Ok, I need to know the real deal...I ran out of gas

I don't know.

I've put 50,000 miles on my 2005 Prius (as of last week). My average mpg is 46. I live in the foothills of the San Gabriels, so there's a fair bit of up and down here which probably makes more difference to the mpg than a little ethanol.

 

My 2005 apparently isn't as smart as yours. Unless I missed a button somewhere for that function.

 

True, it's only simple math to calculate the miles to empty, but it's not very useful on a Prius. Calculating the miles to empty number requires the computer to know the upcoming mileage. Should it use the current mileage, the best mileage so far this tank, the average mileage for the tank, average mileage over the life of the vehicle, or some other factor? There is no one correct answer. The Prius aggravates this by getting such good mileage. Even a small percentage change in mileage produces a lot off difference in the number of remaining miles. Let's look at an example: In the summer I average 57 mpg on our county roads. When I drive at highway speed I average 46 mpg. Assume I have four gallons of usable gas left in the tank. At my normal summer mileage, the miles to empty is 4 * 57 = 228 miles. If I pull onto the highway, my miles to empty is 4 * 46 = 184 miles. That's 44 miles difference, which is not an insignificant amount. If you use instantaneous mileage, the miles to empty will become infinite when on electric only. The whole calculation is misleading to the point where I suspect Toyota decided it was better to leave it off the display. I wouldn't mind having it, but I understand why it's not there.

Tom

 

Well here it is people, if I give any advice I'll leave it here and you can take my advice with it,
It is a grain of salt.

Because no matter how much I read about the Prius or how much time I spent in trade school or doing an apprenticeship, because my Prius hasn't got a bladder in the petrol tank I know precisely jack sh!t about them.

Thanks MacT66, I was blissfully unaware of this until you put me right.

 

FYI: There is a product that will allow you to see all the error codes in the computer and you can reset them yourself. I haven't used it, but have talked to some people that have, and its on my list of things to get for my Prius.

here it is: ScanGaugeII - Trip Computers + Digital Gauges + Scan Tool

:yo:

 

You are absolutely right about all of the reasons why it would be innaccurate. However, that has not stopped many car manufactures from putting it into their cars. I had an '03 Mitsubishi Montero that had it. It was pretty handy. When it dropped to around 50 miles left the readout turnned yellow, then at 20 miles left it turned red. It never got below 15, so I don't know what happens after that.

There are always reasons not to do something, but in the case of a "miles to empty" gauge, the reasons to have it outweigh the reasons not to have it. imho

 

Our 1994 Ford Aerostar has it, as well as a fully electronic instrument cluster. I like the feature too, although it makes more sense on the Aerostar. The mileage on that beast stays fairly constant when compared to the Prius.

As far as weighing reasons, you have to remember we are talking about Toyota. These are the same people that brought us the "press to agree" button on the NAV system, and the lock-outs on the audio, bluetooth, and NAV. That should be enough to tell you where they stand on the issue.

Tom

 

My commute is ~53 miles/day round trip, Escondido to Sorrento Valley, and I'm averaging 58+ MPG on every tank, winter or summer. In fact I had my best tank to date back in January (61.3). I also blocked the upper grill and it made a huge difference, even in Southern CA.

 

I have had tanks in the winter start off great this past winter during a mild warming up period and average 65MPG or higher through 200 + miles, then wake up the next morning to a week of 10 degree's with gusting winds and snow and all of a sudden it becomes a struggle to keep that tank avg above 50 MPG.

 

Sorry, but I think you are seriously misleading people. Yes, some NimH cells can be run down to 0 SOC for hundreds of cycles. However, they are not nearly as tolerant of this as their cousins the NiCd. NiCd were often stored at 0 SOC, as it was their preferential state. This is not true of NimH. Most prefer to be stored at some medium SOC, depending on design.

Even then, what is generally true for NimH cells doesn't necessarily have any bearing whatsoever on the cells in a Prius. The modules used were specially designed for use in hybrid vehicles in a collaborative effort between Toyota and Panasonic. The prismatic cells are optimized for very high specific power, discharge current (>20C!) and energy density, and for a very high number of shallow cycles. Toyota's controllers go to great length to keep these batteries operating in an optimal zone of SOC, charge/discharge current, temperature etc to maximize their life. When you run out of gas, you are no longer able to operate within those ideal requirements, because the electric motor becomes the sole source of power. It is forced to put out whatever you ask for. A single deep discharge under these circumstances could easily take thousands of cycles off the life of the battery pack. If it manages to go deep enough to reverse a cell it could kill the whole pack on the spot.

