Dramatic Loss of Power/Performance in My Prius

[jw_teacher]

This all of a sudden happened yesterday afternoon when I drove home from work...

Everytime I touched the gas, the car would stall for a good second or two then weakly start accelerating. There was nothing wrong with the battery charge as it was only one or two bars under full. I did not have the air conditioning on (to save gas) and had the windows partially open. However, in the back seat the exhaust vents for the battery were very loud, louder than I've ever heard them before.

It was like that again this morning and afternoon. My Prius is not performing the same on the road. Granted, I live in the midwest and it is over 100 degrees here. But I don't think that could be the reason for the loss of power. Any suggestions what could be wrong?!?

[San_Carlos_Jeff]

<div class='quotetop'>QUOTE(jw_teacher @ Aug 1 2006, 04:12 PM) [snapback]295878[/snapback]</div>

This all of a sudden happened yesterday afternoon when I drove home from work...

Everytime I touched the gas, the car would stall for a good second or two then weakly start accelerating. There is nothing wrong with the battery charge as it is only one or two bars under full. I did not have the air conditioning on (to save gas) and had the windows partially open. However, in the back seat the exhaust vents for the battery were very loud, louder than I've ever heard them before.

It was like that again this morning and afternoon. My Prius is not performing the same on the road. Granted, I live in the midwest and it is over 100 degrees here. But I don't think that could be the reason for the loss of power. Any suggestions what could be wrong?!? [/b]

Sorry, no suggestions, but you should be concerned. I've driven in well over 100 degree temp and the power feels like it always does. I'd take it in as soon as you can.

[efusco]

If the battery is overheated (car sitting in the sun for an extended period of time or recent heavy use (ie. charging/discharging)) it certainly could result in decrease performance. Based upon the fact that you could hear the fan running hard to cool it that would be my main suspicion.

How did it run after sitting all night in cooler temps? If performance was still off first thing in the morning I'd be concerned. If it's only after sitting in the sun for a long time and it's just a mild/moderate decrease that could be explained by decreased battery performance I wouldn't worry.

Not being there it's darn hard to know exactly what you're describing, but if it's bad morning and evening when you know the battery should be cool definately have it checked.

If you don't have a CEL and it's otherwise doing OK when cool then you can wait and watch.

[eagle33199]

the temperature in the battery compartment does determine the amount of power that can be extracted from the battery... as it gets hotter, the battery becomes less efficient. It's possible that, sitting in the sun, the car got extremely hot, including the battery compartment, and needed to cool down before it could provide max power (thus the fans straining). having the windows open instead of using AC could have delayed battery cooling, as the air temperature in the cabin wasn't cooling quickly. I'd recomend trying a comparison in similar situations of running the AC for a few minutes first to help rapidly cool the cabin temperature and see if the problem goes away. if it still has a problem with a relatively cool cabin, then i'd definately be worried and take it to the dealer.

You could also always get a can-view to see exactly whats going on with the batteries and the power and such.

Darn EFusco, you beat me to it! posted almost simultaneously!

[john1701a]

<div class='quotetop'>QUOTE(San_Carlos_Jeff @ Aug 1 2006, 04:14 PM) [snapback]295882[/snapback]</div>

I've driven in well over 100 degree temp and the power feels like it always does. I'd take it in as soon as you can.
[/b]

I wouldn't. That's sounds exactly like my 102 F degree experience. The system simply went into battery-pack protective mode. The heat most definitely was to blame. All was fine after that single incident.

[jbarnhart]

From the description, it almost sounds like the "traction control" is kicking in. Is there any indication on the dash? Maybe there's a bad sensor or something.

[jw_teacher]

Yes, in all cases my car was sitting out in the sun. I left 10 o'clock this morning and it was well above 90 degrees. It was over 100 degrees both afternoons. I never tried the car at night.

I guess I have to be more careful to keep the battery cool prior to using it.

<div class='quotetop'>QUOTE(efusco @ Aug 1 2006, 04:19 PM) [snapback]295886[/snapback]</div>

If the battery is overheated (car sitting in the sun for an extended period of time or recent heavy use (ie. charging/discharging)) it certainly could result in decrease performance. Based upon the fact that you could hear the fan running hard to cool it that would be my main suspicion.

How did it run after sitting all night in cooler temps? If performance was still off first thing in the morning I'd be concerned. If it's only after sitting in the sun for a long time and it's just a mild/moderate decrease that could be explained by decreased battery performance I wouldn't worry.

Not being there it's darn hard to know exactly what you're describing, but if it's bad morning and evening when you know the battery should be cool definately have it checked.

If you don't have a CEL and it's otherwise doing OK when cool then you can wait and watch.
[/b]

I will make sure to run the A/C from now on as long as it is this hot. I had no idea the battery couldn't sustain 100 plus degrees weather.

<div class='quotetop'>QUOTE(eagle33199 @ Aug 1 2006, 04:21 PM) [snapback]295889[/snapback]</div>

the temperature in the battery compartment does determine the amount of power that can be extracted from the battery... as it gets hotter, the battery becomes less efficient. It's possible that, sitting in the sun, the car got extremely hot, including the battery compartment, and needed to cool down before it could provide max power (thus the fans straining). having the windows open instead of using AC could have delayed battery cooling, as the air temperature in the cabin wasn't cooling quickly. I'd recomend trying a comparison in similar situations of running the AC for a few minutes first to help rapidly cool the cabin temperature and see if the problem goes away. if it still has a problem with a relatively cool cabin, then i'd definately be worried and take it to the dealer.

You could also always get a can-view to see exactly whats going on with the batteries and the power and such.

Darn EFusco, you beat me to it! posted almost simultaneously!
[/b]

Thank you. Now I know it is a common occurance under this scenario and not a problem with the car itself.

Thank you everyone who replied.

<div class='quotetop'>QUOTE(john1701a @ Aug 1 2006, 04:24 PM) [snapback]295891[/snapback]</div>

I wouldn't. That's sounds exactly like my 102 F degree experience. The system simply went into battery-pack protective mode. The heat most definitely was to blame. All was fine after that single incident.
[/b]

[richard schumacher]

I will make sure to run the A/C from now on as long as it is this hot. I had no idea the battery couldn't sustain 100 plus degrees weather.
[/b]

This is why the battery vent is inside the cabin. The battery needs about the same temperature range that people find comfortable. I don't think that the owner's manual makes any mention of this, which is unfortunate. Imagine how many owners might be seasonally sweating and freezing under the mistaken impression that they are helping their fuel economy.

[naterprius]

I can reproduce this condition.

A. Drive car to work, park in sun.
B. Go out for late lunch, about 1.5 miles away, around 2:30 pm.
C. Park car in sun again.
D. Leave for home a little early (say 5:00 pm).
E. Car will run in sluggish mode with only one bar on the battery. Vent fan is on in the backseat on high, you can't miss the sound.


The key here is the late afternoon hot soak. The batteries are very hot from my lunch jaunt and had no opportunity to cool since the ambient air in the car is up over 120.

Going to lunch earlier helps, so does parking in the shade. (I already have tinted glass and a sunshade)!

You may also be able to prevent this by letting the vehicle run for a few minutes before driving off. (I know, crazy, huh?).

Nate

[RichBoy]

did you leave the parking brake engaged ? if not, the take it to your Authorized Toyota Dealer ASAP