Pressed pedal, engine revs but no power to the wheels...

Never use B mode short of an emergency. Braking mode is there for regulatory compliance. You're not driving a truck. Your brakes will last the life of the car (unless you live in Buffalo NY then they'll rust out).

 

B Mode is convenient when you are descending a long grade and don't want to sit on the brake pedal. We have several roads near me (Oakland, CA) where it is a convenient option to have.

 

I would reserve B for extremely long downgrades, only use it where the car may refuse to charge further, dump the braking task 100% onto the friction brakes, well before the bottom. That would be at least a mile of sustained downgrade.

 

B mode is great for stop and go driving, provides a bit more drag so you don't have to hit the brakes as hard or as often. Also, IF you have a Plug-In model, going downhill, when the battery bars fill up, it will just switch the battery gauge to solid and charge as if you were plugged in. The most I've ever got on a hill was 1.0 miles of charge


iPhone ?

 

On a regular Prius, it'll also ensure less charging. Seriously, relegate B mode to mountain descents.