HV using EV capacity

So what I'm wondering is, if you're driving your PiP at 60mph ... level ground, HV ... while the ICE is spinning at less than 1963 rpm, would your mpg's be the same as a standard Gen III?

 

I believe the PiP tries to alleviate the "first minute blues" by continuing to run on battery while the warm-up is in progress. If you demand more power during that period, the ICE will still assist during its warm-up, but if the car can do without the ICE, its seems to continue running on battery as long as it can. The HSI display will still change to the "HV display", but it continues to run just on battery.

Using Torque, I've consistently seen that when the SoC reaches 23.1%, the warm-up will begin. I've seen the SoC drop to as low as ~18% while warming up. I've never see it go lower, so I think its this "extra" ~5% that it will continue to use as long as the power demand during warm-up isn't significant.

 

if you are in HV mode, completely warmed up, and running in the non-ev area then it pretty much holds the charge, within a couple of percent. pretty much the same as the regular prius.

 

Thanks pfile, but I find that explanation confusing because the regular Prius does not try to hold any old SOC, it tends to drift towards a quite delimited SOC neighborhood of (somewhere) around 55%, and as the SOC is further from target the tendency to move towards target increases. Is the PiP doing the same, with the same SOC target ?

 

well as far as i can tell, it is holding the SOC that it was left at when you exited EV mode, plus or minus a little bit. if it's left to go all the way down to the 23% range where it exits EV mode (showing 8 bars on the battery, like the regular prius) then it seems to drift back up to about 25% (still showing 8 bars) and hover around that point.

so i guess i meant "like the regular prius" if you've exhausted all the EV range. in this case though the SOC isn't 55% but it still shows 8 bars, so i guess 25% is the new 55% if that makes sense

 

hmm.

Perhaps someone could try this experiment:

1. Charge up the battery
2. From start, drive in HV mode 13 miles a mixture of city and highway without hypermiling. Just 'normal' driving.
3. Report EV range

 

Yes, should be the same. The battery would not be in use, unless there is some elevation changes or gusts of wind.

 

my experience above is based on a trip to work (45 mi, where 40mi is freeway driving) where i decided to just use HV mode almost exclusively. i started off in EV mode and got down to about 8.7 miles of EV range remaining, then switched to HV mode on the highway and left it in HV mode. the trip down 13 to 580 is mostly downhill and by the time i reached 238 i had regenerated a little bit of charge, so the range meter showed 9.2 miles. it remained at 9.2 miles until arriving at work. the last 2 miles of the drive are along city streets with 40mph speed limits. i did not try to pulse/glide or otherwise stay in stealth mode during the last part of the trip; i "just drove it".

my conclusion from all of this is that 1) the PIP holds the charge where you exited EV mode (as long as the engine was warm when you exited, or else it will use more electric power while the engine is warming up), and 2) if you want HV mode + extra electric assist, you have to be in EV mode and going > 62mph. if you drop below that speed chances are the ICE will stop and you'll be back in pure EV mode.

 

whew! my head is spinning! I've been reading these posts, trying to ferret out the info I need and the terminology and multiple modes have me confused. I only have a few short commutes and one long (200 mi) trip on my PiP, but my question revolves around EV mode. What I don't understand is why it didn't charge when I took my long, freeway drive. I just left the button in EV mode, but when I arrived at my destination, the car stayed in HV mode, even at low speeds. When I hit the EV button I got a message saying the EV battery was too low. I see some messages above referring to maintaining a charge on the EV, or driving at low speeds to charge the EV, but even after I got off the freeway, I saw no charging of the EV. So are there two separate batteries (EV and HV)? How do I maintain a charge or recharge the EV without carrying my plug around?
Thanks for any answers to my obviously naive questions,
Tom Farr

 

Hi Tom,
I'd like to answer your question, but I'll need some clarification first.
Did you begin your trip with a fully EV charged battery?
Now, one part of your comments is not clear. You say you "left the button in EV mode" ....
Well, the EV/HV button is just a toggle, it doesn't have a set position.
Did you ever push the EV button at any time during your long drive?
Or are you saying you began your trip in the default EV mode, and let the car switch over to HV mode when your EV range depleted? And then finish the trip in default HV mode, right?
What speed were driving on your trip?

