Switching to HV mode should stop the "miles remaining in EV mode" from decreasing, right?

I agree with this in general, but whether it replenishes the EV range or not is quite dependent on how you are driving the car and the terrain, etc. It may or may not actually try and regain all those miles, IMO. In general, acting like a normal Prius, it "tends" to try and maintain the battery at that point...but I've found (sometimes) that you can use up 1-2 EV miles during the warmup and never get them back...and other times you get back more than you started with.

Mike

 

I recently went on a 240 mile trip from the Sacramento Valley to a lake in the Sierra Nevada Mountains. I didn't record the data but it went something like this. Start with a full charge EV miles reads 12. Use about 4 EV miles getting to the highway. Then HV at 55mph for 70 miles keeping about 8 EV miles, use another 2 EV saved miles in a town before starting up the hill. Arrive at the lake, at that point the HSI reads 50mpg. Use most of the 6 EV saved miles on side trips and starting back home. Down the hill back to the valley I got a full charge to 12 EV miles (85% SOC), used almost all of the EV miles in flatland towns and returning home from the highway using HV on the highway to save the EV miles. So with 2 full charges, one from the power line and one from regeneration the result was 63 mpg for the trip. Of course you have to decrease that by the "energy cost" of the original charge and the fact the HSI mpg is usually about 2 mpg high.

My experience from similar trips in a Prius Three resulted in about 56 mpg on the HSI. So the initial charge and large regeneration capacity of the Plug-in Prius are a real help even for long trips.

 

my car doesn't make up the lost ev miles. today i left with 16 ev miles. immediately put it into hv and drove off. it dropped to 13 and stayed there over the next 30 miles.

 

I drive 14.6 miles and therefore always use some Gas.
Going to work I drive a very level road for 3 miles and driving home I drive a 65 mph highway for 3 miles.
I press button to HV during these stretches and I regain any battery used during warmup before the end of the stretch. I then switch back to EV and finally run out of battery just before getting to my destination.

If you press the button to switch to HV, and drive for 3 miles, the PIP will regain Battery used during warmup.
If you instead shift from EV to HV because of over 62 mph or going into Power Zone, you will use Battery during warmup and NOT get it back. That's the difference between using the EV to HV button or staying in EV and shifting to HV mode.

 

I'm also still having trouble replicating what others say here, and I'm not sure whether it is a) something to do with my driving, b) a difference between the US and UK models, like the lower speed we switch out of EV mode, or c) just that I am misunderstanding what is being said?

When the rest of you are talking about EV miles left not reducing, are you assuming a particular minimum speed? If I switch to HV (press the button so the little EV lamp goes out), all that it seems to do is to reduce the speed at which the car switches over to using EV mileage - about 48mph nominal as opposed to 58. But if I drive at say a steady 40mph, my EV mileage remaining steadily drops, and keeps dropping the further I drive. It may recover sometimes when the ICE comes on. Is that what happens to others?

 

Prius PHV is a plug-in hybrid. That means the engine shut off when it isn't needed.

While in EV mode, you are telling the system to draw as much electricity from the battery-pack as possible. While in HV mode, you are telling the system to draw less. Switching modes changes tolerances, it doesn't prevent.

As some have pointed out, even while in HV mode, estimated EV range will slowly drop. The system is seeking out efficiency opportunities and taken advantage of them when they are found. That's what is suppose to happen.

This is why there is still an "EV" symbol even while in HV mode. When it illuminates, that informs you some capacity which would otherwise be used for EV is being consumed. Technically, that actually is EV mode, since the engine isn't running. To avoid confusion, as it is a feature of HV mode available in both the plug-in and regular models of Prius, those of us wanting to keep things straight call that STEALTH mode.

 

Ah, got it, sorry for being obtuse. Also explains why Bonefish Blues and I felt we couldn't replicate stealth mode; the European parameters look as if they are set differently to the US version, and stealth mode cuts in at a much lower speed (one that it is difficult to keep to on a motorway).

I don't suppose anyone knows what the North American model is supposed to produce as grammes of CO2 per mile or kilometre traveled? I did try to find a spec sheet with it but couldn't. Since that is an important measurement in Europe (including the UK) my working hypothesis is that they tweaked the car to get us below 50 (the European model is 49 ...).

 

In a number of long trips I find I can "save" most (but not all) of the EV miles when I switch into the HV mode. As an example if I switch into HV when the EV miles are 7 it will drop to 6 and pretty much stay between 6 and 6.5 for many miles. As an example on a recent trip I "saved" 8 EV miles for use 70 miles later.

There is, however, a catch. If the SOC is above 75% (perhaps represented by 12 EV miles) and you switch from EV to HV the car will use the battery charge to get down to SOC of 75% (or a little less) and you will lose those 2 miles (12 down to 10 EV miles) that you wanted to save.

 

Yes it will not give you back a "full" battery in HV mode, you must use enough EV to get down to approx 70-75% SOC. I have experimented with this many times.

I leave house with 14.7 EV miles, I start in EV and let it run down to approx 11.5 EV remaining, at this point if I switch to HV mode, the EV miles will tick off another couple miles, but once warmup is done HV mode will recover or give me back all those EV miles back to 11.5 or darn close within .1

Now if i do exact same trip, but push HV right off the bat at 14.7 EV. It will tick off a couple miles for warmup, but NEVER recover back to 14.7.

So the key here is to let EV miles drop to approx 75% SOC.

Dan

 

Since "full" is 85%, that isn't big deal.

 

okay, but that is not the situation i described or o/p asked about.

 

Another thing to keep in mind is that when EV miles drop and are replenished in HV mode, it's not 100% efficient.

Granted that the PiP is probably smart about the most efficient time to skim off some power to store in the battery. But there has been some discussion that the best overall strategy might be to go into HV mode, wait until the EV miles have bottomed out, then go briefly to EV and back to HV to clear the "debt".

 

I believe that is the wrong way around. When you go into EV then HV you set that as the new HV working average point. That makes the "bottomed out" lower number of EV miles the HV working average.

It is the opposite of "stacking" where you go into EV when you can regenerate then back to HV to save the higher EV miles as HV working average point.

 

Yes. What I was suggesting was that it might be more fuel efficient to accept the new lower HV working average, rather than encouraging the ICE to burn more gas to bring the EV miles back up, and then using those EV miles to move the car.

But wouldn't you only do that when you were going downhill and using the wheels to (re)generate power, not the ICE?

 

Yes! Using the ICE to charge the battery is not efficient, regeneration going downhill is wonderful.

 

Then when I said

what was wrong with that, since we agree that having the engine owe the battery EV miles is inefficient?

 

Is there a benefit to 'conserving' your EV miles other than for 'scoreboarding' your higher EV mileage? I mean if I know on a 70 mile trip I'm going to use ALL my EV miles. Does it matter if I use 'em on the highway or slower side roads? Will my MPG be the same at the end?