Is there a legitimate use for charge mode in the Prime?

I can't help it if you have poor reading comprehension. No there is no engine braking in D, it's regen braking, as evidenced by looking at your CHG meter when it happens. Also, if you look at your energy flow screen, you'll note that the engine is not running when you are decelerating. Engine braking only occurs when you select B with the shifter.

 

I see no evidence of any of those many states of drag you envision. They appear to be pure fantasy.
The reality is much simpler, as I have explained it several times, which you appear to have ignored.

 

When I'm proved wrong, I admit it. I don't go away, and come back with some convoluted fantasy to prove I'm correct.

I relied on the advice of two dealers, who both told me my Prius had an AGM battery. It was an honest mistake, and has no relevance to the current issue. To bring that up now is infantile to say the least.

 

This thread has a lot of good info on B mode. Unfortunately @Paul Gregory isn't quite finishing the descriptions of under which conditions he bases his conclusions on. Because under certain conditions his conclusions are correct, but not under all conditions. And I guess Paul expects us to know which conditions he's referring to without telling us.

How long are you planning to spam this thread Paul?

 

I'd like to see some evidence that would show I'm mistaken. All I'm seeing are assertions that I'm wrong. As I've shown before, I readily own up to my mistakes. I've yet to see where I've made one here. Anyone who has read what I posted can see that I've been very clear, multiple times.
You can take back your accusation that I'm spamming the thread. You don't get to say that just because you don't wish to agree with the facts, fella.

 

Paul, you're not the first priuschat member to think that you know how B mode works and everyone else in the thread doesn't know what they are talking about. Besides you're offtopic in a thread titled Is there a legitimate use for charge mode in the Prime. Like anyone ever pays attention to thread titles here anyway.
OK Paul, you're right B mode only functions the way you say it does. Happy now?

 

Second time on here I got cornered by fools who thought I had my facts wrong.

 

I think that the easiest way to prove PG wrong is to look at his assertion that a car will accelerate forever and then attributes that to the law of physics. That's just plain wrong in any earthly environment. The car is slowed by the rolling resistance of the tires, bearings and other running gear. The car is also slowed by drag in the guise of air resistance.

The other way that PG is wrong is that he thinks that he's right, even though he ignored one of the established members of the board when they pointed out the fact that all cars sold in the US have to have something similar to the PRNDL gear shifting arrangement. There are several arrangements that are approved and one of them must be used.

In short, Paul Gregory thinks he is right when he is wrong, so that means that he has failed to admit that he's wrong in just about every post.

 

That is mostly right. However engine braking, aka B mode has it's limits. It's primary use it to assist the friction brakes when going downhill. Not the other way around like the sentence "Applying the friction brakes for long periods will destroy them, so the only option left is engine braking." would let believe. If the friction brakes are toast, it's kind of too late and chances are engine braking won't get you out of a dicey situation then.. So the proper use of B mode is (1) Apply B mode. (2) Modulate with the brake pedal.

P.S. Never had to use B mode with my 2024 Prime. Used it once or twice with my 2021 and was "Meh.." and then, never used it again..

 

If you never need to use the B engine brake, that's the best scenario. But it's there if you find yourself on a long downslope, and burning up your friction brakes is your only other option.

 

I've been on hills where the car continues to pick up speed without any braking. There is nowhere near enough rolling friction to prevent the car from picking up dangerous speeds. Just because you haven't encountered such a hill doesn't mean they don't exist. It's just a fact that such hills require an engine brake. Disbelief is not disproof. You should know that.

I don't know anything about the PRNDL layout. It doesn't matter anyway, it's a CVT transmission, and if the emulated L gear does the trick for you, all the better. But it doesn't make me a liar.

How do you suppose I failed to admit I was wrong? Show me any mistake I made, and I will correct it. You just saying I failed to admit I was wrong in "just about every post" is a flat-out lie.

 

Read the portion of the Owner's Manual copied and attached to Reply #64. It has a section labeled "Regeneration Boost", and very distinctly show 3 levels of B.

I grabbed an e-copy off his OM from Toyota's website, and verified for myself that what he posted came from Toyota's Manuals & Warranties webpages.

Why do you appear to ignore this portion of his Owner's Manual?

