EV Mode: Why I'm Lovin' it!

Hmmm, interesting method...will try tomorrow! Thanks.

 

I've been doing the same in my GenII the past couple weeks. Seems to help FE.

 

i was using this method in my GenII while delivering for Cookies By Design... i was averaging about 50mpg.. up a good 8mpg from what i usually averaged.

 

interesting. Maybe I shall experiment. Thanks for sharing.

 

When ever I try doing that my Prius disengages from EV mode at around 11mph. It beeps at me and the screen says EV mode disengaged due to excessive speed. I don't know if I'm doing something wrong or could the software in my car be different?

 

Thanks for sharing.

 

When I first read this, I was thinking no way. But I am able to exceed the middle line on the HSI without the ICE kicking in (speed below 25-26). So yeah, I am able to make it between lights downtown w/o ICE until my battery gets too low.
Thanks for the tip.

 

It would be nice if it was possible, but this would contradict the laws of physics, and everybody knows they don’t like to argue.

First, one thing to keep in mind: In a non modified Prius (ie with more batteries that can be charged from the grid), the only energy source is gas. Every time you use battery energy, you need to charge it back later with energy from gas. There is no such things as perpetual movement of free energy.

What you’re suggesting is that it would be more efficient to:


1. Use EV mode to accelerate:

• Convert chemical energy in the battery to electrical energy (some energy is lost*).
• With the inverter, switch/change the voltage/phase of this electrical energy to what is required to drive the motor (some energy is lost).
• Convert electrical energy from the inverter to mechanical energy with the motor (some energy is lost).
• The car moves.
• As you have depleted part of the battery energy doing so, you will soon or later need to:
• Run the ICE to convert chemical energy (the gas) to heat/pressure in the cylinders.
• The pressure is then converted to mechanical energy (some energy is lost).
• Convert the mechanical energy to electricity by using a generator (some energy is lost).
• Convert electricity to chemical energy in the battery (some energy is lost).

2. Than to use normal/ECO mode to accelerate:

• Run the ICE to convert chemical energy (the gas) to heat/pressure in the cylinders.
• The pressure is then converted to mechanical energy (some energy is lost).
• The car moves.

*energy is not really “lost” but simply converted to heat, which serves no purpose to move the car.

The only time when moving the car with the motor instead of the ICE is more efficient happens when the ICE is inefficient to do so. In a simplified manner, one could say that this happens normally when the car turns the ICE off by itself (while stopped, gliding, etc.).

As stated in the manual, EV mode will almost always lead to a decrease in fuel economy (MPG).

But yes, it is still cool to use to impress people, but not to reduce your fuel consumption.


PS. This is a simplified version that is not completely accurate but still depicts a good comparison between the two options.

 

I have 5 stoplights before I hit the freeway so I'm going to try it. Boring physics aside, I'll recharge the battery on the rest of my 40 mile trip to home every day.

 

And of course the gas used to refill back up the battery will be free!

 

When the engine is cold, it will get out of EV mode at a lower speed or when your acceleration is too brisk. Once warmed up, you will be to achieve higher speed and it will stay on EV until you reach the PWR part of the HSI.

 

Can't let the ICE work for forward motion alone.Kill 2 birds with one stone

 

converting ice power to electrical power tends to be more efficient than using mechanical energy to spin the wheels.

using electrical power for the most inefficient parts of acceleration is more efficient than using ICE power alone for those purposes.

cruising like normal above 25 mph with little regenerating taking place refills the battery a bit and lets you continue. there is a gentle balance where you can drain the battery.. it just takes time and effort to know how to get around that.

you guys love to argue losses in small percentages in conversions.. the real fact is that it's been tested and works. i've used this method and averaged higher than normal.. therefore something works in the theory.

think outside the box for once in your lives.

 

I've been doing this recently and it does seem to help. I don't think anyone is claiming to have built a perpetual motion machine. The efficiency mix of the battery+motor vs the ICE is still somewhat a free parameter. The prius software tries to perform an optimization but you can game this system with the accelerator and somewhat impose your own optimization. Also the prius software does not know what the next x miles of your drive is going to look like so it can't predict the best time to expend electrical energy and when the best time is to charge. I think there is some merit to the operator taking on some of these optimization tasks. For example, I think the EV mode acceleration works for me because there are plenty of other inefficient parts of my commute, especially steep hills, where the ICE is running (and not efficiently) and the additional load of charging the traction battery doesn't matter much. I think one of the biggest points to having the (little) traction battery is to smooth out the inefficient parts of your drive (acceleration and braking) where you can acquire the electrical energy without much penalty, and use it to improve the efficiency during other parts of your drive. There is no reason that you can't decide yourself when to use the stored electrical energy. However, I believe you (and the manual) that you can easily make the overall efficiency worse (but not always!).

 

My recent real life experience points to the contrary.

After learning and understanding the Gen III Stages, I’ve started to let the engine warm up for 30-50 sec before getting out of the driveway, to avoid driving the first 2-3 km on the battery only (stage 1a). I first thought it would impair my fuel economy (letting the ICE run “for nothing”), but to the contrary, I gained few decimals in L/100km (around 56 to 59 MPG) on a short commute (less than 10 miles).

This lead me to confirm that using driving in EV-mode is generally a bad idea.

I'll have to try this... (in an open-minded way).

 

I was thinking about motor/generator efficiency mentioned in this thread. Resistance in electrical circuits is the problem. So what ever happened to super conductors? As used in the Large Hadron Collider but when will the be used in the Prius?

 

I certainly think that there are places to use EV to gain mileage. For me, I live at the top of a 1/2 mile hill (all in a 25mph neighborhood). In standard mode, the engine will not hold 25mph without the ICE on my street (especially considering speeding up to 25 after the stop sign at the bottom). At the end of my 18mi commute I use EV up the hill and drain the battery. Then in the morning, I use low throttle pressure to leave the house and go down the hill. Then I have a longer hill and faster conditions where I must use the ICE. This works to re-charge the battery for the rest of the trip. This simple change has netted me around an extra .5 mpg. Not bad.

 

All you will need is high temperature superconductivity. All things being relative, high in this case mean more than 30°K, or even above 77°K (> -321°F), as you could cool down your motors/generators and such simply with liquid nitrogen...

In the case of the LHC, it uses liquid helium @ 2°K.

More seriously: In this domain, the holly grail would be to achieve superconductivity at room temp.

 

A .5 MPG difference on what MPG value? By itself, it is meaningless.

MPG being what they are (1 / fuel consumption), the fuel saved by a .5 MPG difference is not constant over the MPG range.

For example, a 0.5 MPG difference between 10 MPG (100 Gallons per 1000 miles or GPKM) and 10.5 MPG (95 GPKM) corresponds to a 5 GPKM difference (1L/100km), while the difference between 50 MPG (20 GPKM) and 50.5 MPG (19.8 GPKM) is only 0.2 GPKM (0.04 L/100km). Over a 1000miles distance, in one case you save 5 gal, in the latter, you save 0.2 gal.

That's why making a 20 MPG SUV move toward 30 MPG has a lot more impact than having a hybrid go from 50 MPG to 60 MPG. In fact, in this exemple, you would need 5 improved hybrids to save the same fuel as one improved SUV.


http://nudges.wordpress.com/why-we-misunderstand-what-miles-per-gallon-ratings-are-telling-us/