to just one preprogrammed slowing effect in B mode: you can select Low (the default), Medium, or High, as described in your owners' manual under "Regeneration Boost". Here is that excerpt, uploaded to PriusChat a while back by someone else.

Even when you set it to Medium or High, it still won't be one-pedal drive. It will slow more markedly from speed when you lift off the pedal, but it won't come to a full stop unless you brake.

It successfully does what it's built to do, but one-pedal driving isn't what it's built to do.

In non-plugin Prius models (which have small battery capacity), it is built to let you take long steep downhills in a way that puts less stress on the battery. There's no other compelling reason to use it, in a non-plugin.

In plug-in/Prime models, which have a large battery capacity, you might use it in a wider range of circumstances, and try different settings of the regen level. But it won't give you one-pedal driving, and isn't likely to improve your MPG.


Technical details

The letter B should remind you of an engine-braking effect such as you'd feel by downshifting in a conventional car to slow down without use of the brakes. A Prius, though, has two ways of slowing down without use of the brakes: engine braking and regen into the battery. The car picks the combination it'll use to slow you down: driving in B doesn't mean it must use engine braking, and driving in D doesn't mean it can't use engine braking. Whether you're in D or B, the car has the same capabilities and will use them as appropriate.

The "Regeneration Boost" feature appearing in the gen 5 Primes/plug-ins can be seen as a sort of punning use of the same letter B.

Technical misconceptions

If you have been on PriusChat for a while, you may recognize the above from the many times Paul has posted it elsewhere. The bit about the engine not creating drag when it's not 'engaged' is a bit beside the point, because nothing in the Prius transmission ever disengages. The engine can be at 0 RPM whenever the car wants it to be, and of course it produces no drag then, but the car will also twirl it at up to 5,000 RPM, enough to dissipate around 11 kilowatts of power, and that also happens whenever the car wants it to. There's no extra step where anything has to 'engage' first. The car slows the counterrotation of MG1 and the engine RPM perfectly follows. This isn't something unique to newer models.

Frequent readers will also recognize this from Paul's previous posts. Paul seems to doubt that the car ever chooses engine braking on its own except when the driver has selected B. Some of the reason could be that Paul drives a Prime, whose much larger battery will rarely ever be charged enough on deceleration to trigger the car's use of engine braking in D. Two different times last summer, Paul set out to test the question, but neither time produced a result either way, simply because his battery didn't reach full-enough charge on either descent.

At some time later than those two attempts, Paul began writing that he has indeed run tests that confirmed his belief. (More at the link above.) But, if he is referring to any tests he conducted later after the two inconclusive ones, he's never offered any details of such later tests.

None of which is to say he wouldn't be welcome to post such results. We might learn something from finding explanations of him getting results that differ from what others get.

Paul has also repeatedly made this claim that the Prius gasoline engine uses valve timing manipulations to achieve engine braking—a confusion with the way Jacobs braking works on diesel-engine rigs.

On one occasion earlier this year, when advised of that confusion, Paul responded in an interesting way: by posting text from a Cummins Diesel page about Jacobs braking as if it had come from a Wikibooks page about the Prius instead.

Readers less familiar with Paul's posting history on this topic deserve to know at least that much about it (and can follow the links to see more if desired).

He tends to describe his position as simply questioning a 'consensus' among other PriusChat members about how B mode works. Which, ok, as long as one sees that what he calls the 'consensus' involves many other Prius owners who have tested the behavior themselves and often documented it, including with instruments and whose experience doesn't match what he claims.

 

Of course none of that is supported by evidence.