stereo and battery discharge while parked

The battery meter you see is the hybrid battery. It is not used to start the engine. The 12v battery in the back is. Next time you want to idle and listen to music, just leave the entire car on with the "Ready" light lit up. that way when the battery gets low, the engine will run for a little to recharge, and shut back off.

 

There is an interplay of both the 12V and HV batteries when starting.

The following is how the Gen II works, and I believe it is applicable
to the Gen III as well.

The 12V battery is used first. It boots up the various computers and
ECUs and the HSD does a quick check on system components. If all is
well the HV battery is brought on line. Power from the HV battery is
then used to spin Motor-Generator1, MG1, which acts like a starter
motor and spins up the ICE.

If you are in Park and in Ready, you can listen to music and enjoy the
A/C indefinitely. Yes, the HV battery will slowly discharge. But when it
gets to two bars the ICE will come on and recharge it up to say, four
bars, then shut down. How often this happens is a function of how hard
the A/C runs to maintain the set temperature and whatever 12V
accessories you're also using. (See below.) The A/C runs directly off
the HV battery.

Standing alone, the primary use for the 12V battery is the initial boot-
up when starting.

However, when the car is in Park and Ready, all the various
lights, stereo, windows, GPS, CPUs and ECUs, etc, run on power from
the 12V battery. But the 12V battery is quite small. It is kept charged
by a DC-to-DC converter with power from the HV battery when the car
is in Ready. In the ON and ACC modes the poor little thing stands alone
and can be relatively quickly discharged past the point when it can
power the CPU boot-up on starting. This occurs at ~10.5V.

Hope this helps.

 

So, lets see if I've got this straight. If you at, lets say a "drive-in movie" and on non-hybrid cars you would just turn the key to ACC to power up the radio (to give you sound) so you could sit for a few hours and enjoy the movie. This is never a problem, after several hours the car always starts fine.
However, with a hybrid, this would drain your battery to the point where the car wouldn't start? (if you listened to the movie on the radio in ACC mode, obviously you would not have the car running for the entire movie). Is that what I'm hearing?

 

All accessories and computers run off the low-voltage 12V system. The only exception is the air conditioning compressor, which runs off high-voltage.

If the car is READY, the 12V system is powered through the DC/DC converter which reduces the high-voltage from the traction battery to ~13-14V (it needs to be higher to actually charge the '12V' battery).

The traction battery is normally charging whenever the engine is running.

If the car is in any position other than N, it can start the engine to recharge the traction battery, if it's getting low. 'N' prevents any power from being taken off either motor.

In ACC or IG-ON, the HV battery is disconnected from the car. All electrical systems are powered directly and only from the 12V aux battery.

Every piece of equipment necessary to drive the car is powered up in IG-ON (LED on the power switch glows orange). This requires about 300-400W of power which will flatten the aux battery in less than an hour.

In ACC mode, the LED on the power switch is green. A limited set of equipment is powered on, so the power draw is lower and the battery will last longer. It's still not a particularly big battery, so try not to turn too much stuff on. With the brake pedal not pressed, each press of the power button goes from OFF > ACC > IG-ON > OFF.

The battery is relatively small because it doesn't have to start the engine. In fact the car will still boot up with very low 12V battery, but it will often behave strangely once started.

 

The ACC mode turns to off automatically after 1 hour on UK models to prevent the 12v battery going too low.

 

really? are you serious? i'm scared now!

 

Up, sorry!

Yesterday I got my car handwashed (left with 6 bars HV) and when arrived, the carwash guy returned me the car with 2 bars level, and lower MPG! It was in a below-grade-park, warm weather and ICE, and not more than 1 hour and 10min time between leave/pick...And they have a very small area for wash/park.
Since the time spent in washing normally does not pass 15-20min, my thoughts went to:
"Oh no! They left in on D during the washing!"

Can I judge that from my observations?

Or simply they ran the car for a mile in EV to park after washing?!

