Intermittent Battery Function - huh?

[leafcutter]

2007 Prius, 16k miles.

Has always run perfectly well, no problems. I am currently in the middle of a long trip (2500 round trip) and was wondering how it would perform in wide open spaces.

Yesterday, the battery started fritzing. As far as I can tell, it RANDOMLY will stop taking a charge while driving. The Battery Bars slowly fade down to a single purple or none at all, and the mileage drops to 20-25 mph on the flats as the engine desperately tries to charge it up. Even going down long steep mountains, mpg gets up to about 40 only while coasting, and the battery will not charge more than 2 purples, despite all its trying.

Then, after 20 or 100 minutes, BAM, the battery charges up, the mileage goes up and all is well for another 20-100 mins, then it starts again.

I find no relation to AC use, screen touch, radio or nav use, switching to D or B or N, use of the plug in phone charger, etc etc etc. No change in driving habits, terrain, temperature, moisture, etc. No change in car load. The local 'regular' gas is 85 instead of 87, but I cant imagine that has anything to do with it.

Anyone have this happen before or know what to do other than hope the dealer will know how to fix it? Seems to me like theres a loose circuit or wire somewhere.

[efusco]

I don't like the sound of that. could be wrong, but I've heard similar descriptions for the few prior battery failures reported in the past and it definately should never drop into the pink/purple range during flat cruising.

Get it checked ASAP before you have an all out failure.

[Patrick Wong]

Since you did not report seeing any warning lights on or MFD icons appear, it might be hard for the dealer to do much at this time. However I agree that your symptoms sound like early warning of a pending traction battery failure.

[efusco]

Originally Posted by Patrick Wong

Since you did not report seeing any warning lights on or MFD icons appear, it might be hard for the dealer to do much at this time. However I agree that your symptoms sound like early warning of a pending traction battery failure.

While there may be a diagnostic fee, shouldn't they be able to physically test the battery even w/o warning lights?

[Patrick Wong]

Originally Posted by efusco

While there may be a diagnostic fee, shouldn't they be able to physically test the battery even w/o warning lights?

Yes, I suppose the tech could obtain a readout of the voltages produced by each of the 14 module pairs.

[leafcutter]

Update.
The dealer found nothing wrong, with the battery working fine and the digital log reporting no events.
The car has never had the problem again.
Reading the manual the other day I was reminded about the air-intake grate responsible to help keep cooling air flowing to the battery..... right next to the right rear seat.....
We had blankets and pillows stacked in the back with carseat and kid paraphenalia in that location when the problem happened. It was the only time we have loaded up the backseat, and the only time the battery fritzed and kept conking out.
So, looks I blocked the vent. Live and learn.
I'd have wished that the dealer/mechanic might have thought of it, but these cars are new I suppose and there's a learning curve here.

Thanks for your comments.

[qbee42]

That makes sense. A hot battery.

Tom

[Shawn Clark]

I have to give some credit to my salesman, he was very specific in warning about this sort of thing happening if we obstructed the vent. (He also said it might stink while the battery was hot.)

Why doesn't Toyota have a battery temp. indication or idiot light for very high/very low temp? I would like to have the battery temp right there next to the bar graph on the display.

[V8Cobrakid]

I've been doing long open road trips for the last two weeks. I've noticed that i lose all battery help. I kept the vent open at all times with A/C on at all times.

I've done this in the past with + results.. same routes...

i empied out my car and my friends are realizing that the rear metal under the seat is almost hot enough to burn... i have yet to feel it. we load up the car tomorrow so we may continue home.

I couldn't stop thinking about getting a scanguage...