Mountain driving issues in my 2016 4 touring

Contradiction here. Are you comparing to the Gen3 (2010-2015), or to the 2008 (Gen2)?

The mountain climbing battery behavior you describe for your 2016 sounds similar to what I experience with my former 2010 and current 2012. They don't drop to 2 or 3 bars on the climbs. A switch to tell the car to use up the battery charge on the way up would be useful, but I can also foresee a lot of battery degrading misuse of it.

Regardless of software, a non-plugin hybrid is going to waste most of the downhill regen on those mountains, it simply doesn't have the hardware to store it. Only a true plugin has even battery capacity to handle it.

 

Not much help with the uphill, but on the downhill side I think I prefer using the radar cruise and following someone. The radar cruise will run the friction brakes as well, when relying just on the B mode the engine screams and doesn't provide enough drag to slow me down or even maintain speed.

On the uphill side, I have the same experience. About two bars it kicks on the ICE to charge it up. Although I haven't complained about it because my fear (maybe unfounded) is that I'd run out of electric juice and be stuck trying to rely on just the ICE to finish the long climb. For Mount Evans, could you run it just in EV mode near the top to drain out the battery a bit more?

 

No way could software rescue that situation to more than a minor extent (as it could with fuzzy's hypothetical advance deplete option). Most of the potential energy energy is going to have to be wasted, whether through friction brakes, spinning the engine, or some other route.

My third generation never depletes like that on long climbs. The charge indicator typically holds steady at 6 bar segments all the way up, no matter how long or steep the hill. Descending the same hills, it quickly fills to 8, especially if I don't use "B."

P.S.: I see your correction to 2nd generation. That behavior would be slightly more fuel efficient, but likely harder on the battery.

 

Thanks for the clarification.

The change in behavior that you are observing began with Model Year 2010, not 2016.

 

That is how the engineers set the drivetrain up. In my former Prius c, westbound out of the tunnel, the motor stayed at minimum RPM's until the battery topped out about halfway down the hill, then the motor was called into action with high RPMs to keep the speed at the cruise control setting. My 2016 Eco starts to spin up the motor immediately after exiting the tunnel westbound even though the battery is nowhere near full. I don't get it. I just trust the engineers knew what they were doing. At least the motor "scream" is far quieter than the old c's motor.
My 550 pound heavier 2016 is getting very close to 6 mpg better than the smaller c model driven the same way so I am not complaining.
On steep downhill grades where I know I will have to use some friction braking, I put the "transmission" in the B setting so when I touch the brake pedal the motor does not drop RPMs as it does if I have the cruise control set. I am operating the vehicle on the concept of using "gearing down" rather than using up the brakes.
As to the 48, vs 57 mpg. Do your friends go on the commute with you? That is extra weight. Does your commute involve huge elevation changes? Physics demand that there is no way to recover going down hill what a vehicle burns going uphill. I always get a good 10-15 better if I stay in Summit County than if the tank includes a trip down to Denver and back. So your Mt. Evans trip was lots (and lots) of elevation change with a good load aboard. 48 sounds entirely reasonable. Name another car that would do anywhere near 48.

Re reading your entry, the statement concerning excess electrons, here is a wild guess. The battery cannot be overcharged or otherwise it will be damaged. Perhaps the system revs up the motor for frictional braking, and at the same time uses one electric motor as a generator and the other electric motor as a motor. The two then cancel each other out. One produces the excess electrons and the other uses them.

 

One of my gripes with any of the hybrids that I have owned or driven here in western PA is that the charge management system allows for charging while driving uphill. Heck, my cellphone can tell me if my altitude is increasing in a positive direction while walking, but my car can't and hold off on the charging till the altitude starts decreasing for a given distance. Being from the Lakewood area of Denver I know the distances I travel up and down are not in the same relm but still, when a car tops off the battery after going into charge mode half way up. I feel I lose all the way back down.

 

The ICE bump from 1.5L (Gen 2) to 1.8L (Gen 3&4) made a huge difference in the car's ability to maintain SOC while under heavier loads.

 

I'm half convinced that the cruise is applying the friction brakes as well. I've only gone through the tunnel once since I've bought this car, but on the western drive down from the tunnel into Silverthorne I thought I was being smart by putting it into B. I had my cruise on, clicked B.... well that seemed to disable cruise. So I just rode down in B, kept my foot off the brake and accelerator just letting the car do its thing. I was at 85 by the bottom of the hill with the ICE screaming. Since then I've just left it in cruise and it does a much better job of holding speed although I have not gone down that same stretch of road yet. My theory is that the car will ride the friction brakes to maintain speed. If true, I don't like it as I worry that it could overheat the friction brakes. Using B alone certainly didn't provide the engine braking I was expecting.

I'm heading over Loveland pass tomorrow, bright and early, so maybe I'll get a chance to play with it a bit more

 

There are limits to B's ability to slow the vehicle down. I noticed that on my former Prius c as well.
I always use the cruise control down from the tunnel and the speed holds steady. I hope it is not using the friction brakes with the cruise on. In both cars it seems it is more effective at some time than other times, as if there are some set of factors that determine the B mode's effectiveness.

 

In the Gen3, B shuts off CC.

In my Gen3, I've had a feeling (unconfirmed) that B mode engine braking (after the battery fills) just runs up to a certain power limit, then no more. If I start down a certain 7% grade at the speed limit, it soon runs over and I must apply the friction brakes. But if I start down at just 50 mph, it can maintain speed much better, taking a very long time to get up to 60, where it then starts losing control more quickly.

Theoretically, this makes sense. The braking power needed to hold a steady speed is proportional to the slope (mostly constant) times the speed (neglecting non-linearities in air drag). The higher speed needs higher braking power to hold steady, but the engine can't provide more without redlining.