Regeneration query

Hi Mark,

The PiP has two limits that play into this question:

1. is the maximum power that the battery can take (itself IIRC dependent on SOC)
2. is the available battery capacity.

I don't have a PiP, so I may be remembering wrong that max power is 30 kW, and nominal capacity is 4.4 kWh. The capacity as a practical matter of course depends how full the battery is when the descent starts.

800 feet is about 250 meters, and since potential energy is m*h*g (in joules), that drop is about 1600*250*10 = 4000000 joules = 1.1 kWh. Somewhere around 400 Wh is used for two miles of flat road, leaving ~ 700 Wh. Regen is about 50% efficient, so about 350 Wh of battery capacity 'space' is needed.

As for power, so long as regen is kept below maximum on the display that will not come into play. Another way to figure this is to look at the elevation drop/second. Lets say the car speed is 60 mph = 27 m/s. Over the shorter course of two miles, the car drops 800 ft/120 seconds = 2 m/sec, equal to 32 kW (using m*g*h/sec). No problem, since conversion efficiency is around 50%.

Addendum: The Toyota spec says 38 kW max power for the traction battery in EV mode.

 

You have some good points but probably should belong in a different forum. In quick, any change should be gradual. Changing to $7 won't necessarily be the answer either. I wonder if you would have been anti-Prius from the beginning also when sales were dismal and there were incentives? Maybe you don't like Prius? Either way, maybe create a politics of hybrid/ev driving thread

 

Not my experience. I do set my temp to lowest setting.
Est. EV at end of charge 10.1
Start descent est. EV 10
Turn on fan no AC est. EV drops to 8.7
At bottom hill est. EV 9.1
Turn off fan est. EV jumps to 10.3

 

Thanks for your comment. I'm a capitalist so I'm not anti-prius or any particular product. I'm more anti-government using tax dollars to do stupid things that don't work. A lot of Prius owners that I met are not really interested in saving the planet. They are more concern about how little gas they user per mile. For years, I drove an SUV and I was greener than my friends who drove a Prius. I was working from home and lived closed to work. I only put on about 5000 miles on the SUV per year. Meanwhile, my friend put 30k mile on his Prius and he goes on two cruises per year with his wife. I don't think I need to tell you how much fossil fuel those cruise ships burn and he and his wife had to fly to the ports. Those jumbo jets are not fuel efficient either.

Another thing that pissed me off was that some states let Prius driver get on the HOV lanes. Driving a Prius alone in your car does not reduce traffic congestion. People who carpool are the only ones should be rewarded with HOV lanes because they are the ones who are trying to reduce traffic congestion and traffic congestion is one of the reasons why we burn a lot more fossil fuel than needed to.

To make a long story short, to save this planet, people need to change their behavior and the government should either reward good behavior or punish bad behavior. Promoting a product via rebates is a waste of tax money and it doesn't work if you decide to look at the forest, instead of just a tree. One easy way to change people's behavior is start taxing gasoline heavily. But I do agree with you, it has to be done slowly.

 

Are you exceeding 62 mph ?

 

Why are you so concerned about the EV light? As long as you're regenerating without the ICE coming on, that's what you wanted, right?

 

I don't know why the EV light turned off. It might be informative to watch the energy flow screen to see if the ICE is consuming fuel. A regular Prius is kicked out of 'EV mode' at 34 mph IIRC, but I thought the PiP has a much higher speed threshold of 62 mph.

A SGII or Torque (android) OBD2 car network sniffer would immediately tell you if the ICE is spinning.

Addendum: Perhaps you are in HV rather than EV mode ? Look at page #60 in the user manual.

 

As long as just the EV icon is still the one on the screen, you are still in EV mode whether it is lit or not (outline is still there). I have had that happen to me as well. As soon as I call for power the icon lights up again. If it goes over to theEV/HV screen then the ICE would fire up as far as I know. If you are still adding regen and see more EV milage you should still be OK.

My 2¢ anyway.....

 

Don't confuse the dedicated green "EV Mode" light on the left of the dashboard console, with the "EV" car icon over the HSI display.

If it is in "EV mode", there is only the one car icon over the HSI dispaly, and if it is filled in with "EV", then then ICE is not running. If it is just an empty outline, then you are still in EV mode but the ICE is also running.

If the "EV mode" light is off, then there are two icons over the HSI display, one a smaller car, and if the car icon is filled in with "EV" , then the ICE is not running; if empty, then the ICE is running.

 

If you have the single large icon of the car with the letters EV in it, then you are in pure EV mode and the ICE is off. If you have just the outline of the car, you are no longer in pure EV mode and the ICE is spinning and consuming a small amount of gas. Short of putting the car in neutral, there is no way for you to start at the top of a 2-mile hill with a fully charged battery and not have the ICE come on at some point. Fan use won't have a significant impact on preventing the ICE from spinning. The A/C system pulls a max of about 900W (fan on high, temp set to lowest). Just coasting down a hill will generate 2 to 3 times that amount. Any braking, and you are easily doing 10 times that amount. Turning the fan on doesn't magically make the battery have more charging headroom, it just reduces the estimated amount of EV miles available.

 

I stand corrected! should have known that... Actually I think I did... Brain Phart when I'm not in the car.

 

B gear will make more brake resistance than D gear. B gear simulates downshifting to a lower gear. D gear (foot off pedal) simulates torque converter drag.

In a regular Prius, B gear will start the ICE before reaching the limit NiMh can recharge. That's throwing away partial energy that you could regen with brakes in D gear.

In a PiP, the bigger PHV pack can absorb enough downshift resistance without starting the ICE at any speed in EV mode (below 62 mph).

Many don't get this so let me put it in numbers. Say D gear creates 10 kW and B gear 30 kW max resistance. A regular Prius will start the ICE if B gear request more than 15 kW. That happens if you drop it into B over 25 mph. ICE may Jake brake 10+ kW and battery regen 5 kW. If you regen brake in D gear, NiMh can absorb up to 27 kW.

PiP lithium battery can absorb 38 kW so B gear can't max it out.

To answer OP question, it depends on the traffic of each route. Take the path with less sudden stops. If they both are the same, take the longer route as it will regen at slower rate. It is better for the battery life. The energy recaptured should be about the same.