Driving in "B" Mode Regularly

Unfortunately, in B mode, you can’t activate cruise control.

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Regarding EV Auto:

I’ve never tried EV Auto yet, since I bought the car in May. In my view, it would have been much more interesting if it were defined as, more or less, “EV below 50MPH, and HV above.” That, rather than “fire up the engine for acceleration assistance.”

As I read it, over-simplifying a lot, HV mode uses the ICE for purposes: long, sustained power at medium-to-high speeds, and acceleration force when you trounce on the accelerator, and tries to use the MGs elsewhere. EV Auto seems to add the ICE for what I perceive as exactly the wrong one of those two uses: I’d prefer it kick in the ICE for long, sustained, high-speed power where it’s the most efficient, an never gunning up the engine in low gear, which is exactly where it’s the least efficient.

Regarding B Mode, this is one area where Tesla, BMW, GM, and Nissan are being *a whole lot* more innovative than Toyota:

I definitely do feel a little more regenerative braking in EV B mode than “D”rive mode, but it’s not as big a difference as I’d like.

Teslas work like EV B Mode, but with *a lot* more additional regeneration. The gen-2 LEAF has an “e-pedal” option that I gather is more or less patterned after BMW’s: Basically Tesla taken to an even greater extreme — it will not only just *slow down a lot* as you take your foot off the accelerator, but in fact will *take it to a complete stop* after it slows down enough. With a Tesla, you still finally have to hit the brake to get it to completely stop, but not with an e-pedal. I gather the e-pedal is superb for stop and go traffic! The Bolt and gen-2 Volt have a “regeneration paddle” on the back of the steering wheel, each press of which will progressively dial in more regeneration, until the car comes to a complete stop.

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Might work in EV mode, but is definitely bad in HV mode. (which I know you kind of said.) With the car fully warmed up, no charge in the EV porttion of the battery, I did two four mile loops, one in regular HV, one in HV in "B" gear. In regular mode I got 62 mpg. In B gear, I got 53 mpg.

 

Yes, I am seeing good results with regeneration in B mode in EV mode in driving around town. Thanks for suggesting it.

 

I've been experiencing with the transmission in the B position in the EV mode, and I haven't experienced any improvement in mpge whatsoever. In fact mpge is likely worse in the B position in the EV mode, as the car is jerky when you decelerate and you have less control over regenerative braking. Therefore, my verdict is that it is useless to drive in the B position in the EV mode—the car is harder to control and mpge seems inferior. I would only use the B mode when it's necessary, such as driving downhill.

However, for heavy-footed drivers, perhaps the B position improves mpge by making up for some poor brake-pedal use.

Tesla recently started one-pedal operation on Model 3, which, along with possibly some electric motor redesign, have resulted in a significant improvement in the EPA mpge, and Model 3 has now taken Prius Prime's crown for having the highest mpge. Perhaps the EPA test procedure is more sensitive than my driving style to the pedal operation as far as motor regenerative braking is concerned, or perhaps it is entirely because of the possibly new electric motor.

 

I was initially taken aback with the sudden deceleration and reverted to driving regularly. Then I again got serious and tried the B mode and liked that I could actually modulate the sudden deceleration using the accel pedal. I am able to take turns without going to the brake pedal and I have seen visible improvement with the EV range.

 

