'B' Mode revs engine way up, normal?

Regen can and does provide a quite dramatic brake force in 99.9% of US driving with controlled grades. But if you truly fill the normally 80% battery to 100% using regrn then old fashioned engine braking occurs, initiated by continued brake pedal operation. This will rev up the engine, turn off fuel - just like manual downshifting in older cars. If needed friction braking is automatically added. Normally friction braking is only needed below 10 mph and brake pads can last 280000 miles or longer such as in my case.

B mode maximizes regen immediately and will fill the battery quicker without having to press the brake. The system will still shift to engine braking when the battery is full. In reality B mode is not needed and I personally never use it even though I live in serious hill country on a steeper than normal private road.

Regen braking does not rev the engine as long as the battery can accept charge. Which becomes an operational advantage EVs and Primes have over regular hybrids, eg much longer regen mode braking due to higher cspacity batteries.

 

Once the battery is full (around 80%) it essentially wastes the energy by using the engine configured to provide high resistance, hence the high revving that people notice.

 

This is not correct. The purpose of B mode is to increase the time taken to reach 80% so electricity generation is reduced with the difference made up by adding engine braking to give the total braking force requested.

 

* I don't recall B-mode engine braking ever exceeding the maximum regenerative braking into the battery. They feel about the same;

* The non-plug-in Prius maximum battery power is what? 26 or 27 kW? Therefore, apart from some electrical conversion losses, regenerative braking also does not exceed this power;

* ChapmanF's post yesterday, pointing back to his previous experiments, suggests a maximum engine braking power of around 14kW;

* The mechanical power of braking is a proportional to vehicle speed, and to mass (or weight, for Earthlings);

* Watching the HSI display charge bar while braking, I find that it "pegs left" fairly easily under what I would call light to moderate braking, depending on speed. We have been told here that regenerative braking is at most the un-pegged portion of this display. Once pegged, all additional braking is necessarily friction braking only;

* Very many people, including my spouse, very regularly and habitually brake into the HSI "pegged" zone, with what I was still characterize as moderate braking, not "braking really hard";

* At highway speed, full power panic braking (friction) in a Prius can exceed 500 kW, far far far above the maximum regenerative- and engine-braking powers expressed above;

* All this leaves a very large gap between the maximum possible engine braking power, and what I would describe as the "braking really hard" where several members here claim that friction braking even starts. What kind of braking is being used in this gap? I'm believing that it must be the friction pads, until others can show otherwise.

"Quite dramatic brake force"? Yes, it contributes a lot, and with a bit of training, a Prius driver can place most of their planned, non-emergency braking into this regen zone. But it isn't automatic or intuitive to many non-technical drivers, and it doesn't come anywhere close to providing 99.9% of even everyday braking.

My household -- even my harder-braking spouse -- averages about 100k miles on the factory pads of our stick-shift vehicles. If regen replaces 99.9% of that, then the Prius pads should last 100 million miles. Right? Nobody should ever wear out their Prius pads, even those who need pad replacement by 30k in a regular car.

I'd suggest that pad replacement at 280k means that regen displaced a bit less than 2/3rds of regular braking. Vastly short of 99.9%.

That does not describe my Prius. In mine, B-modes splits the 'regen', sending part into battery charging, and part into engine braking. Engine RPM immediately steps up part way, then takes an additional step up when the battery approaches full. Maximizing regen into the battery requires either the brake pedal, or cruise control. I use B mode only for the longer descents where the battery cannot take all the possible regen braking.