Does regenerative braking trip the brake lights?

Yup, and just to be clear, several owners -HAVE- exited their car from the passenger side, due to close parking in underground lots etc. Some have even damaged/destroyed the 12V battery doing it.
One owners son drove him/her to a store and waited in the car, listening to the stereo, until shopping was done. The 12V battery was fully depleted (which makes me think it was a her as most men can't shop that long ). They thought it was the stereo, but the lights didn't go out, and they draw a lot more than the stereo (unless, of course, you happen to have a boom box car).

 

Hello Tom:

As far as I can see you are correct: to get the windows down or up, you need to cycle from "accessory" to "on"; then to "off", and then back to "accessory", to get back to only playing the radio.

It's just that "accessory" on the Prius may do less than current "regular" autos, such as not be able to put the windows up or down. The other big difference is that there is no "rotary key switch" on the Prius, so instead of switching from "on" back to "accessory, you have to first cycle through "off". That sort of bothers me also. Buy I've gotten used to it.

As far as why the battery goes down more quickly (and I assume that you are referring to the SOC meter for the traction battery): my observation is that most everything is energized in "on" mode that would be energized in "Ready" mode, except that the ICE cannot run. Maybe someone here knows better and can enlighten us on this.

Anyway, in "on" mode, I assume that there are other system functionalities that are drawing electrical power (such as the cabin fan, traction battery fan, etc), which eventually comes from the traction battery. Included in this would be the 12v battery, which gets is power from the traction battery (I think).

Best wishes,

 

The various Prius power states that you can enter are similar to the power states that you can select with a normal automobile that has a key ignition. With a normal vehicle, you can select accessory position to listen to the radio or ignition on (where the engine has not started and where electrical drain is quite high).

Here is a list of the four Prius power states:

IG-OFF: all systems turned off
ACC-ON (first push of POWER button w/o depressing brake pedal): MFD is on, you can turn on the stereo system, no dashboard lights are on. 12V battery drain is relatively minimal here.
IG-ON (two pushes of POWER button w/o depressing brake pedal): Most dashboard warning lights are on, you can raise and lower windows. As you discovered, do not leave the car in this state for any significant period of time as 12V battery drain is quite severe. This is because the powertrain electrical systems are consuming power but since the vehicle is not READY, the 12V battery is not being charged.
READY (depress POWER button while brake pedal is depressed): The car can be driven.

There's nothing wrong with the procedure that you indicated for lowering the windows.

 

By now I think you've received all of the info you need, though I don't know that anyone has answered this question within your post. The real issue addressed in the series of posts above is that you can drain the 12V battery, pretty easily in fact, by leaving the lights on. The headlights, in particular, draw a significant amount of juice from the little 12V battery in our cars. If you leave the headlights on, they will be turned off automatically after you exit the car -- but you have to open the driver's side door to make this happen.

So, if you sit listening to the radio for 20 or 30 minutes while in the On position, and the 12V battery is in good shape, you should have no problem. If the headlights also are on this entire time, you'll be placing a heavy drain on that 12V battery. If you draw it down far enough, you'll damage the battery. Eventually, you would get to the point where the car will not start. Worse, of course, is if you walk away from the car, leaving the headlights on. It will do more than kill the 12V battery!

 

+1 on what Patrick said -- he's Da' Man on technical stuff like this :cheer2:

I'll add this for the sake of completeness, or overkill

In the following, the voltages come from my ScanGauge, which will
read voltage even in IGN-OFF. :rockon:
IGN-OFF: On a strong 12v battery, readings in the mid-high 12's are to
be expected.
ACC-ON: readings in the low-mid 12's.
IGN-ON: again, readings in the low-mid 12's, but relatively quickly
dropping into the high 11's. Note: this means that 12v battery is not
being sustained/refilled by the HV battery, same as in IGN-OFF and
ACC-ON.
READY: readings in the high 13s-low 14s are typical as the HV battery
is keeping the 12v battery topped off. Note: Only in this state will the
HV battery, the green/blue/purple bars on the batery mimmic,
decrease over time, and the 12 v battery stays topped off. The good
news is that should the HV battery go "into the red," actually purple,
the ICE will start-up and typically run until the first blue bar is
showing.

Again the readings come from my ScanGauge. Here is another
excellent reason to get one. You can listen to the radio in ACC-ON with
the least 12v battery drain, yet monitor the status of the battery and
at some preselected voltage, for me 11.5v, put the car in READY to
top off the 12v battery from the HV battery.

If this keeps you from running the 12v battery down to the dangerous
level of 10.5v even once, you may have saved the cost of a premature
12v battery replacement... which costs about as much as the SG, with
which you also get the on-going benefits of higher FE, and error code
reading and resets.

You can get your ScanGauge at the PriusChat Store.