Random Beeping = Dead Battery...

Use the diagnostic mode on the MFD to check the 12v battery voltage. My 1st battery lasted 3 & a fraction years so yoiu are due. Since you already had to jump the car I'd expect to see low voltage readings. If the car won't start, keep trying. It may boot up on the 3rd try.

 

Uhh, what low-battery warning light?

The easy no-tools battery test procedure is found here:
http://priuschat.com/forums/newbie-forum/73400-weird-stuff-happening-mpgs-dropping-test-battery.html

 

Sorry, I wrote carelessly. Lots of people have had dead or dying 12V batteries with no warning from that light. It is easily possible that yours is dying also. The beep could very well be a symptom; any number of odd things can happen when the battery gets low, depending on which computer starts to suffer first.

 

I have experienced this same problem at least 3 or 4 times. The first couple of times I didn't know why I had a dead battery. The next 2 times, I had taken note of the random/unexplained beeping before locking the car for the night. (Beeping goes away after the car is locked but the battery is dead in the morning.) I could not find anything about this in the manual of course. A few times since, when I noticed the beeping I powered the car on and off and attempted to shut it down again. It seems to need the car to be powered on to the "Ready" state before shutting back down, though I had to try it a couple of times this evening before the beeping went away. It also might have helped to put it in gear, move a bit, and then put it back into park and shut down (or maybe it just needs to be on for a few seconds???) I find this anomalous behavior rather disturbing. I plan to call Toyota and see if I can get any information out of them. Maybe they have a software patch for this bug.

 

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Dealer just diagnosed my car with a dead 12V battery. Symptoms: right after getting gas, the red brake light came on with associated buzzer, as did the check engine light, triangle with exclamation pont, ABS and VSC warning lights. Tried to shut off and turn car back on but wouldn't for about 15 minutes, then started. Lasted another 4-5 miles, happened again but car just shut down. 15 minutes later started and again it occurred about 10 miles later. Got it to Toyota and they diagnosed it as a dead 12V battery and replaced it. Ran fine for a day and it they occurred again (in my driveway luckily) and found the battery was once again dead! They have had it two days without any diagnosis....any thoughts appreciated. Ready to sell and look for an Altima or Insight....I drive 100 miles a day and need a reliable car! Besides my headlights turn off every 5 minutes and if I miss one, the other goes and it is then very dark...different annoying problem I have lived with for two years. Thank you to anyone with thoughts on this battery issue! I've given up on the lights.

 

My guess is that the DC/DC converter within the inverter is working intermittently. That would cause the 12V bus voltage to sag, causing the various warning lights to appear as you described. This would also explain why the replacement 12V battery failed. The inverter is covered by the 8 year/100K mile hybrid system warranty.

Regarding the headlights, I assume you have HID. I suggest that you take a photo that shows one headlight lit while the other is out, and ask your dealer to take care of that problem as well so that you don't have to live with a safety issue. Good luck.

 

Another possibility: if 3rd party or aftermarket electronics are present, they could fail and drain the battery without setting any error codes.

 

CJarvis-

It's been a while since you posted anything- I hope your e-mail is still current. My 2007 prius just started to have the exact same issue you are describing in your posts. The dealer also just replaced the battery - and as you said, it just died in my garage.......killin me!

What did they tell you in the end? I can hardly afford to drop it with them for 3 days of testing so any help would be great! Thanks!

 

I know it may not be the case, but make sure you actually put the car in PARK before you turn it off. Leaving it in either ACC or IG-ON can cause the beeping and also will run down the 12-volt battery. Running the battery down several times will cause it permanent damage.