Best strategy for a long cruise down hill

The system is more intelligent than that and will not "overcharge" the battery as you say. That energy just isn't captured and goes to waste. It's a lot like your phone, the circuitry knows when the battery is full and stops charging it, even if it remains plugged in. It doesn't keep charging the phone until it catches fire.

You could use B (engine braking) if you wanted but it doesn't sound like your drive requires that normally. Using B will allow you to drive more relaxed since as soon as you take your foot off the gas it will start braking for you. There's a section on this in the manual.

By and large, the whole car is designed so you don't have to change the way you drive to get good gas mileage, but if you do you can really do very well.

 

As GV mentioned, the car's charging system is smarter than that, and for protection, quits charging the battery. Otherwise, the provided battery warranty would be impossible.

B mode uses engine braking, not the mechanical brakes. Try it, but don't necessarily take your foot off the gas pedal. Instead, apply just enough 'gas' to get the ground speed you want, i.e. use just a portion of the available B-mode drag. It isn't an all-or-nothing thing, you can control the amount, and also control the engine RPM so that it doesn't spin to banshee-screaming level. This will delay filling up the battery.

(Of course, the engine isn't really burning any 'gas' in this mode when it is doing engine braking.)

 

On my Gen3, there is a rounding issue on the battery SOC display. E.g. 7.5 internal bars rounds up to 8 displayed bars, somewhat before the limit is actually reached, so I see so regen still happening for a bit longer after the battery displays as full. But it will stop.

I don't use the Gen3 energy flow screen because it is much less useful than Gen2 version. Gen3 shows the arrow flows even when the amount is negligible but non-zero, making it impossible to balance out to no arrows at some speeds when gliding. The Gen2 version will blank the arrows when 'close enough'. For Gen3, the HSI screen is much more useful. I don't have any experience with Gen4 displays.

If the slope is shallow enough, D mode engine braking will be sufficient, and far more quiet than the full-on B mode engine braking.

 

There has been a lot of discussion on this over the last 2½ years.

I sense that Gen 4 actually goes into a form of "B" when the battery is full - as others have suggested, B seems not so necessary until: 1) the battery is full to the last (rarely used) bar; or 2) it it's a quite steep hill, I still have used B at that stage, and I had to use the brake pedal less.

 

I have observed my Gen 4 using engine braking on its own when decelerating down hills with a full battery. My guess is B is only required when the "auto B" isn't enough to control acceleration and you don't want the friction brakes overheating.

 

7 downhill miles is quite a stretch; I would experiment with B mode. I use it (with a 3rd gen) coming down our Mount Seymour (ski hill), that's about it. In stretches that are steep enough that I'm braking, I'll shift to B. Where it flattens out enough that I need to give gas, I'll switch back to D. Mostly I stay in B, all the way down. I keep the speed down too: the engine sounds more "alarming", the faster you go.

The battery displays full by half-way down, but it appears to continue doing some charging all the way down; I've never noticed a precipitous shift over to friction brakes only, at least it's not apparent.

Anyway to skirt it? I'm guessing no, but just a thought.

 

No. Wrong.

The "system" will take care of itself nicely.
So will the cruise control, at least in my experience.

Set your cruise for a safe speed . Hopefully the brakes won't be needed as that cancels the cruise and complicates matters.
When "engine braking" kicks in there will be a lot of noise; perfectly OK.

Manually switching to B mode isn't necessary because the cruise control will invoke it automatically.
But use it if it makes you feel better somehow. It certainly won't hurt anything.

 

If you want to let the car use all its smarts, just set the cruise control to maintain the speed on the way down

 

As do prior generations.

B and D use the same tools to limit speed downhill, but with different combinations and limits. D mode uses just mild regeneration until the battery fills, then switches over to mild engine braking. B modes uses regen and moderate engine braking simultaneously, then moves to hard screaming-banshee engine braking once the battery fills.

Tests on my Gen3 found that D mode engine braking is limited to about 2000 RPM, fine for shallow descents but not anywhere near strong enough on some of the steeper hills. B mode will push up into the 2500-ish RPM range before the battery fills, then can climb up as high as 4600 RPM after the battery cuts out.

On some of my highway descents, even B isn't strong enough, so I must manually add some friction braking, though vastly less than if B wasn't used.

 

There is a way to skirt this mountain, isn't there: you're just not letting on...

Seriously, if there's two routes, and one avoids the climb/descent, I'd go for it. Daily hill climbs/descent do take a toll on the battery, and the engine; there's no free lunch.

Same here, on my nemesis (Mount Seymour): B mode and braking, most of the time. I find when you use the brakes (in B mode) it sounds like revs go up more so (hey, if the car had a tach...); I'd speculate the computers detect that you're using the brakes, increase the engine braking correspondingly.

 

If you are using adaptive cruise control the system will use as much engine braking as necessary to control the speed.

While recently traveling south on I5 from Oregon to California where there are long hills that drop a a few thousand feet the car I saw up to 4,700RPM used for engine braking while in 'D' with adaptive cruise control.

The car did not go above my set speed (60-75mph) on any of the hills, even without me using the brakes or changing to B (which would disengage cruise control), I couldn't tell whether it also automatically used friction braking on the steeper sections.

It worked very well and I didn't have to use accelerator or brakes for very long periods except when traffic or road conditions forced me.

It may not be as aggressive when not in cruise control.

kevin

 

I don't have an adaptive version of cruise control, but presume that it is still strictly traffic-adaptive, not curve-adaptive. So I'd often end up tripping it out and needing to re-engage it frequently.

 

Yes, as long as you've got a car in front, that works well (as long as you're happy with the speed they're driving).

 

I just drive it.

In my mind, the Prius is no different than any other car I drove. When going down a long hill I take my foot off the gas.... and press the brake pedal occasionally and the car starts to slow down.

Give me some good old fashion "friction brakes" any day! That fancy "regenerative" stuff never slowed me down... it just recharges the battery.

 

I was talking about your particular drive, where you said in your original post that you used to drive your CR-V comfortably barely touching the brakes. You were asking how to drive the Prius down the same route and I gave my answer.