Downhill driving strategy

Safety and law aside, the energy conversion loss should be greater than the higher speed drag loss.

If it is a lower traffic area, the most efficient and safest would be to allow speed to slip before the crest of the hill, such that it ramps up just to the desired upper limit on the downhill. This is practical only on short hills, not long ones where you approach a terminal velocity.

Oh, you live in California? Nevermind, the needed 'lower traffic' doesn't exist there.

 

I wonder where car puts energy from electric Motors since they are disconnected at N-position.
Personally i dont use neutral ever, only in required places for example some carwash, but those ones i avoid also.

You can put car to "neural" also with gas pedal by pressing it so litte that power needle is at the line what is between charge and eco meters.
Also doing that way, car can handle its electronics as it needs.

Also for long downhills, pressing brake for regen is not so good idea, after battery is full then regular brakes are used.
If you use Cruise control, it can handle situation by itself. It uses neural energy position to maintain constant speed and if downhill is long, then it will regen and after battery is full it uses B-mode automaticly.

 

I'd go with that.

 

What energy? When disconnected in Neutral, the motor-generators are de-energized. They don't produce any energy to be put anywhere.

 

Though it's not exactly your question, if you decide not to simply coast up and down, but instead to apply the brake when going downhill and accel when going back uphill, let me suggest putting the Prime in "B" instead of "D" while going down the hill, especially if you're in EV mode. Again, this is not a comment on whether to do coast vs brake & accel, but a suggestion that if you do decide to do brake & accel, to put it in B instead of brake when going down the hill.

(Side note: when in HV mode, I use B only when going down a big hill, otherwise it's not as efficient. However in EV mode, I put it in B all the time, and have been for over a year now, even if driving flat, as there's no loss of efficiency like there is in HV mode if driving in B, as long as I remember to put it back to D as soon as the EV range runs out. If I'm driving flat in EV MODE, B doesn't help or hurt either way as opposed to D, but if I'm doing hilly driving, city driving or start-and-stop, I find "B" extends the EV range and is the way I like it once you get used to it, more like 1-pedal driving, so I just keep it in B all the time as long as I'm in EV MODE, but this is a personal decision). Anyway, as for your question, if you do decide to go the "brake & accel" route instead of the "coast only" route, instead of the brake, try putting the car in B when going downhill...

 

It was my understanding that if you put the car in neutral, it will not charge the battery when coasting. If you are going downhill you can also put it in "B" which will keep the speed down, kind of like down shifting and charge the battery. Or you can gently apply the brake to keep the speed slower and charge the battery.

 

Law section.
Should discourage you from N.

Several choices your computers may wish to implement are disabled in N, it can't start the engine, stop the engine, charge the battery , or use the engine as an engine brake. So all you have are friction brakes and a draining battery. I recommend N in extremely rare situations, cleaning the brake rotors of surface rust is one. I can't think of two.

 

That is why OP expects to be drifting up to higher speed. The battery charging drag is removed.

For the purposes of OP's question about efficiency, EV-B mode should be approximately equivalent to the light braking he was using, despite the different footwork.

At least the Prime provides this choice. At these speeds, our regular non-plugin liftbacks have only an HV-B mode, which is not equivalent.

 

driving with the car in N is just a bad idea. even going downhill you never know when an emergency might arise that you may need to add some energy to get out of. If you're in N that may cost you your life. As gettyz said, just push slightly on the gas to put the car into a neutral energy state (neither using or generating electricity... the old "glide" mode of the pulse and glide strategy.

 

EV-B mode "turns up" the regeneration, like lightly pressing the brake pedal, which is fine until the battery is full. As I recall, HV-B mode is engine braking. Sort of like compression braking for diesels, but instead is really vacuum braking in the Prius. It slows you down without applying the friction brakes, but is still just throwing away the energy.

 

It's only "throwing away" energy if your EV battery is 100% full, otherwise the energy goes to recharge the battery. And if you're driving in EV mode (as I mentioned, use it constantly only in EV mode, for HV mode it's only for going down a hill or grade) the battery very quickly won't be empty anymore...

 

I cannot speak with certainty, but my understanding was that if you are in HV mode and set B mode, that engine braking kicks in to slow you down, rather than regeneration. Maybe there are other conditions (batttery state of charge, speed, whatever) that come into play here. There were long extended discussions about this a couple of years ago for the first generation plug-in Prius, and I really don't recall how it all sorted out, or how it may be different for the Prime.

 

I have tried EV and B in city driving and cannot notice any more regeneration than EV and D with braking as long as the braking is light. I am biased for using D because I like using cruise control, even in city driving. It helps keep me at the speed limit, but does need to be turned on and off a lot, either using the stalk or the brake.

 

I've only had my Prime for a week so I can't speak for how it works yet for driving on hills. But when driving my 2006 Prius on the highway where there are bigger hills, I always thought it was more efficient to accelerate while going downhill to build up speed without using much gas. That way it wouldn't take as much gas to go up the next hill because you have more momentum when you start going uphill. Just have to make sure that along with paying attention to your speed that you're also paying attention to the traffic around you to make sure that you don't run up someone's butt on the way down or slow traffic behind you on the way up. And also make sure that there aren't any police/highway patrol when you're accelerating downhill.