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Dead Battery - Page 5

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Posted by Pete Granzeau on February 29, 2008, 7:31 pm

As I understand it, the two 12V power outlets are turned off when the
Prius is shut down, so they can't be used to provide power to turn the
beast back on.  You are back to a battery jump, I fear.

The comment by "Mr. G" is incomplete.  The 12V battery continues power
to the SmartKey sensor system and the remote access system when SmartKey
is not installed.  There are several sensors, I believe, and they are
enough drain on the 12V battery to make the car go dead after a couple
of weeks of being unused.  Other things in the car still have power,
such as parking and brake lights, internal lighting, and even (I would
bet) the clock in the radio, and if enough of those things were left on,
there might be an even greater drain on the obviously inadequate 12V

Posted by Mr. G on February 29, 2008, 9:27 pm
(pgranzeau@cox.net) says...

Yes, thanks for catching my mistake.  I was thinking along the lines of
accessories, etc.  But the 12V must also power all the various
electronics that are always 'on', if even in a sleep mode.  I have no
idea what the SKS draws, but it's probably one of the more significant
drains on the system.

There is not only the drain from those things that any car would have,
but other items unique to the Prius, such as the coolant pump (though
that's a one-time thing when you shut down).  If I go into my garage
when my Prius is just sitting, it's not unusual to hear it make various
whirring and clicking sounds.  One of these I understand to be the brake
actuator, which usually can be caused to kick in if you step on the
brake pedal with the car off.  The manual mentions a pump in the back
that checks for leakage from the batteries.  And there are any number of
other various noises which I'm at a loss to explain.

So yes, that tiny 12V battery has a lot to do while the car sits idle.

Posted by Elmo P. Shagnasty on March 1, 2008, 12:54 am
 In article

It would, IF the dashboard power outlet were live.

It's not live until the system is in Ready--and that requires the 12v

Posted by richard schumacher on March 1, 2008, 5:04 pm

It is simple to modify one of the two outlets so that it is always live
and therefore can be used for a jump.  Of course then it is also always
available to drain the battery through an attached accessory.

Posted by Marilyn & Bob on February 28, 2008, 3:17 pm

Once the car is in Ready mode, the 12V battery powers nothing.  All the
electric power comes from the traction battery and the motor/generator.  So
using your wipers, electric defroster, lights and heater motor while driving
will have no impact on your 12V.

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