This was proven pretty effectively by several hobbyist EV conversions that hoped NimH modules from wrecked Priuses would be a cheap way to get NimH cells in their cars. In the end I don't think they even got close to 100 cycles out of the packs. Saying all NimH cells have the same properties regardless of their design is like saying there is no difference between a high end marine battery good for ~1000 full cycles and a walmart starter battery good for about 5. Both are lead acid batteries, but design and optimization makes all the difference. Likewise NimH like the Cobasys ones used in the EV1 or the Panasonics in the RAV4EV have shown incredible cycle life, but only had about 1/5 the specific power of the Prius modules!

There are several safe guards against doing this kind of damage, but all of them can be ignored by the driver. First the car tells you to "Add Fuel". If you ignore this and run out of gas, the car throws multiple warning lights including the master warning which mean pull over and shut the car off now! If you ignore this and keep driving, the car will shut down the hybrid system when you get down around two bars, hopefully before any serious damage is done. If you restart the car and keep trying to drive, you are probably doing damage to your battery. In addition you are potentially putting the entire HV system under strains it was not designed for in terms of duty cycle and temperature. The car assumes that the only reason you would ignore all these warnings and keep trying to drive the car was if you have a very good reason, and lets you do so.

It is exactly this case that we are trying to caution people against. Unless your life is in danger, you should pull over an out of gas Prius and call a tow truck. A number of people have not done this, and several have damaged their batteries as a result. Since the effects are often delayed, as you are taking cycles off the end of the battery's life, we'll have to wait and see how common this ends up being. Personally I'd rather not be one of those guinea pigs, when the prize is a bill for several thousand dollars and a denied warranty claim.

Rob

 

Sub-dude (subdued?),
Thanks for the info. By the way, with what did you block the upper grille?

 

You're right, I am overgeneralizing. However the Prius does try protect the battery from cell reversals, so you'd have to be pretty stupidly persistent to get that to happen.

My initial response was to the claim that running the battery to the point that the Prius stops (without retrying) causes horrible and irreparable damage to the battery. Or even significant damage. I don't believe that it could.

For those that have already run out of gas (hasn't happened to me yet), and kept driving the Prius for a little ways, my contention is that the sky hasn't fallen, as others on this forum were claiming, so don't sweat it. Just don't let it happen again.

I will retract my claim that dozens of such instances won't significantly impact the Prius battery life, since I was generalizing that from typical NiMH experience. As you point out, these batteries are obviously more sensitive if they fail after cycling 100 times.

I would like to hear the details of these examples. What exactly did they do, and what happened to the HV battery as a result? It must have been more than simply failing to stop when they were out of gas.

 

Well, thats the real question. People seem to be a little sheepish with the details when they realize it may be their own fault their battery is dead. Combined with the time delay of months or more, accurate details have been hard to get. I think you are right, by far the greatest danger to the battery is those who continue to try and restart it and drive it after it dies the first time. Toyota has also been pretty vague on exactly what circumstances will cause them to invalidate the warranty, or what specific data they can retrieve from the car to prove you ran the battery too low. I do not doubt that the data exists, we know of a number of recorded parameters than can be used to show abuse, but I would like to think they can differentiate between someone who just ran out and pulled over vs. someone who tried to push it. My guess is that since the hybrid shutdown is probably a recognizable event to the controller, it would also be able to log an attempt to restart without refueling after this has occurred. What we do know is that Toyota has already invalidated the warranty of at least one member with a dead battery because of this issue. As I recall this was an '05 with ~70k miles and he did try to restart after it died completely the first time.

You are right, the controller keeps the battery on a very tight leash to protect it. The problem, as I understand it is that this all goes out the window when you are in an out of gas condition. The car assumes that if you ask for power you must be in an emergency and need it. I believe the car will ignore its own current limits (CCL/CDL) which are normally generated dynamically based on temperature, voltage, SOC etc, and just give you what you ask for. This could create situations where the battery can be damaged even before the shutdown occurs. The hybrid system shutdown that occurs somewhere around 1-2 bars is its last ditch effort to protect itself and leave enough juice in the battery to start the ICE. If you restart again and keep driving then all bets are off. If the controller is off duty, I think its really not hard to reverse a cell. We're talking about a series of 168 cells, and NimH are pretty famous for not being very well balanced. Add to that the high current (up to 150A) and fairly high resistance of the cells and its a recipe for problems.

