Regen: the AER booster

VW paid out Mega bucks in judgements to have high MPG figures for their diesel cars. They could tune their cars for minimized pollution or higher mpg. They picked MPG. The stakes are high.

 

The situation is that the Battery is fully discharged and defaulting to full hybrid mode (Any EV or HV-EV mode is totally a different situation).

 

My Prime does seem to charge the battery more aggressively than the PiP did when driving in HV mode. But I assume it's that this system is somewhat more efficient so there is more excess ICE power available for charging. It behaves pretty differently than the PiP. The PiP typically stayed in HV when EV was depleted unless I went pretty slowly and it was charging just enough to keep the traction battery in the sweet spot. When EV is depleted in the Prime it toggles between HV (charging aggressively at 30-40mpg at 50 mph) and EV for fairly long distances, which my PiP didn't do. It seems to work out to better mpg in the Prime so far, but I haven't driven a ton of miles yet in HV.

 

The computer should be optimizing when ICE comes on optimize the ICE load so it operating in the ECO zone of the engine (rpm and load). Example, if the car is on a level road going below 30 there is not enough load moving to car plus change load to get into this ECO zone, so the car jumps into the EV mode.

Yes.
So the ICE has a RPM and Engine Load sweet spot range. ICE could be doing one of the following options:
1)Off (EV or Regen)
2)On- charging only
3)On-propelling car+charging
4)On-propelling car only
Assumptions:
A.)When the battery reaches 0 miles available, the car is going to act like regular gen 4 Prius using around the equivalent amount of battery as the regular gen 4 Prius.... It is going to use a limited amount of battery to do low speed/load EV work until this small reserve of battery is used up, then ICE will be forced on to recharge (a couple of miles maybe) even at low car loads. Anyway, limited EV is still available even when the car is forced out of EV or HV-EV modes on a low battery.
I expect to see option 4 at some speed, but...?

Yes, I believe the charging is more efficient, but not at the optimal times.

If I drive at constants speeds on flat land between 50 and 80mph, I should see at one of these speeds (or a range) where the engine load for "ICE only" is the most efficient way to drive the car (not ICE + charging). I have not seen that on long trips on I-95. It has always been ICE + changing and then some periods of EV (rinse and repeat). I still believe the EPA test scenarios are the driving factor for this.

Check this out.. How Vehicles Are Tested.

The biggest surprise is on the last page of the presentation. I think there is a big hole in my muffler.

 

Another consideration when comparing Prime behavior to the other Prii is that once the EV range is depleted, the Prime's battery still has more kWh left than a normal Prius. It amounts to having a lot bigger rubber band for storing energy with longer stretches of charging and of EV even when EV range has hit zero. Here are some SOC numbers, thanks to @john1701a:

So, 23% of 8.79 kWh is 2.02 kWh and 17% is 1.49 kWh. The Gen 2 (and, I presume, 3 & 4) has a 1.31 kWh battery which doesn't charge above 82%, which is 1.07 kWh. So the Prime has a lot more watt/hours to play with in HV mode.

 

Good numbers. Are we talking about 23%-17% = 6% HV operation. 6%x8.79= .53kWh for a lower limit and then maybe a equal 6% into the positive?? for a total of 2 x .53 = 1.06kwh which is almost the same??

 

Not sure.

With the regular Prius, the range is 38-82%, so 38% of 1.07 = 0.41 kWh. 82% is 0.88 kWh. The difference is 0.46 kWh. The Prime has about 0.53 in it's 17-23% window. So that's a little more.

But what I seem to see is that it must let it charge above 23% without it showing on the guess-o-meter. I may be mistaken about that, but it charges for a long time. I do know that if I switch to HV with something like 0.1 or 0.3 miles of EV left, and a warm engine, it will make that EV range disappear and keep on going in EV for maybe another mile or so and then charge it up to well above where it was when I went to HV. I seem to remember it going to over a mile of EV range after going HV at under 0.3 miles remaining range and then finally shutting of the ICE.

Basically, I'm still trying to wrap my head around it same as the rest of us. Whatever it's doing, it has impressed me.

 

Yes, around 100-82= 18% more for Prime.

 

I had forgotten that he mentioned that in there. Nice catch!

 

Based on the behavior I've observed so far, my guess would be that the larger number is more accurate. But my last car was the PiP, so I can't directly compare the Prime to a Gen 3 or 4 hatchback.