Stealth Mode

There are many many threads on the subject. Look around. This is a good start if a bit dated: http://priuschat.com/forums/kb.php?mode=article&k=14. A few hints. With out a EV switch the engine needs to be warmed up and at optimal temperatures. You are not going to have any luck prior to that. There are two levels of stealth. The easier one is when you are looking at the Energy display going below 41 mph take your foot off the gas and you will see arrows to the battery indicating charging. Let that go for 2 or three seconds. Now very gently like there was an raw egg between your foot and the gas apply pressure. Don't brake the egg! As you press the arrow to the battery will disappear and you will see a arrow from the battery to the electric motor (MG2) and then the wheels. The engine (ICE) is off during all of this and has been since you took your foot off the gas. This is called feathering the gas. The next level is what is called "gliding" When you are going into stealth that there will be a moment when there is no flow of power in any direction too or from the battery, motor (MG2) or the engine (ICE). No apparent power transfer. It takes very light feathering on the gas to get there. The other time you can go into stealth is at low speeds in a parking lot. With the ICE warmed up, gentle pressure on the gas will allow the car to go into electric mode with the ICE off. Search for feathering, stealth, pulse and glide.

 

I am a newbie somewhat myself, having just achieved the first 1000 miles. I am getting a consistent 51-53 MPG on my daily commute of 85 miles roundtrip. The secret of Stealth Mode Nirvana seems to be a light throttle foot. On a level stretch of road, slowly back off the accelerator while you watch the arrows on the energy screen. When the orange arrows drop out showing ICE is off and the blue regen arrows appear, then gently apply pressure back to the throttle where the yellow arrows appear, showing power flow from battery only to the drive motor. Voila!

If you have to accelerate a bit harder to stay with traffic, or you hit a small upgrade, the ICE will come back on, and you drop out of EV mode. I have gotten sustained speeds of 35 to 37 mph in Stealth, its great!!! Once you get past 45 mph, it seems very difficult to run in EV mode, the ICE wants to be on. The experts here in PC probably know all the software laws that control when EV can be on, whereas I am empirically discovering them as I go.

PS- the other advantage of a FADEC control on your car is that the cruise control will hold speed dead nuts to what you set, with virtually no drift up or down with road conditions, based on what I see so far.

Don't forget to get those tire pressures up, per the recommendations here in the forums.

Enjoy!

Infidel

 

42 mph is the majic speed limit to running in steath powered by battery. You can be going faster and let off the gas and then engine will appear to shut off, but its probrably freespinning. Sometimes the engine will be stubborn and not want to run stealth even though it appears to be warmed up... but that may be because you have alot of heat or A/C function going, or the batt needs charged.

Many times while cruising under 42.. the easiest way to test to see if stealth will run is to simple let completely off the gas until you see the ICE stop, then barely give it gas until you see power coming only from the battery to the wheels.

I am installing the Coastal EV mod tommorrow.. but its not necessary once you get the hang of it... but it will make it much easier and ensure it won't bounce back and forth until your ready or the battery gets down to about 3 bars, or you punch it.

 

Using a longer route will get you past the low MPG of the ICE warmup and spend more time in high mileage mode than the more direct route. On the other hand you will use more gas per trip, just because of the extra distance. Unless there is a drastic difference in the terrain and speeds, you will use about the same amount of gas in the in the distance of the more direct route with the longer route. From there on the extra gas used will really be a waste. Are the braggingr rights worth it?

 

Plus I never like the idea of getting to my destination with a battery with only 2 or 3 bars and then leave it that way for too long.

I don't have definitive research that says its bad and I know you can leave AA NiMH batts low without harm, but since we have so many cells hooked together to get the 201.6 volts, its good to keep them up more so they are all equal. I've also heard of danger of cells reversing polarity and such if they got toooooo low.

The EV mode will never let them get that low, but if you let it sit for days after running it low it could. NiMH lose 2 - 5% a day just sitting.

 

I don't think this is true. Toyota where paranoid about the battery longevity for the Prius. The battery scale you see on the display is not linear and not accurate. When it reads low your batteries are still at like 60% full, but the prius will not let you go below that.

So I don't see how leaving the batteries low is a bad thing. I actiually intentionally do so here when it's cold. I try to end up with 3-4 on the bar as I know the engine will run for some time in the morning and I rather use that to recharge my batteries then just wasting it.

So I try to run EV mode as much as I can towards the end of my trip, then I let my Prius stay overnight and in the cold morning the engine running (to warm up) will recharge them to 6 or so. Then I use some of that when I get close to work (tend to end at 4 or so) as I know the Prius will still run a little in the afternoon when warming up.

It's my way to try to catch as much of the engine runnning (when I can't control it) into the batteries.

Note that when the ICE is running I try to use it as much as possible to propell the car forward but with city traffic Iunfortunatley can't do that 100%.

 

On a healthy battery it may be ok..
Also since NiHH has a sucky shelf life and lose 2 - 5% a day just sitting there. If you brought the voltage down really far and then let it sit for long.. there would be even more danger that the weakest cell could drop low enough to even reverse polarity if it reached zero volts.
This is what I've read.. however I don't completely understand it, but since the weak cell is connected on both poles by another cell, that means the + pole is connected to a negative pole of its neighboring cell, and the negative pole of that same cell is connected with a + pole on its neighboring cell. So concievably if the cell got weak enough it would reverse polarity and take on the voltages of its neighboring cells on both sides thus effectively reversing polarity.

Once that happens the total volts of the battery "201.6" would drops in volts since it just effectively lost a cell.

we have a concurrent thread running about this too:
http://priuschat.com/index.php?showtopic=1...=0&#entry207149

 

I hadn't heard that the NiMH batteries lost charge that fast! Seems a little to much too be true! So a car parked 20 days could go from a full battery to completly empty. Does't make sense. I will look at the other thread.

 

Newer NiMH, including those in the Prius, don't lose charge that fast. Battery longeveity was a major concern in the design of this car, a large safety margin has been established. Normal operation won't stress your battery. Leaving your car for unusually long periods, like greater than 6 mos, or running out of gas and driving the battery all the way down, may cause stress. But plenty of people have even done those things and still had a fully functioning battery.

 

That makes sense to me, but do we have anyone with history that has used the EV mode for several years and still feels like they have a healthy battery?

I don't know if the older classics would do EV mode would they?

 

Good question. But the EV mode is sold in Europe (I think) and in Japan and we haven't heard a lot of complaints from them. I suspect it was fear of litigation more then anything else that didn't bring that feature here... But that's just a theory.

Anyway. I would probably drive in the EV mode under the assumption that Toyota had thought about this problem. It seems like EV mode gets cancelled for low battery (just like you can't force EV mode through feathering if you have a low battery)

 

I agree..we are sue happy.... and since we are not warmed up to the idea of hybrid.. they may be giving us a better warranty on the battery?..
that would be interesting to know....

It seems the car is actually built for it.. I heard the earlier classics were not since the battery was smaller.