Losing power from MG2???

[font=Comic Sans MS:4e89ce276d]I have no constructive comments, but I'm interested in what you learn from the dealer. Goood luck, I hope it's nothing serious.[/font:4e89ce276d]

 

I am experiencing the same problem. It seems to happen randomly whether or not my Prius sits out in the sun or not. I took it down to Power Toyota in Tempe for them to look at. They basically handed the car back to me and said that there was nothing that they could do since there were no codes in the ECU. They have put me in contact with Glenn from Toyota who calls me every once in a while to check and see if the car is still acting up. They claim that because it is hot outside that the car tries to back off drawing from the battery until it cools down. It seems hard to believe that they have a proving ground in Mesa, AZ and they did not discover this during the endurance testing...

If you would, please call Power Toyota at (480) 598-2400 and speak to Lowell in the service department. He currently has 2 vehicles that are exhibiting these symptoms and any additional vehicles/information about this issue is being sent back to Toyota via their rep for research. Hopefully they will find a solution soon. My gas mileage has dropped from 50 mpg to 41 mpg because of this!

 

Snarf44, it really is random. I have had it happen to me on days that it was 105-108 outside and I have had days that it was 115+ and it never happened.

Yes, I lose all power from the electric drive system. It is almost as if the traction battery has one or two bars left (even if it shows more) and the engine revs excessively and you don't go anywhere. It has nearly caused me to have an accident coming home in rush hour traffic on the freeways.

It happened to me today, in fact. If you begin to notice it doing this, briefly turn off the radio and the A/C and you can hear the fan in the battery pack working hard. My guess is that the electric drive system goes into some sort of failsafe mode too soon and causes is to partially shutdown. When my Prius does this, the engine runs constantly at stops and will not go into stealth mode, even if the battery has 5 or more bars on the display. I have also noticed that once the electric drive system comes out of failsafe mode, my gas mileage drops by at least 8-12 mpg. I used to get between 49.5 to 52 MPG until this started. Now I am lucky to get anything over 42 MPG.

If you know of any more people that are experiencing this issue, please have them call and report it. The more people that report it, the sooner we will have a fix available!

 

I did ask the dealer and the Toyota rep if this could be an inverter issue or a battery ECU issue when I first brought the car in and was told that there was no way that anything electrical could be defective without producing the red triangle of death or at least a trouble code. My Prius has not generated any trouble codes or RToD's.

I have checked the vent during one of these episodes and it pulls air nice and strong when it is running on high. A/C is an absolute must in this desert heat, yet the interior (or exterior) heat does not seem to make it any worse or better (i.e it doesn't always do it if it is over a certain temperature).

What's funny is that I don't remember it doing this last year. Hopefully this is not a battery issue since the car is now over a year old...

 

I had experienced similar behavior in my '04. See my thread titled something like "No Help From Battery In Drive". I was getting the red triangle of death and code U011 though but the behavior was just as you say - no accelleration - the ICE just isn't up to the task. My problem was fixed about 1600 miles back by replaing the Battery ECU. I also had no charging of the battery when the problem was occuring.

good luck and keep us posted,
jim

 

I have to agree with Dr. Evan. Considering that this vehicle has one of the most robust self diagnostic systems in any production vehicle, if it isn't generating any codes for you, there is nothing technically wrong with the vehicle. The battery is probably over the acceptable operating temperature and the vehicle will leave the battery alone until it reaches the operating temperature range that is acceptable to the computer. That means reduced performance until the battery compartment temperature is acceptable. No codes means no problems, doesn't mean no performance issues.

I'm inclined to believe that the variability with regard to when the vehicle exhibits a lower power problem won't be directly related to outside temperature. I think factors such as time outside, amount of sun exposure, ambient temperature inside vehicle and any direct sunlight in cargo compartment would effect when this problem shows up.

I'm not so certain this will help, but exchanging vehicle air with outside air while the vehicle is sitting with one of those cheesy solar vehicle ventilators which fits atop the edge of a side window might be helpful.

 

I agree that the temperature of the battery and the battery compartment is the primary cause of the issue. Toyota (Vehicle Technical Services) seems to think that it has to do with the ambient temperature of the air instead. My guess is that the setting for the max ambient battery temperature is set conservative and needs to be adjusted. I know that this would shorten the life of the battery. It is just very strange that the problem is not consistent. I have had the car out in the open sun all day in 115+ degree temperatures with 175 temps in the interior and not have a problem. I have also had the car in a garage all day with ambient temps of 105 and 105 in the car and have the problem show up immediately. My thought is even though the computer does not generate any codes for this does not mean that there is not an issue here.

It seems strange that they have a proving ground in Mesa, AZ and did not run across this during their testing. Toyota Technical Services assured me that very extensive testing was done here in the desert heat to see if the car is capable of withstanding the climate, and it passed with no problems.

 

when you use current from the battery it's a chemical reaction and as such produces heat. By the same token when you charge a battery it produces heat. When you have a 100+pound battery getting hot from the chemical reactions going on and a high ambient temp the internal battery temp sensors read this a a potential problem and tells the computer to limit current input/output. To start it the current draw as far as I can tell from the miniscanner on a 2k3 is about 30 amps and when the car starts just sitting there it charges about 9 amps then you start moving and it draws 27 or so amps, then when you come to a stop at the end of the block your charge about 14 amps and if the ambient is high the battery pack gets over heated in short order. If I ever get to a place where the ambient is really high I'll moniter the internal temps of the cell packs. Sorry here hot is about 82F maybe getting to 88F so it's probably not going to ever happen.

 

One thing you might do if you think that having the car sit in the heat is causing the batter to get too hot is to install a solar fan. I had one of these in a car I owned years ago to keep it from super heating when parked in the sun all day. It was a little fan that straddled the rear window that had a small solar panel that hung outside the window. The panel was only about 1.5" by 12" and had rubber spacers that you could cut to fit any window so you had a good seal. It drew outside air through the car's vents and exhausted it with the little fan in the unit. It helped keep the car from superheating when it was sitting out in the sun all day.

 

One telltale sign the battery is overheated, is that its fan would run doubletime. If the fan isn't running fast, then the battery probably isn't too hot.

 

True, but my thought is maybe the thermal cutoff is set too low. I know that this protects the battery, but maybe more research needs to be done in what the temperature of the battery pack reaches in the summer heat and how changing the setting will affect reliability.