What Exactly does EV Auto Do?

Who me?
As I said, I think EV auto is like PiP EV (as trollbait put it somewhere earlier) only with much higher threshold of torque demand to fire the ICE and resuming EV drive once ICE is not needed
When the threshold is high some with light foot and short experience may conclude it never needs the ICE.

I also believe that unlike Prime's EV mode, this mode is not dual motors drive and it uses MG2 only (one way clutch is not engaged) like the PiP and if this is true, we can assume 53 kW max for EV drive in EV auto (the threshold) as compared to 38 kW with the PiP (PiP threshold). But I don't have any reference to this, just makes sense to me.

 

thanks, i think i finally understand.

 

EV Auto is just like the EV that you have in the PIP.
Prime EV Mode, not EV Auto, doesn't try to start the ICE unless you exceed 84 mph or you run out of battery.

 

If you want another data point my typical drive to town is with a full charge in EV mode, a steep but short uphill run (3/8 mile) bringing the charge down to about 90%. Followed by 3.5 mile downhill section with a elevation loss of 1200 feet which brings the charge back up to 100%.

Today, for instance, it was about 50 degrees with the heat set at 70 degrees and the ICE came on about 2/3 of the way down the hill while still in EV. I noticed it when the silhouette of the little car in the HSI indicator changed color to black. Switching to the screen with the little arrows flowing I could see the engine on with arrows flowing out, but not all the time. By the time I got to the bottom of the hill the silhouette had turned back to colored, all the while in EV. MPG reading remained at 199.9. Top speed was less than 35 mph for the trip and very little throttle added after starting down hill.

On edit: I made a mistake on the MPG reading. I forgot to reset the trip meter at the start of the run. Today I did it again with the trip meter zeroed and the MPG went down to about 150 or so. So it looks like then ICE did use some amount of fuel.
Sorry for the bad information.

 

Maybe my interpretation of the manual is somewhat oversimplified, but the way I read it is that EV Auto is mostly about what happens when you floor (or nearly floor) the accelerator. Under ideal conditions in EV mode, ICE will not fire when you the floor the pedal, although this can result that the car may seem slightly underpowered. Whereas in EV Auto, under the same conditions ICE will fire when you floor it, providing the maximum power that the Prime is capable of.

So for maximum efficiency you would never use EV Auto, only EV or HV. But if you feel that the car seems underpowered under hard acceleration in EV mode, using EV Auto may help. And which in theory shouldn't affect efficiency that much assuming that you are only flooring it in relatively rare circumstances, and only briefly.

Perhaps causing some confusion is that as a separate topic, in EV mode there are apparently a number of variables that in certain combinations will cause ICE to fire even when you still have EV charge. But in most cases this would be unrelated to whether or not you are in EV Auto.

 

If I understand correctly, what you are describing is not new and was already discussed for long in the PiP forum.
In short, ICE turned on by the system to protect the battery from being overcharged by 'purging' some charge so that the charge in the battery will not exceed 100% by the regeneration in the downhill.
By more than 100% I mean more than the full charge at the beginning (not to be confused with 100% SOC).
Many PiPers with similar situation reported the same. It is done to protect the battery.

 

To the O/P question:

1. A driver who mainly cares about efficiency. Light foot. But in the very rare emergency situations wants all the power available.
Probably this driver will not see difference between EV and EV auto modes regularly, in both he will not trigger the ICE. But in emergency he will have the full power the car can supply...in EV auto. So the best mode for him is EV auto isn't it?

2. A driver who mainly cares about performance. Heavy foot. In EV auto mode he will probably trigger the ICE several times in a trip due to power demand. HV mode is not a good option for him as long as he has charge as he does care for tailpipe pollution. The best mode for him is...EV auto isn't it?

I think EV auto is best mode all around, one may ask: why EV mode (and not EV auto) is the default mode then? I suspect it is surrendering to the market request/demand and trying to be mainstream, after all many (most?) of PHEV buyers want to see their car as BEV with range extender isn't it?

