battery ran down

Look in the door jamb, for the label with the manufacture date. If it's well back before your purchase date, say 6 months or more, it stands to reason you bought a car with a compromised 12 volt battery.

We bought in Nov, 2010, the car's manufacture date was Aug, 2009. When we arrived for a test drive they had the car running. For some strange reason...

Fortunately, after the test drive and the car being shut down, the need arose to start it up again, maybe to check the odometer. It was dead, they had to jump it (again ). We made one of the conditions of sale a new battery.

Your case unfortunately is more iffy. Frustrating: maybe you have to go for test drives armed with a multi-meter?

 

There is actually a motor on the transaxle that turns on and "locks" the transaxle, when the car is put into PARK.

When starting, extra power from the battery is needed, when the car has been placed in PARK to turn the motor in reverse to release the parking lock, which is a mechanical "parking pawl" on a transmission with a mechanical shifter.

Apparently stepping on the brake or placing the car in PARK before turning the car to the OFF position with the START-STOP requires more power than just pushing the button to turn off and start the car from the standard rest position. In that case the ICE and motors having no power keeps the car from moving.

 

I tend to stop the car with the brake before turning it off to avoid damage in setting the parking pawl.

What happens if the start-stop button is pushed with the car on the roll? I ask because I know someone who will do that...

 

it works up to a few mph, so is not advisable.

 

There is NO "parking pawl." There is a motor that is actuated with the PARK switch to lock the transaxle.

Basically, the motor will engage, if the brake is held down when the "OFF" button is pressed.

Taking the foot off of the brake before pushing the "OFF" button means that the motor does NOT engage.

Since the transaxle does not have a fluid coupling, the stopped ice and electric motors are all that's needed to hold the car from moving, without the PARK motor being actuated.

That means the PARK motor does NOT need power when the car is turned "ON" to retract.

 

I seldom use the PARK mode. I can't verify it, but the PARK motor likely has sensors that do NOT actuate the motor unless the car is NOT moving.

Basically, if you have the foot off of the brake when you push the "STOP" button, the car shifts to the "B" or motor braking mode, while NOT actuating the PARK motor.

If you have you foot on the brake when you push the "OFF" button, that motor noise is the PARK motor winding in.

 

OK, so, What happens if the start-stop button is pushed with the car on the roll? I ask because I know someone who will do that..

 

Meaning do not press start-stop button with the car on the roll?

 

Nothing should happen unless you hold it for a few seconds. That's the emergency shutoff procedure in case you have a runaway.

 

i was talking about the park button, not the power button. mike has thrown the proverbial wrench in the works with his info on power button with foot on the brake vs off the brake. i have not read that, and don't know where it comes from.

 

Going into PARK means that the park motor is actuated to wind the "parking pawl" equivalent down to lock the transaxle.

That's the noise that you hear after you cut off the car with the stop button with you foot on it.

The parking motor does not activate with the car moving. That's why, if your foot is off the brake, as the dealer stated, the car just stops, like as if you held the button down for three seconds.

When you start the car with the button, the car goes into the ON mode. The ICE will come on or at least the traction motors to top off the 12 volt. Then, when you shift into Drive or Reverse, the action retracts the park motor before it goes into gear.

The little extra power that you save in the 12 volt in shutdown by not activating the park motor can mean the difference of starting or not starting if th car is left idle for a period.

 

If the 12v batt is that weak, its going to fail anyway. You can make the same argument about rolling up the window after shutting the car off. Bottom line is that there's a 50/50 change of being able to start it again.

 

Not if you don't lock the car. Not if you do lock it using one of the rocker switches on the front armrests, and not if you do lock it using the interior mechanical lock controls. You have to try to use the remote (including in SKS mode) to be warned of a door not fully latched.

 

This didn't sound correct, but I had to test it before commenting.

Based on my tests, I must disagree. By shutting down with my foot off the service brake, both in Neutral (and car starting to roll backwards on slightly sloped garage floor), and in Drive (and car starting to creep forward), my transaxle does lock. Park pawl, or motor-driven transaxle lock, I'm not going to quibble about the name, but it clearly mechanically locks. If I then rock the car forward and back, it travels the same several inches as when shut down correctly from Park gear (but without the parking brake engaged).

That would be the same as N-ICE-off gliding, with MG1 and MG2 freewheeling. Far from holding the car from moving, this is a very efficient coasting mode.

The energy of this should be much less than the energy burned by the headlights in the 30 seconds they stay on before turning off in the factory default 30-second auto-off mode.

 

there has to be a detail of the operation somewhere.

 

http://www.evsafetytraining.org/~/media/Electric%20Vehicle/Files/PDFs/Toyota/25%20%20Toyota%20Prius%20HEV%20ERG%203rd%20Gen.pdf
Page 10

 

very nice, thank you!

"when the vehicle is stopped, regardless of shift selector position, the electro-mechanical parking pawl is engaged to lock the transaxle into park by either depressing the P switch or pushing the power button to shut off the vehicle."

"being electronic, the gear shift selector and the park systems depend on the low voltage 12 volt auxiliary battery for power. if the 12 volt auxiliary battery is discharged or disconnected, the vehicle cannot be started and cannot be shifted out of park."