? about Regen Braking and Gliding to Hybrid and EV Battery

This is a great question! It seems like any time the HV battery is full any excess energy (from the regen brakes or the ICE) should be redirected to the EV battery.

Can any Pip owner confirm this?

Thanks to everyone for joining in!

 

I am confused by the terms EV battery and HV battery. Isn't there only one traction battery in the PiP?

 

I think a Senior member might have a better answer for this but you might Wiki Prius Plug In and review the section under Specifications... It does a pretty good job of describing it.

 

Anytime that the charging side of the bar is lit, it is charging the batteries. If you are in HV mode (fully depleted EV battery) it will charge that, and then charge the EV battery. However, unless you have a very long downhill run with some heavy regenerative braking, not sure that you will add much more than a few tenths of mileage back to the EV battery. When the EV battery is depleted, it automatically switiches to the HV mode. Not sure if you would have to push the button to switch it back to EV (if there is a charge to use) or if it would switch back automatically.

 

The production version of the PiP only has one battery. When fully charged (to the maximum level Toyota allows), the full EV charge is available. When the majority of the charge is depleted, the battery then operates as if it is the normal hybrid battery found in the standard Prius.

If you do a lot of braking/regeneration (or go down long hills) you could boost up the battery's charge and have some more EV charge available.

Note: It would be foolish to try to create this energy by braking more than you need to (since you don't get all this energy back)'!

 

Physically, it is the same battery pack. It is logically different in term of SOC range. The screen shows the battery as one solid block in EV mode but it shows 8 bars in the HV mode.

 

It seems like the other component of this question could be that if you're driving on the highway you have the potential of using the ICE and that operation could also contribute to charging the pack in addition to the brakes...

 

I haven't driven far enough (in one trip) and I don't cover enough elevation to see this happen. So far, for me, once I've depleted my battery into the HV only range, I havent been able to regen enough to get any EV range. I've had a full "HV battery", but I have never seen any EV range appear after that point.

But like I said, I don't really cover much elevation. My home is at 465 feet. I live about 15 minutes from the beach so most of my driving, once down the hill from home, is all flat and nearly at sea level.

When in EV mode, I've seen it regen 0.2 to 0.3 miles of range just coming to a stop. It seems like it should be possible to regen enough to get some EV range. I think the Cajon Pass would be perfect for this test.

 

This is true. Think of the Plug-In as a Hatchback Prius with a bigger battery that can also be charged by plugging into AC power.

 

Thanks Jim, that helps and does make sense. One thought I have is related to some of the early PiP deliveries at the end of last week. A number of folks mentioned that they received their PiPs without a charged pack. They then drove home, sometimes driving on the highway, I wonder if they noticed that their range increased while driving with the ICE running? I wonder if their battery indicator transitioned from the HV battery mode to the EV battery mode indicator (striped vs. non-striped)?

It will be interesting to see how much increased EV range can be gained from the regen and the ICE for a given drive.

Thanks again -

 

Personally, I don't foresee the PHV Prius spending any gas specifically to recharge the battery for EV driving. Yes, to send some electricity to the battery to support HV driving, but that's it (just like in a regular Prius). If anything, the ICE would once in a while get "help" from the EV side, but not the other way around. It is not an efficient way to spend gas. Battery charging for EV use by design comes form the plug, or braking regen if HV charge is already maxed out.
This is just my understanding of the Prius logic...

 

Wouldn't you need to push the EV button again to see EV related range indications once the car has dropped into HV mode? Maybe it is charging the battery enough to have EV range, while driving in HV mode or via regen, but it's not seen because EV mode needs to be selected.

 

Thanks...all are excellent points. The scenario I was wondering about was the following: I'm about 9 or 10 miles from a nearby highway and I'd expect to use the majority of my EV miles to get to the highway. Then I often drive about 60 miles into the city that is near my home. My speed would be ~70 MPH. I was wondering if I could charge my (future, I haven't ordered it yet) PiP beyond the HV SOC and actually boost my remaining EV range when I arrived in the city from the ICE running the majority of the 60 mile trip. I'm not sure but it's an interesting notion. Thanks again...

 

I basically posed the same question in another thread today that was hijacked.