 

no. it won't start the ice unless you press hv, or put it in charge mode or it need to protect the battery for one reason or another, or you press front defrost, or the temp is below 14f, or who knows what else. not sure about hv auto yet.

 

odd that it came on ruing the downhill, any idea how many miles you burned off on the climb?

good to know it doesn't go into warm up mode like pip.

 

1200 ft in 3.5 miles is a 6.5% grade ave. A common slope and distance for I-68 in Western Maryland. Would be interesting to known what kWh it takes to get back to the top of this Mtn. There is a trip meter and a display screen buried in the menu options that look like it could be used for this. There is also one that looks like it measures regen also. Maybe charge mode too.

 

That is what a blended PHEV is, as oppose to an EREV one like the Volt. The car will try to stay in EV operation, but the EV side of the drivetrain can't meet the car's total performance alone. In times of high torque demand or exceeding a max speed, the ICE comes on to help. A Prime on EV auto should operate like an Energi; ICE on for high torque demand, and the top EV only speed can be lower than the EV mode's.

In terms of resources available to the car, EV auto will be the most efficient. The Prime has 25 miles of EV. By using the ICE on hills and passing, those EV miles could be extended to 30. This could lead to being more efficient overall. The gasoline burned under high demand times isn't the most efficient use of it, but neither is it an efficient use of grid charge. Burning the gas then means more gas free EV miles during the rest of the trip before charging.

As with basic cruise control, and alert driver can out perform EV auto by switching between EV and HV modes manually, but that does mean more work for them. There are smart versions though. Ford plug ins, and maybe the hybrids, can learn common destinations and routes. When approaching home, the car will make more use of the grid charge, if any is left, in order to have an empty pack to fill. There is also work going on with GPS systems that will let any car on cruise control to tackle hills better.

 

But only for trips where you expect to go beyond EV range, correct? For trips that can be done within EV range, or where at-work charging makes a full EV trip possible, then you would not want ICE to fire at all. You would keep it in EV for the entire trip and accept that hard acceleration and aggressive hill climbing will take a performance hit. But for longer trips beyond EV range where you will be strategizing the use of the EV charge, then yes I can see how EV Auto would be another one of the available tools in the pouch.

 

yes

 

I missed the discussions on the PiP forums, I am a new to Prius the Prime is my first. But yes, as you stated, the system started the ICE when the battery got to 100%.

I wonder how running the ICE stops the charging? Seems like the generator would just be taken off line; the gererator does seem to be variable.

 

If you use the forward motion of the car to spin the ICE, it's the same as the starter motor in a regular car starting the engine - it draws a lot of power to spin the engine. Spin it faster, and it draws more power. Thus, it can restrain the car without using the friction brakes and without charging the battery. This can be done by controlling the two electric motors so that one draws power from the wheels and pumps that power to the other one which spins the engine (I'm over-simplifying).

 

I was under the impression that charging for breaking stops, and the ICE is used for breaking, basically by turning the ICE into a air compressor, and this heated compressed (heated by the act of compression) air is dumped in the exhaust.

So it's not really ICE stopping the charging. The car decides not to use charging for breaking any more, and to use engine breaking.

 

Wow, there are a lot of information being discussed in this thread, but let me throw this into the mix for what it's worth ...

I drove to office today on my normal route, but instead of HV, I used EV Auto. I got on the freeway and set Cruise Control around 6x MPH, and increased it to 7x and noticed it tends to kick in around 72-73 MPH when driving on relatively flat surface. When I was heading up a hill, probably around 5 degree incline for about 3-4 miles, the ICE was on the entire time while I was driving around 7x MPH.

However, if I step on the gas pedal pass maybe around 1/2 way, the ICE would kick on as well even when I am driving at a lower speed.

If this was HV mode, ICE would be on most of my daily commute trip. I would probably starting using EV Auto a lot more now as it seems to be able to balance EV/ICE driving pretty well even just with my one trip.

 

5 degree incline? Do you know how steep that is? It's an 8.7% grade - steeper than anything allowed on an interstate.