can't always creep around on battery-why?

Depends on many many factors. State of Charge (SOC) is a big one, battery temperature is another big one. Then of course the engine temperature is factored in.

Can't really say why, since not enough information is given on the variables. Without a device hooked up to the CAN bus sniffing internal data, you won't be 100% certain when EV glide or EV mode is available.

And just so you know, driving in forced electric will lower your average MPG.

 

How do you charge your battery? Via gas. You can read about it on this forum or just think about the physics for a bit. No energy conversion is 100% efficient. Going from gasoline to kinetic energy to spin the electric motors as generators into electricity then store into the battery, then out of the battery into the electric motors and to the wheels is not as efficient as gasoline to kinetic to wheels.

 

it will go up as you're driving ev, but will go way down when the ice comes on to recharge the battery.

 

I wouldn't say will, more like can. I would still do the majority of accelerating on gas.

Is it usually not doing EV when you're coming back from somewhere close or does distance seem to not matter? If the car hasn't entered stage 4 (full hybrid mode). To do so you need to come to a complete stop with the ICE warmed up and running. The engine will continue to run for 5-10 seconds before shutting down. Then you're in full hybrid mode. Don't ask me why Toyota made it this way, it makes no sense to me.

Using EV mode isn't free. Its free for the moment, but that energy from the battery needs to be replaced eventually, and the Prius ultimately gets all its energy from gas. It can be advantageous to use it, but mainly at speeds under 20MPH. I would just pulse and glide for anything faster.

 

People seem to forget the "Synergy" in Hybrid Synergy Drive.

The greatest overall efficiency comes from the synergy or blending of electric and gas. The Prius IMO is not at it's best in the rare occasions of either full electric, or full ICE.

Going on full electric for a distance can be "fun" and certainly may up your gas mileage for that specific trip, but as pointed out, sooner or later you MUST recharge that battery.

It's the tanks average that really matters. I can coax a great single trip MPG sometimes if I'm paying way too much attention to whether I'm in EV mode or the engine is running. But my tank average at the end is going to end up being pretty much the same.

Seems to me, that for the "average joe", The Prius operates better in the "middle way". That is with a battery not too low, not too high, and being driven smoothly and efficiently, but letting the computer blend the power. In this manner I consistently get great gas mileage almost all the time, and not the hills and valley of MPG statistics created by coaxing every last drop of EV out of a battery charge and then having the engine work double hard to keep me moving AND recharge the battery.

 

This neglects the energy put into the battery by the regeneration systems. Contrary to what is constantly stated in the various forums, there is essentially no cost associated with the regen energy. The physics is not necessarily intuitive, but consider that you burn 10 cents worth of gas and then regenerate one cent back into the battery. Do you subtract the one cent from the 10? This would mean that you really only burned 9 cents of gas...this is clearly not a good argument. The only other choice is that you get 11 cents of energy for 10 cents, which is what thermodynamics also says, and is one of the main reason the Prius gets such good gas mileage. On the highway, where regeneration is harder to come by, the situation is different and it shows up in the decreased gas mileages at high speed.

 

While the observations are true, the conclusion you draw is false. Yes regeneration is a net gain for fuel economy because you are recapturing the same energy you already burned as gasoline. But it is extremely inefficient. In the neighbourhood of 10% or so. Regeneration is nifty, great for brake wear, and does increase fuel economy. But that is NOT what makes a Prius get good fuel economy.

There are very very few times that EV driving will net you higher average MPGs. Lots of times it will hyperinflate the short term average, but in the tank-by-tank (or bladder-by-bladder) average it will most of the time be a net loss.

Examples where it is useful include using it before stretches of long regeneration that would otherwise fill the battery, or using it for periods before the engine will be on constantly at higher RPMs like higher speed highway driving.

Scenario A I use often because I live on a mountain. From my driveway to the main road up the "hill" is a short stint uphill. I do this in EV. I then regenerate down to the bottom of the hill completely filling the battery. This is all energy reclaimed by the same gas that took me up that hill previously, stored as potential. If I am going for a long drive I let the ICE warmup on the way down the mountain. It does no work and is therefore allowed in its most efficient burn cycle for warmup (which by definition is inefficient).
If I am just going to the store across the street from the bottom of the hill, I keep it in EV to the store because warmup of the ICE would be wasted.

Scenario B can be used when manoeuvring from a parking lot to an interstate onramp, do your warmup on the highway.

However, most people use EV mode as the OP to creep around neighbourhoods and such just because they can. And in this case it will lower your average fuel economy as proven many many times.

Having said that, I creep around in EV while in parking lots. It lowers my fuel economy, but I find it somewhat entertaining, I don't know why. The fraction of a penny it costs me in gas is worth the small smile in my face when I spook some idiot on a cell phone zombie walking.

