Dead 12V Battery Or Something Else

You need to either charge or replace the 12V battery. It doesn't seem reasonable to expect the dealer (at no charge) to fix the problem since driver error caused the problem...

 

+1

It is probable that those three hours was the straw that broke the
camel's back. To begin with, the typical service life of the 12V battery
is ~4 years, shorter if it was ever jump-started.
So replacement is in order.

The battery is much smaller than most folks expet as it doesn't need to
crank the engine on start-up.(It is under the hatch-area floor. It just
needs to boot the various CPUs -- maybe 14 of them. With low power
the CPUs apparently send bogus data and the system goes bonkers.

It seems that when it came to the 12V battery some engineer on the
Toyota staff was strongly influenced by Lucas...
"The Prince of Darkness."

The 12V battery is not covered by any OEM warranty. If you're real
nice, or there is something in your purchase contract, it is remotely
possible that your dealer may replace it gratis.

Good luck.

 

It depends on what lights you're talking about.

Anyway the Prius only has a small 12V battery because it doesn't need to crank the engine. So yeah you do have to be kinda careful wit it.

• Tip. If you've left lights or something on and run the battery down and it's still got some power but not enough to start. The best thing to do is to turn off power to everything that you can, then just leave it sit for 30min to an hour. Sometimes the battery will regain a little bit of *charge after sitting for a while and it might be just enough to get it to ready (at which point the inverter will start charging the 12v battery from the power in traction battery and you should be able to drive it to charge some more).

* technically it's just the charge that it already had redistributing within the electrolyte.

 

side note/ went to the dealer for an oil change and they checked the back battery as I watched. Since I wasn't allowed in the shop, are there caps to check fluid levels or did they just check the general appearance?

 

In my US 2009 Prius, if you leave the headlights on, they turn off automatically once the car is off and you open the driver's door. (In the 2010, there is a dealer selectable delay: 0, 30, or 60 seconds, and either front door works)

My advice is to NEVER run electrical accessories in a Prius when the car is not READY.

 

Glad to see you got it going ajayre.

Another difference about the prius is that it doesn't have an alternator (not in the traditional sense) so the 12V battery is charged via an inverter from high voltage system when you're driving. BUT it's a relatively slow process. So be careful as the battery may not be fully charged now until you've done quite a few hours of driving.

Hopefully your battery will be fine once you have driven a bit, but be aware that lead acid batteries are sometimes permanently weakened after being run flat, so be careful with it and keep an eye on it for a little while.

There is a really neat little trick with this model Prius, and that's that you can get into some "secret" menus on the multifunction display (MFD) where you can get a read out of the 12V battery voltage. So after the battery is recharged you may like to follow the procedure outlined in the following post to test your voltage.

See: http://priuschat.com/forums/gen-ii-...conditioning-12v-aux-battery.html#post1188923



...............

 

It's a maintenance free battery so my guess is that they would just have visually inspected the terminals for corrosion and possibly also checked the voltage level (with a digital voltmeter for example).

 

Good. I hope that you either allowed the Prius to remain READY for a continuous 8 hour period; or else hooked up the 12V battery to a battery charger for an overnight charge.

Some owners think that running the Prius for 20 minutes will recharge the 12V battery. Then the next day, they are surprised when the car refuses to start.

 

Also learn to use the procedure on post #9, then you will always know the condition of the 12V.