I think my battery was dying out yesterday....

Yes, the internal combustion engine turns on ... even at very low speed or sitting stationary, if the traction pack is low. But if you accidentally (or deliberately) had it in neutral, the ICE will NOT turn back on. That may have been what happened, if the ICE never started. Similarly, if the ICE is running and it's in neutral ... she no charge.

.

 

Stay in D or P and everything will take care of itself.

Tom

 

I'd guess that when you parked it you somehow left it in IG-ON or ACC instead of shutting it completely OFF, and were draining one or the other of the batteries. Always lock the car, and if it is not OFF it will give a long beep.

 

I drive an '08, so I have a vested interest in issues such as this being
resolved satisfactorily. Here's my take...

I think the genesis of this "condition" was solely due to low HV battery
State of Charge, SOC.

At very low speeds, that is very low torque requirements, the HSD
tends to use the HV battery most if not all of the time. If you were
watching the MFD Consumption screen, the one with the fat yellow
bars, everything would look fine; 100 MPGs minute after minute. But if
you where watching or had switched to the Energy Monitor screen, the
one with the colored arrows, you would have seen the SOC slowly
dropping into the two-bar red zone. From time to time the ICE would
come on and charge the HV battery up to three blue bars.

I suspect that you left the highway with three blue bars, a very low
SOC. Driving acros the lawn left you with just enough SOC that three
blue bars just barely showed and the ICE did not come on to recharge
the HV battery.

On the face of it, this would appear to be a 12v battery issue. I cannot
resolve what meaning this has. Sorry.

Flooring the car in Park appears to do nothing to increase SOC. I tried
this just a few minutes ago and the Energy Monitor showed no arrows
pointing towards the HV battery, so I would assume no energy flow.
If anything, just sitting there with the car in Ready results in a continual
slow draw on the HV battery.

(There is a technique called "force charging" where you put the car in
Drive, step firmly on the brake to keep the car stationary, and then
step on the gas. In this case yellow arrows do appear indicating
charge going into the HV battery.)

From my close observations of the energy flows when the car is
operating at speeds under 10 MPH, this is exactly what I'd expect, but
there is a little surprise to consider. The HSD or more properly one of
the computers seems to use 8 MPH as a signal for a control algorithm
shift.

When your foot is off the accelerator, the "go-pedal," above 8 MPH the
default energy flow is blue arrows into the HV battery from regen.
However, with your foot off the go-pedal below 8 MPH, the default
energy flow is yellow arrows out of the HV battery to MG1 through the
Power Split Device and then to the front wheels, moving the car ever
so slowly forward.

So, when poking along in a traffic slow-down at speeds around 5 MPH,
the HSD is drawing on the HV battery even if you're not consciously
pushing on the go-pedal. And you draw on the HV battery each time
you skooch the car forward a little bit to close up.

There are two ways to avoid constant HV energy draw in this
situation:
* push slightly on the go-pedal to get into "no arrows" glide on the
Energy Monitor
* when at a stop, press firmly on the brake pedal to stop the slight
yellow arrows flow.

Lastly, when you are sliding along at less than 10 MPH, always watch
the Energy Monitor so you can see what the state of SOC is and which
way energy is moving into or out of the HV battery.

Hope this helps.

 

Creeping in traffic will discharge the traction battery. At 2 (pink) bars the ICE will cycle on & off. You saw the results on the MFD. Add the load from the AC & everything happens faster & the situation lasts longer. There is a noticeable reduction in available power at 2 bars but will not last long. You didn't see any green cars because the brakes didn't generate any electricity. At 5mph all braking is mechanical. I can't help with your window "problem". Was the car turned off?

 

Keep in mind that running the HV battery down to purple bar will have no affect on the 12V system. There is still plenty of power for the 12V system, which is driven by an inverter from the HV battery. If your 12V system voltage is low it can only be from one of the following:

1) Not in Ready mode, so the ICE cannot recharge the HV battery, leaving no power for the 12V system.

2) Failed inverter so that the 12V system does not recharge.

3) Shorted 12V battery dragging down the 12V bus.

Number 2 & 3 are pretty unusual.

Tom

 

Comments by others have highlighted the fact that my earlier
comment about the window issues being related to the 12v battery is
misleading. When the car is in the Ready condition the 12v system --
which includes the window motors -- is kept at 13.6-.8v by the HV
battery through the DC-DC converter [name?]. So even if the SOC
shows red bars, the 12v system has plenty of power. I still can't make
head nor tail of what the window issue means.

Now this is a whole different kettle of fish! When running on HV
battery power alone, you see 100 MPG not 5.

It took me two days to puzzle through what I know to put together my
earlier post. I'm gonna have to think on this for a bit. In the
meantime, with luck the folks with a really good understanding of how
the HSD operates at low speeds may come up and post.

I'll leave you with this. The graph of theoretical maximum MPG tops
out at ~100 MPG at 21 MPH. As you go faster, it gradually decreases
to ~60MPGs at 60 MPH. When you go slower than 20 MPH, the graph
dives very steeply to 0 MPG at 0 MPH. So it would not surprise me
that you were saw 5 MPGs at 5 MPH when the Internal Combustion
Engine, ICE was running.

 

by chance can I get a "prius for dummies"?

Every time I think I have it figured out, I get thrown a curve ball.