What I don't like about the 2016 Prius

And I like this feature. I consider it a speed hold feature. The car is trying to keep me at the speed I set the cruise to. BTW... it is still regenerating while using the engine to slow down the vehicle.

 

No.... it doesn't inhibit the car from accelerating any more than if the engine were off. No pedals means slight regen. When the engine is on, that energy (or at least not as much energy) does not go into the battery.
There is no reason for the engine to be on if the battery is not full and the battery is not overheated or too cold. Thus the cruise control algorithm is stupid. There is no advantage. ?????

 

Other than ensuring that there's regen capability in reserve, because it doesn't know how steep the hill is.

 

I have evidence to the contrary every day on my commute. If you are on a steep enough slope with cruise set and the regular regen can't hold the car to speed the engine will engage for engine braking to keep the car at the set speed.

When using the engine braking to slow the car there is very little to no fuel usage.

You may think the feature is dumb but I think it is brilliant.

 

It could just regen harder if the battery is not full (2 bars from top). Instead it'll spin the engine and not really charge the battery even if it is mostly discharged? Have not extensively tested yet. Car could just behave like normal and regen harder to maintain speed down a hill as best it can and spin the engine like it normally would if the Battery Management System says that it cannot charge anymore.
Engine on/regen is not a higher torque regen than engine off/regen, in my experience it is actually a touch less. When I am braking down a hill with only full regen, no friction brakes; just on the threshold of full regen, and the battery becomes full (I see the EV indicator go out), the regen affect immediately is reduced a bit.

In short, if the battery can charge, but the car is programmed not to when on Cruise Control, then dumb. Efficiency loss for no reason. 4 wheel disc brakes are more than capable IMO if you need to touch the pedal down a decent grade. The efficiency loss decision can't possible be a 'safety feature'.

 

Again, I have evidence to the contrary every day. Near the end of my commute I have a looong down hill stretch. For most of it the car uses normal regen, then when there is one bar left from full the engine kicks in with engine breaking. If there is enough of the downhill left my battery meter will reach full bars even though the engine is braking, so regen is still occurring. This proves that the car will recharge even when engine braking is occurring. Is it the same amount of regen as with the motor/gen alone? Empirical proof for me every day.

 

This is with cruise control on? Hmm, then your car behaves differently than mine. I could have 3 battery bars from the top with cruise control on, going down a slight hill and that EV indicator goes out when it starts to coast (slight regen).
Simply switching off cruise and coasting with no pedals and the engine is off again. Switch it back on in a way that doesn't cause a need to accelerate (power surge), engine turns on again. Strange.

I think I have tested it with a decent down hill slope.. the car will not 'press the brake pedal' (any more regen than coasting) by itself with CC on, just the slight regen of coasting. I'll have to try this out again some day.

 

IIRC, in cruise control when available regenerative braking is insufficient, my Gen 3 brakes by spinning the engine without using fuel in this situation. It sounds as though the engine is running but there is no fuel use. The disc brakes are applied only when available regen braking plus available engine braking are still insufficient. Are you sure that this isn't what is happening with your Gen 4?

 

@energyandair Your car will even apply the friction brakes by itself when CC is on if it needs to? Well my gen 4 Prius does not.
I know, infinite MPG with engine on i get it. But i'd rather have that energy go into the non-full (1-2 bars or more from top. I know it won't always goes above 2 bars from top if temperature is high) battery.

 

Gen 4 Prius will, in some cases, apply engine braking when the battery is not full, when on cruise control. Disengage cruise control and use your foot on the brake pedal for the same deceleration, and you get no engine braking, and presumably more energy into the battery (because it's not being used to spin the engine). This is consistent with what chughes123 said.

 

I don't recall having to manually apply brakes when on cruise control unless I wanted to slow down but the situation doesn't arise much around town. I'll check when the opportunity arises.

To protect the battery, regen is limited by maximum charging rate as well as by available unused storage capacity. You may be running into the maximum charging rate limit. e.g. On a steep hill.

 

Are you driving a Prius?

Sorry if I missed it, I'm just seeing this:



FWIW, with my 2010 Prius, if cruise is set and I come to a steep downhill, it'll regen break big time to hold the speed.

 

I suspect its already using all of the regen braking it thinks it should, and what you will get is friction braking instead of engine braking with no more energy reclaimed. If so, this would presumably shorten brake pad and disc life.

 

I don't use cruise control.

I was driving at 65 mph, and approached a long, sweeping, gradual downhill of about 5 or 6 miles. I took my foot off the gas pedal and just let the car coast. I was waiting for some kind of "regen braking" to begin, but it never did and the speed reached 94 mph about half way down the hill. All I could do, was ride the brakes down the rest of the hill. It was a little unnerving, as the car seemed to take too long to slow down.

Maybe I am misunderstanding what regen braking is supposed to do.

 

Regen braking works for the most part when your foot is on the brake. Cruise control would have slowed the car with engine braking and filled the battery.

 

I don't like cruise, (mine is not radar) and I've never used it in any vehicle. So I guess the solution for my Prius, is to just be prepared to use the regular friction brakes when going down hills. That's fine, no problem. I'll burn 'em up.

I just wish there was a way to "downshift" the tranny. But there is no tranny.

 

You won't burn your brakes. Gentle braking on a downslope will only engage the regen braking. Once the battery is completely full, then friction braking will occur.

 

Yes, on that long downhill riding the brakes, my battery was quickly overflowing. I tried to brake gently, It was probably all friction for the last couple of miles. No problem, now I know what to expect. But I still wish there was a way to "downshift", like in a regular car with an auto trans.

What if you're going down a steep winding mountain road, for 30 miles? Ride the brakes the entire time? It doesn't feel right to me.

 

You will just have to learn to embrace cruise control!