 

I don't follow conclusion #2. Can you please explain what you're saying?

 

what i mean is that when the car is in HV mode, it behaves pretty much like a regular prius (except that it does not seek the goal of getting the battery SOC to "8 bars" like the regular prius does). so the electric motor assists a little bit depending on how much power you have asked for, but never a whole lot.

if you are in EV mode > 62mph and requesting power, the electric motor will output a whole lot more power than it will in HV mode, but the ICE will also be providing power as well. of course it is "EV mode" after all, so if you drop your speed below 62mph the ICE may just shut off. i can see on my scangauge that the battery current when in EV mode > 62mph is much greater than when in HV mode at highway speeds.

i guess in my head i had hoped that the PIP might have a mode where it uses the larger capacity of the battery to allow lower ICE power output, but as others have pointed out the ICE is only really efficient when it is running at 'high' RPM, so the way they have designed it is probably correct. my wished-for mode only exists when the demand on the ICE is high enough (and therefore can operate most efficiently), which is on the highway at greater than 62MPH.

 

Generally, plugin hybrids will not automatically recharge the EV battery intentionally by running the gasoline engine (beyond the 300-500 Wh they need to maintain for hybrid optimization) although regenerative braking may recapture some energy. The reason for this is that generating and storing the energy from the gasoline engine inherently loses some efficiency. It is generally more efficient to just use the gas engine directly as needed to drive the car while just maintaining 300-500 Wh of battery buffer to gain the usual hybrid efficiency. Generating more power than that to fully recharge the battery is generally less efficient. Also, charging the EV battery from the utility grid is usually much cheaper and could emit less pollution.

Some plugin hybrids, like the Volt, can optionally generate power from the gasoline engine to at least partially recharge the EV battery ("Mountain Mode") but as far as I can tell the Plugin Prius does not do this and does not need to since its gas engine is larger than the one in the Volt and it powers a lighter car during grueling mountain pass driving at high speed.

 

Pardon my ignorance - I am not Prius-experienced. But going back to the OP's observation:

Does this PIP stealth mode mean that there is no way to turn off EV mode completely?

For example - I am in traffic at a steady 40 mph, but I know that later in the trip there will be 5 miles of city stop-and-go. So I want to conserve EV capacity for that (if I'm correct) more efficient use. But the PIP won't let me. Am I understanding?

Maybe the moral is that the PIP knows how it wants to use EV capacity, so sit back and enjoy it? (Even if you know more about your trip itinerary than it does.)

 

Careful.... Just based on that information alone it doesn't necessarily follow that the EV range estimate change from 8.7 to 9.2 means that some charge was regenerated into the battery. It could mean that the computer that estimates the EV range just noticed that you were recently driving more efficiently (downhill) and therefore your same usable battery charge might allow you to drive farther.

In other words, the EV range meter is not a battery State of Charge meter -- it is an estimate of how far you can drive based on a variety of conditions including your battery charge.

 

Which brings up another question (and apologies for starting to drift OT).

I don't drive every day. So rather than always plugging in and automatically charging at 3 am the next morning, will I extend the battery life significantly by using my smartphone to charge in the morning of the day I know I'll want to use the car? (And do the apps have that ability? Day-of-week programming would be helpful ...)

Or - since I only drive about 6000 miles a year - will my battery life be enough longer than normal that I should - again - just sit back, relax and enjoy, and not worry about optimizing?

 

How sure are you that 82% and "9.9 miles" is the happy state? Is it possible that if you continued driving in HV it would continue to gradually use up battery charge? Did you drive far enough in your test that you are confident that it drained down to 82% and then held it there as you continued driving a substantial additional amount?

 

If you want to conserve EV capacity, then switch to HV mode and drive. But its still going use some battery capacity since it's a hybrid in HV (hybrid vehicle) mode. Then switch to EV mode when you get to that stop-and-go traffic.

 

Right, I didn't intend to leave that impression, I just meant that plugin hybrids generally would not automatically generate more than the 300-500 Wh of hybrid mode battery buffer that they need to maintain on average for hybrid optimization purposes. I can see that I was unclear about that. I'll go back and fix my post.