I have a 2011 Prius III, not Prime or C. I drive 95% of the time in B mode. I consider it one of the best features ever added to the driving experience. A single pedal controls both the gas and most of the braking. You need to drive in B for a day or two to re-educate yourself on how to drive a car. The de-acceleration of B mode is not just on or off. You regulate, or modulate the amount of de-acceleration or coasting with the "gas" pedal. You are not using gas, The gas engine does not come on during de-acceleration. You are telling the car how much you want the generator to slow you down. The amount is completely variable.
In town, you don't slow too soon. You learn to use the "gas" pedal to control your rate of de-acceleration. You re-educate yourself on how to drive the car.
On the highway, with mild or heavy traffic, you don't need to keep switching between the brake pedal and the gas pedal. One pedal does it all. Only in emergencies, quick stops or slow downs, or stop lights do you need to use the brakes. You are never braking too hard or too soft like when you jump off the gas pedal and switch to the brake pedal. One pedal does it all, and is completely variable.
Of course, the B mode is charging your battery more, giving you more energy to draw from. You are not wearing down your brakes either. You tend to use your brakes very little.
The only time I don't use the B mode is when I want to use the cruse control. Cruse control will not come on in B mode.
I also drive a lot of mountain roads. I love the variable braking you can do in the B mode. Again, you are not using gas when push on the "gas" pedal to lessen your braking amount. The gas engine does not come on. You are just telling the car to do less regenerative braking.
The only drawback I think of is your brake tail light is not going on as much as in D mode. B mode only slows you down. For quicker stopping and alert the driver behind you, you are going to use your brakes, and the tail lights come on.
I consider the B mode one of the best safety features added to cars in a long time, and it makes it so much easier to drive the car.

 

IIRC engine shut-off doesn’t happen with gear selector in B?

 

This thread was started some years ago when Prius Prime was still new and not many knew about the behavior of the car and the effect of having a larger traction battery capacity on the Prius Prime for pure EV mode drives. Since then, many have tried and did not see the initial observation the OP posted at the start of this thread.

The B shift is totally unusable for my normal routine driving. I almost never have "stop-and-go" type traffic to contend. The braking in general is a very rare event for my PP. Even though my overall average driving speed is around 30mph, my regular routine driving includes over 50mph instant speed on most of the trips I use my PP. And the worst part of using B shift is the propensity for the engine to start on the steep downhill while in EV mode. This can even happen with D shift if the battery is full, but with B shift it happens more often even when the battery is half empty.

I experimented with B shift for a while, but for my daily driving habit, it uses more gas and does not add EV range.

 

Doesn't the "transmission" stay in a lower gear all thru while you are in "B" gear in Hybrid mode?

 

There is no "transmission" or gears in a Prius! In B mode, when you lift off the accelerator, the motor generator(s) simple go into a more aggressive regen mode causing the extra "drag" you feel slowing the car down by converting your speed into energy that goes back into your big battery. Plus, cruise control will not engage and the ICE will not shut off in B mode.

 

The Prius e-CVT transaxle does have gears and a differential. There are no operating clutches, torque converters or even hydraulic pressure in the transaxle. One solenoid engages the park pawl. The planetary gears are always engaged and do not mechanically shift. The motor generators are part of the planetary gear drive as is the gas engine and the wheels. Changing the rpm, torque and direction of the electric motors changes the overall gear ratio and drive direction under computer control.

B mode does use a lower gear ratio to provide unfueled engine braking for long mountain descents. Using it wastes energy as heat and is for safety on those rare occasions when long mountain downhill regen fills up the hv battery and friction brakes might overheat from excessive use. B mode is inefficient on normal roads and will hurt mpg.

 

^^^ that, mostly, except that the parking pawl isn't moved by a solenoid. It's moved by an electric motor that spins a trochoid gear reducer giving a 60:1 torque multiplication, which it might need, for example, to pull the pawl out while the car is resting against it on a hill. A solenoid that could do that would be kind of monstrous.

 

Jeff may be gone? Hopefully read the comments.

 

The Prime uses more regen in B, assuming the battery isn't near full charge. Otherwise, B engages engine braking.

 

When I am de-accelerating in B mode the gas engine always shuts off. When I am going at a constant speed or accelerating, the gas engine, if needed, will come on.
When driving at a constant speed or accelerating in B, you are not working against the generator barking. Generator braking is only applied during de-acceleration.

 

The behavior may be different between regular Prius and Prius Prime. This thread is about Prius Prime and using B shift while driving in EV mode without engine help. The experience I have had on my PP with B shift while driving on EV mode with enough battery % left is that in any downhill there is more propensity for the engine to turn on. This also happens in the D shift if the battery if full and the downhill is long enough. But B shift makes it more susceptible for the engine to start up when we don't want or don't need the engine to come on.