Prius turn on and off repeatedly!!!

[JSH]

I just had something really weird happen to me today. I went out to roll up the windows and move my Prius. Everything was fine at first. I pushed power and rolled up the windows. I then hit power again and turned the car off. Everything was normal.

However I decided to move the car about 15 seconds later and the car wouldn't power up. The MFD just started rapidly blinking the start-up screen and all the warning lights came on. I tried to turn the car off but pushing the button didn't do anything. I then inserted the key fob and the car powered down when I hit the power button. (The car flashed the start-up screen for ~ 30 seconds)

I then attempted to start the car again and again it wouldn't start and went into a continuous loop of powering on then off. This time it was a longer cycle of about 3-5 seconds and the A/C powered up in the cycle. I again tried to turn the car off but pushing the button had no effect. I tried to remove the fob but it wouldn't come out until I turn off SKS by pushing the button on the lower dash. Then the car powered down.

I attempted to start the car a third time and it powered up like normal. I drove around the block and parked it with no problems.

Any idea what would case the car to go into a continuous loop of powering on and off? (No, I didn't push the power button multiple times)

[qbee42]

Low 12V battery is my first guess, or a bad connection to the battery or ground.

Tom

[richard schumacher]

Most likely, if that is the original 12V battery. Measure the voltage at the jump point under the hood with the car OFF, or use the selftest procedure:
Checking 12v Battery Health - Hybrid Car Forums

[Flying White Dutchman]

copu past from that link above

--------

Checking 12v Battery Health
You can easily check out your battery status/charging system using the MFD in maintenance mode. No tools required.
Get your Prius into "Accessory Mode" - Press the power button without touching the brake pedal.
Put the MFD into "Maintenance Mode" - Press and hold the "Info" button on the MFD while turning the headlights on and off 4 times.
Press the "Menu" field on the screen.
Press the "Display Check" field.
Press the "Signal Check" field.
The 12v battery voltage will be one of the items listed, it should be above 12 volts. If it is lower, either the battery needs replacement or the charging system is not functioning correctly - see step 7.
Put a small load on the battery by pressing the power button again without touching the brake pedal. The voltage should stay above 12v. If it drops significantly, you need a new battery.
Now get your Prius into "Ready Mode" - step on the brake and press the power button. The battery voltage should immediately rise to 13.8 volts (Your Prius uses constant voltage charging). If it is lower, the battery will never charge; if it is much above 14 volts, your 12v battery will get cooked.
Shutting the car down will reset the system back to normal operation.
If you need to get a new 12v battery, you can opt for a dealer replacement or get a better battery at a lower price at: 12 Volt (12v) Toyota Prius Auxilary Battery for 2004, 2005, 2006, 2007, 2008 and 2009 with installation kit and free shipping
and install it yourself.

JeffD

[JSH]

Originally Posted by Flying White Dutchman

If you need to get a new 12v battery, you can opt for a dealer replacement or get a better battery at a lower price at: 12 Volt (12v) Toyota Prius Auxilary Battery for 2004, 2005, 2006, 2007, 2008 and 2009 with installation kit and free shipping
and install it yourself.

Thanks for the testing procedure, I'll check battery voltage tonight. The car did start up like normal this morning when my wife went to work.


Some questions on battery replacements:
How much is a stock Toyota battery? $168 for the optima kit (now reduced to $138) is about twice what I expect to pay for a battery.

I also see that Auto Zone stocks the following battery for the Prius:
Duralast 51R-DLG
27.7 lb
500 Cold Cranking Amps
650 Cranking Amps
8 year warranty with free replacement for the first 3 years
$89.99

That seems to be a more reasonable price for a battery.

[jayman]

If that Autozone battery is the correct sealed battery with proper sized posts, and provision for the external vent tube, go for it.

I'd ask to see it first

[2009Prius]

Originally Posted by JSH

...

I also see that Auto Zone stocks the following battery for the Prius:
Duralast 51R-DLG
27.7 lb
500 Cold Cranking Amps
650 Cranking Amps
8 year warranty with free replacement for the first 3 years
$89.99

That seems to be a more reasonable price for a battery.

Yes this seems a much better deal if the battery does fit. Please let us know how it works out for you. Thanks and good luck!

[JSH]

Originally Posted by jayman

If that Autozone battery is the correct sealed battery with proper sized posts, and provision for the external vent tube, go for it.

I'd ask to see it first

I'll do that. The description says that it vents to the outside.

[Bear68]

Bear in mind the factory original 12VDC battery is rated at about 325 CCA and I don't believe it will weigh in at anything near 27 lbs! I would believe 12-13 lbs at the max. I routinely lift them in and out one handed......

[JSH]

According the the diagnostic test the battery is dead. When I first went into the diagnostic screen the voltage was 11.5. This dropped to 10V when I hit power then up to 14.2V when I hit power again. So it seems the battery is dead and the car is cooking the battery trying to charge it.

I'll explore my options a bit more next week. Right now I'm getting ready for a 5 day motorcycle trip. I'm just happy to know that nothing is wrong with the car.