 

I did not discuss using EV mode in my post. I am assuming you mean the push-the-EV-button mode. I do not remember the last time I did that. You can run in EV and let the Synergy systems do the work without using the button to override the firmware. You are incorrect in your statement concerning the regeneration contribution to the fuel efficiency of the Prius. Toyota engineering attributes 30% of the fuel efficiency to the regen systems, 30% to the Synergy firmware, 15% to the engine with the rest due to aerodynamics, etc. This is one of the main reasons your mileage drops on the freeway- there are fewer opportunities to regenerate energy. If by the 10% efficiency you mean you only get back 10% of the gas cost as reclaimed energy, then I would agree that is probably in the ball park.

 

You can't force it into EV node whenever you want, but you can request it. The only difference in requesting it versus letting the car decide when is that you can bypass the warmup cycle if requested within the first 7 seconds of startup before the ICE starts warming up. Of course battery temperature and state of charge still matter.

To request you press the EV button. In non North American Prii, yes Gen2, there is a stock button. For the North American market they took away the button but left the programming. So to activate you need to ground pin 26 (?), going from memory here, of the HV ECU under the glove box area.

 

Lots of peeps think regen is bonus $$$.

Anything that slows the car down costs gas to get back up to speed. The negative consequences of Regen are removed when you are at speed. Then momentum helps you.

Anytime the car runs on EV it costs gas to charge the Hybrid Battery back up.

Only time you should run on EV is if the Hybrid Battery is in 7 bars Green. Then you have a tiny amount of extra battery energy to burn and it won't turn the engine on till it hits blue bars. Won't last long. Enjoy it.

This car runs on gas. I swear to god.

 

This is a common, but incorrect, assessment. If you use 10 cents of gasoline energy to get to 35mph then regenerate one cent into the battery, you have 11 cents of energy but only paid 10 cents for it. Seems pretty free to me...and to the 2nd law of thermodynamics. You are trying to connect events that cannot be causally linked. The point is that you HAVE to slow down from time to time...at least I know I do. If you are accelerating then regenning just to charge the battery your analysis would be correct. Even when the engine is charging the battery, the Synergy firmware does it using the most efficient energy it can. I agree that using the EV button is not normally a good idea. There might be some circumstances that would benefit from it....you really don't need it anyway since going into a glide will put you into EV.

 

Hmmm. I will say this much. Gliding is NOT the same thing as EV.

When you glide, no power is being used other than inertia. When you are EV'ing you are actually using power from the traction battery to power the electric motors to propel the Prius. I believe you are confusing the EV mode and gliding which is part of what is known as hypermiling.

The beauty of the Prius, especially the first and second generation is the fact that one can glide easily once one learns the techniques of hypermiling and the ICE is in stage S4. A true glide is only when there is NO power going from the battery to the drive wheels and or NOT returning (regen) from the drive wheels.



I post this to clarify what the above post implied to the average reader here on Prius Chat.

 

I hear you Edthefox5, but I've always thought of Regen mode as a fantastic bonus technology on the Prius II. I have programmed my brain to always make use of Regen when I'm behind the wheel. Going down several steep slopes while commuting ensures that energy I would have inevitably lost in some ordinary automobiles is skilfully recovered and stored for me to use later - while also helping to slow the car down very smoothly. It doesn't matter how much energy is recovered, every little helps, especially when using Electronic Climate Control - albeit on its least setting. I love working with the car, using EV mode (without invoking it with the button) wherever prudent and possible, and when the ICE has to kick in, I take pleasure in the fact that even while the ICE provides traction, it also engages in charging up the HV Battery too. The system works!

I've never bothered with using the EV button. As far as I'm concerned, there's no need. I get to decide when to use EV on stretches of road when I have enough battery power and I'm happy to let the onboard computers back up my decision or otherwise override my intentions and invoke the ICE. Yes, you're right. This hybrid's primary power source is still Petrol, but do I really enjoy the capabilities of the Hybrid Synergy Drive.......this car might as well be a UFO

 

I guess I have redefined glide in my own head since you can use the battery during glide up to the point the power bar crosses the midpoint. This was a lot more difficult with my GenII. I do not mean to confuse anyone. It is confusing enough with two EV modes.

 

You have to remember that the Gen II and the Gen I are completely different from your Gen III. The displays are not the same, nor is the technique used for hypermiling. It is similar, but one has to learn how to use the different read outs (displays) in the various generations.

 

Still not understanding. It costs money to repeat this. Its not a bank.

10 cents to get up to 35 mph's. Then since your not going fast you generate 1 cent regen when you are forced to stop. Now since your stopped you get to spend another 10 cents minus the 1 cent from regen to get back up to 35 mph's. That 9 cents (EACH TIME YOU TAKE OFF) either comes from gas to the engine or Hybrid battery power. And it cost's more than that 1 cent to keep that battery charged.

Regen in low speed around town stop & go contributes very little energy. Most of the charging energy comes from the engine turning MG1. Which is why the mpg's are very poor in stop and go.

On the highway different deal. You harvest alot more energy in regen becasue of the wheel=gen speed and lose little momentum to get the car back up to speed unless full stopping. So regen is your friend there.