Good questions I think.

 

I don't foresee this being a possibility. When the ICE is running, particularly at highway speeds, battery power is blended in for maximum mpg efficiency. If you still had a mile or two of EV range left when engaging HV, then that extra bit would get used to make the ICE more efficient, until reaching a steady state where it is neither charging nor discharging on the flats, leaving a reserve for hills and acceleration. Any charge captured by regen is sent back out at the best opportunity for ICE efficiency gains.

Another issue is that the car most likely will limit the amount of charging current. As SoC gets higher, maximum regen current will push the charging voltage of the cells over a pre-determined limit, so the computer will scale back the amount of regen current allowed. Fast charging is really hard on rechargeable batteries. Let's have someone come down Cajon, Tejon, Tehachapi-Bakersfield, or the back side of Big Bear-Lucerne Valley (Highway 18) with a Scan Gauge and report back with observations for SoC, voltage, and current.

 

Well, here are the behaviors that I have experienced:

1. When I manually switch to HV (by hitting the EV/HV button) with remaining EV range, the EV range will still show. So I've driven around town in HV while still having stored EV range. In this case, I have seen regen increase the EV range. EDIT: I just read the posts above and I should clarify that I have seen the EV range go up AND I have seen it go down (blending).. and I will also add that most of my regen driving around town is through braking. Also, I havent driven on the freeway while retaining EV range. I will try that when I drive home tonight.

2. If I deplete my EV range and the car automatically switches to HV operation, I have seen the "HV battery" (the battery icon with bars) fill up to the top, but with no EV range present at all (no text, no indication of EV range or anything on the MFD). If I hit the EV/HV button under this condition, a "window" will appear on the MFD that says there is not enough charge to switch to EV operation.

3. While in HV operation, the HSI has a line down the middle. If the "power demand" is to the left of the midpoint, the car will start off in EV, say from a traffic light, the same way I believe a non-plug Prius would. Once I pass that midpoint, the ICE turns on. So its just like the non-plug EV experience (as far as I know, since I havent spent much time in a non-plug Gen3). This behavior is consistent regardless of whether there is EV range left or not.

4. If the car is in EV mode and is forced into HV operation (by exceeding 62mph or by high power demand), as long as it remains in EV, it seems to try to go back to EV operation as soon as possible. So, if I speed up to 62mph, then slow down to 45mph, it will go back into EV on its own.


What I havent seen myself is if I had a full HV battery, and I had a good regen opportunity, would it turn into a "EV battery" and start displaying EV range. I havent been in a situation to see if thats possible, mainly because when I see the full HV battery, its only for a short period of time before it goes down again (just driving around town).

In an earlier thread I said I never drove more than 40 miles. I realize that was incorrect. When I picked up my car with no charge, I drove home from Carson Toyota (about 45 miles). It was my first time driving the car and I was getting used to the car and its controls, so I dont recall the HV battery icon ever being full. But I wasnt really paying attention to it either.

 

Excellent info. Thanks. I wanted to ask about manually selected HV mode vs. EV charge depleted HV mode vs. speed transition HV mode. You covered it all.

The observation that while in HV mode, with EV charge remaining, will allow EV charge to increase/decrease is very interesting .
And if the EV charge is depleted it's just normal Prius.
That could insinuate that it may be better to not deplete EV range before getting on the highway.
It also could imply there are 2 kinds of blending built into the car. Blending based on a speed transition, if HV mode happened automatically with EV range remaining.
And blending based on efficientcy if HV mode is manually selected with EV range remaining.
Will have to explore this more.
It implys the possibility of blending in HV mode, and a kind of pre. production Pip behavior in that condition?!
Is funny how complicated this can get.

 

I have been driving the last two days without any EV charge and have observed what you mentioned above multiple times. When the HV display is near full (Almost 8 bars) and you go downhill you will see the 8 bars change to a "EV battery" though with a narrow band of charge. As you continue downhill the ev range displayed increases.

Even though I have been driving without charge the HV battery remains near full 8 bars. What I remember from driving the regular Prius once is the Bars there deplete quickly to low levels. Do these 8 bars in Pip match with 8 bars in Regular Prius?