The PHEV conversion folks are toying with the idea of simulating an out of gas condition to allow you to break the 34mph EV barrier. In this situation the risk is reduced as the plugin pack is supplying 70-90% of the drive current, and the temperatures of the inverter and motors and SOC of the primary pack can be carefully monitored. Even under these circumstances there seems to be a lot of debate about how safe this is to do within that community.

We are over simplifying the situation by saying don't ever run out of gas or you'll kill your car and have to pay for it. The reality is probably closer to this:
1. Try really hard not to run out of gas. If your last pip flashes fill up asap.
2. If you run out of gas, coast to the side of the road and stop where safe.
3. If you are unable to get to a safe location, or can see the gas station you may choose to go for it. Drive as gently and slowly as you safely can. Avoid hills! Turn off all uneeded accessories to conserve power. Watch your battery meter and don't run it down too low. (Maybe above 2 bars is ok?) Be aware that there is a small chance you are damaging your car.
4. Anything beyond this risks serious damage to the car. If its an emergency, you may decide to go for it and deal with whatever consequences may arise.

On the other hand, I don't want to be held responsible when someone follows the above and then still manages to mess up their car. Its much easier to just say "Don't run out of gas! If you do, pull over and call a tow truck!"

Rob

 

thanks to bill wilson for the most informative, sensible, question answering post i've seen here yet.
i want range. the 11.9 should convert to minimum 540 miles if i avg 45mpg. at first that was the case, and i was filling up with 10 + gals. since i ran out of gas it wont take more than 9 gals, even when it's blinking.
my question now is-how do i get it to fill up to max capacity again? i'm getting ready for a 5 to 6,000 mi trip and i want to go-non stop for at least 500 miles.
my Camry got 31 mpg with a 15.9 tank and that's what i want-range.

it ain't sexy to me, just the way i like to drive.
please, no moralizing, tsk-tsking or self-righteous finger pointing. Just how do i get the thing to take the full capacity?
thanks.

 

Another, probably obvious point about batteries: You can hurt them without killing them. This isn't a black and white issue. You can take the HV battery way down and still have enough juice left to start the ICE. Does that make it good for the battery? Not necessarily. The HV battery on the Prius is normally cycled through a very gentle range. Taking it through a deep discharge can take a lot of life out of it, even if you don't kill it on the spot. It's like asking "How long can I run my engine without oil?" You can get away with it for a bit, but it's not going to do any good.

Tom

 

The manual also says "The fuel tank capacity is decreased at low ambient temperature. (decreased by about 5L (1.3 gal., 1.1 imp.gal.) at -10 degrees C (14 degrees F).)

 

Carry a 1 gallon spare can. The small plastic ones work great if you keep them out of direct sunlight, heat and don't spill gas on the outside after filling. Enclosing them in a second, garbage bag can also help but the best approach is to minimize exposure to heat and don't spill any gas on the outside.

GOOD LUCK!
Bob Wilson

 

Apart from a suggestion to light a small fire under the fuel tank to warm the bladder I can't add any more because of the restrictions above.

Of course I have a Prius without a bladder in the fuel tank so I am not even permitted to say anything about the Prius or any of its systems.

Sorry.

 

Anybody ever though of an electric heater for the fuel tank? Just something that keeps it at a constant temperature where it takes the full 11.9 gallons? Now that would be a cool add-on for the Prius, warm your bladder on the way to the gas station so it fills up to its max...!

 

OH Pat some of us enjoy your many contributions to this site and don't care if you have a bladder or not in your Prius. Where is the love why don't you put MacT66 on your Christmas shopping list ... I even have a great gift idea for you to give MacT:

<IMG style="MAX-WIDTH: 800px; ; WIDTH: expression(this.width > 800 ? 800: true)" alt="" src="http://www.dreamproductscatalog.com/images/products/detail/94753.jpg" border=0>
and here is where you order it: Google Image Result for http://www.dreamproductscatalog.com/images/products/detail/94753.jpg