Initially I wasn't sure what 'B' position in the shifter. After googling (who will read manuals these days ) I came to know that it is for negotiating the steep downgrade so that brake doesn't heat up. I was wondering if B mode can be used while slowing down during normal driving condition, so that the energy is used for charging the battery rather than using up the brake pads. I am quite amazed by the whole synergy drive tech. I also kind of little puzzled by the logic used for showing EV miles. If it gets depleted completely (zero), then it will never go up no matter how long you drive. However, if there is something left in the EV miles, and you switch to HV mode, it can go up during your regular driving.
If you're in EV, engaging B will just increase the amount of regen, which will slow your car down more than just coasting (foot off the accelerator). If you engage B when your battery is near full, then it will turn on your engine. So just be aware of that. If you are in HV, then it will slow you down, but it will use engine braking. There have been many reports of people running out of EV range but being able to regen enough energy to be able to get back into EV. It just takes a longer downhill section of road/highway. Someone will probably chime in here, but if I recall, you need to regen back into the 28% SOC range before you'll get any EV miles back, IIRC.
If you engage the B gear below 20 mph (guesstimation), it'll brake by recharging the battery. If you do that at higher speed, the gas engine will be spun and act like an air pump (wasting energy) while charging battery.
So when dealing with a speed limit (i.e. 30mph downhill), is using B (when battery isn't full) downhill as good as cruise control set (which seems improve regeneration compared against coasting down) when it comes to recharging the battery?
I'm not sure, but I think that if you have exhausted your EV range and are locked into HV mode, that going down a hill with B will engage (wasteful) engine braking, but using cruise control will use extra regeneration, just as would lightly pressing the brake pedal. It is not clear to me exactly WHY they would use engine braking for B in HV mode instead of regeneration if the battery is not full, but that is what some posters have reported.
Cruise control down hill is just like lifting all the way off the pedal. So, if that is not slowing you down enough you should keep it in EV and press the brake staying in the "regen" section. If that still is not enough you can use B to slow you down more and not use the friction brakes. And yes you can regen quite a bit of EV in the PiP. Here I got back about 4 miles.
I don't know if it is just the DRCC in the Advanced, but I know that it very aggressively uses regeneration if it detects that I am closing in rapidly on a vehicle in front of me. A lot more than just taking one's foot off the pedal, and it isn't using engine braking or the friction brakes. But it is my understanding that cruise control even on the standard Prius will use regeneration to slow you down to the set speed, until the battery is full.
I will do some more testing with CC. I didn't not see it regning as much as with the brakes. I have a base so don't know how the Adv. works.
Because your brakes are regen to a certain point, I would stick to gently pushing the brake. B is probably not worth it.
Thanks for all the info, I found this article which was pretty useful. Looks like the magic number is 7 mph. If it goes below 7 mph, there is no regen. Check the section "Braking and deceleration" in this link Better Gas Mileage in a Toyota Prius | Hybrid Cars
normal braking will first start with regen and only switch to brake pads when that is deemed insufficient. plenty of regen happens in D mode. personally, I've never used B in all the years of Prius driving.
is it correct to assume in B mode once the regen bar on the HSI (left side) is full, the engine braking will kick in thereby costing charge?
Yes, the battery can only take so much charge at a time. You are getting 100% charge but are losing excess potential energy to heat via brakes or ICE pumping force. So, brake earlier and over a longer time to maximize charge. But there are times where that is not enough, so you either use brake pads or use "B" ICE pumping force to help.
as far as I can tell, when you are in EV mode, no engine braking kicks in – only regen. that's why i said that it's counterintuitive for those coming from the liftback.