Your profile shows you owning a Prius Prime. Is that incorrect? From your recent replies here, it seems that you are writing about regular non-plugin Prii, not about Primes.

 

Are you saying that when it appeared that my 2010-12 Prii went into engine braking in D mode (at low speed, below the ICE-auto-off threshold), that my ScanGauge-II was lying when it showed ICE spinning somewhat over 1000 RPM? And my HSI meter was lying when the CHG bar vanished?

D/Cruise Control did this also, though with much higher RPM.

I abandoned the energy flow screen after a week or so of first Prius ownership. The HSI screen was more useful. And a ScanGauge-II revealed the ICE always spinning when vehicle speed exceeded 46 mph, its ICE-auto-off threshold. Later generations were able to push this threshold up to 60-80 mph.

Both D, and Cruise Control, gave me engine braking in my 2010-12 Prii, as very clearly and unambiguously revealed by a ScanGauge-II's RPM display.

None of these were my own discoveries, but had previously been covered and well explained by old-era HSD experts here. You would do well to go back and read them yourself.

And now in my RAV4 Prime, the tachometer (an optional available choice in the optional HUD) has clearly revealed some engine braking in D, as I was initially learning about its regeneration and battery management.

 

So that you have more choices to control the degree of engine braking. And to obey federal law.

Two weeks ago, I rolled down a 31 mile downslope, with 3400 feet elevation drop. Cresting the top with 9 or 10 EV miles showing, it quickly added some more miles on the initial steepest segment, but never filled the traction battery. Not even close! Those EV miles where then enough for propulsion on the shallower slope farther down, where it wasn't inclined enough to glide, and to (barely) get to the day's destination (and a charge station) without ever spinning the ICE after the mountain pass.

Why drain the traction battery first? To get as many EV miles as I could on this trip segment, to reduce fossil fuel use. I started from home with a full charge, consumed it all before reaching the base of this particular mountain segment, added 10 new EV miles from a charging station at a rest stop, saved it during the mountain climb by selecting HV, then went EV when cresting the top.

Result? 52 miles of plug-in charging in two charge sessions (on a 42-mile battery), plus downhill regeneration, produced 73 actual EV miles, and zero engine braking, with 1 more EV mile still remaining in the battery. Had I 'saved' most of the original home-charged miles and crested the mountain pass with a mostly full battery, then I'd have produced only 30-some EV miles, lots of engine braking, and consumed about an addition gallon of gasoline (EPA highway rating of this AWD SUV is 36 mpg, but my real-world is low 40+ mpg).

How ridiculous is that?

Prior travels took my regular Prius to even longer downslopes with greater elevation drops. But this Prime hasn't been to them. Yet.

 

How can a person drive an automatic transmission without knowing about the park-reverse-neutral-drive-low shifter layout? that's PRNDL to most of the world. It's affectionately referred to as "prindle" in my family. It's one of the allowed shifting layouts in the US.

Where is this hill where "the car continues to pick up speed without any braking"? The GPS coordinate is enough. No need to get fancy. BTW, don't forget that this thread is about the Prius Prime, not some other, older or different car.

 

I agree! B mode really is a brake helper. Do not rely on it for your life though.

 

If you can settle down from throwing out continuing ad hominem, I have a test for you to try. After you post your results here, I'll link you back to some of my past test result postings, so we can compare.

On one of your long B-mode descents, after the battery is filled up from regeneration and the ICE is in screaming engine braking mode, read the engine RPM from your favorite tachometer application or device. I used a ScanGauge-II on the OBDII port in my regular old Prius, many other people have newer Bluetooth dongles connected to better mobile apps reporting similar or even more information from the same databus.

Then, switch to D-mode for a little bit, long enough for the ICE to either settle to a lower RPM (as mine always did), or 0 RPM (as you claim for your newer generation, my Gen3 couldn't do that above 46 mph). But not for long enough to roll up to dangerous speed, switch back to B-mode to safely control speed. Repeat this cycle several times, reading RPM in each mode, and report those numbers back to this thread.

Also, feel if there is any engine drag while in the D-modes of this test. If not sure, then try some N-mode too for comparison.

After that, I'll link you to my past results. If you haven't found them already, via the Search feature. I haven't yet tried this or equivalent on my new Prime.

 

Crickets?

Or just taking a long time to respond?