 

I suspect that the car was left in READY the whole time...

Not to worry.

Two bars is roughly the point at which the ICE comes online and
recharges the HV battery up to 3 or 4 bars and shuts down.

Many of the folks at parking lots, car washes, and repair shops,
etc, don't understand the Prius. They think that like a regular car,
if the ICE isn't running, the car/motor is shut down.

I once left my car at a repair shop for ~10 days. When I left it, it had
a near full tank of gas and 50.2 MPG lifetime over ~50K miles.

When I got it back the lifetime MPG reading was ~38.6, and the gas was
down to 3 pips

I think that the car was in READY all or a significant part of the whole 10 days!

 

I've just made an experience, after driving to the same SOC (6 bars), left it on Ready (with P) in my garage...and took about 15 minutes to drop 1 bar to SOC of 5 bars.
I think they left it in D, because time of washing was about those 15 min...

 

Yes, but the battery bars don't all represent the same amount of charge in the battery; bar 6 is around twice as big as the others. Additionally, because of hysteresis (which keeps the bars from flickering on and off if you're right near a border), there could be as much as four times the charge going from bar 6 to bar 5 (assuming you're right at the top edge just before it'd switch to 7 bars) as there is charge going from bar 5 to bar 4 (assuming you start where bar 6 ends as you discharge).

Specifically, if you start at bar 6, you can charge the battery up to 66.5% without hitting bar 7, then down to 55% before it switches to bar 5. But then the battery only has to drop to 52% to switch to bar 4.

Look at the image here. Basically, as the SoC changes, the display will keep showing you the same bar until you pass the end of that bar, and only then will it switch. So after it switches to bar 4 from dropping to 52%, you have to charge up to 54.5% to get bar 5 back.

Most likely, they left in in Ready and P the whole time; that's more than enough to discharge the battery, especially if you throw in moving the car around a couple times.

 

So you have a pokey little 12 volt or a huge big 200v battery that could power your house, but people still insist on using the 12 volt?

Just because you always listened to the radio in Acc mode in the past on non hybrid cars doesn't mean you have to now. With a hybrid you can sit in comfort with the a/c running and listen to the radio and barely use any fuel in an hour or more. Or you can leave the car in Acc mode, get hot and listen to the radio and run the risk of running the battery flat after 60 minutes.

Each to their own I guess.

 

Grumpy, I pretend there IS no other mode than READY. That works fine.

 

Hey... don't tell me that just listening to the radio on ACC mode with lights, console lights off, without power-hungry accessories in the 12V sockets will flatten fully charged 38 Ah AUX battery... Same sized battery is used to start normal, petrol Yaris and it doesn't get flatened within an hour of listening to the music.

I would not recommend to do it in IG-ON mode, which _will_ flatten this battery quite short. Prius should be used either ACC or READY modes.
IG-ON if you ask is quite useful if you had to record mileage for your records and don't want to start entire car (enginge starts immediately without 10s lag if outside temp is below freezing).

So if you are in well ventilated place, away from other people (not to put exhaust gases directly at somebody else or window) you can play radio on READY with A/C on. If not (like in the car cinema) better stick to ACC mode (first after POWER BTN without brake) with all lights off and 12V sockets empty.

 

Am I and I am not saying that. The 12v will be fairly well discharged after an hour and in a Yaris it will be charged up again pretty quickly. In the Prius the charging is slower so if you make a habit of short journeys and listen to the radio in Acc mode often, then yes you will run the battery down quicker.

Do it once in a blue moon and you'll have no problem.

 

You are right . Discharging it once will not be a problem. Do it few times between long trips the same. But doing it every day will surely destroy battery.

 

Glad this topic came up- today's my first day at work with the new Prius...
I usually spend my 30min lunch breaks sitting in my car catching up on current events via AM radio (WCBS 880 & WFAN 660). I'm hoping 30min in ACC mode with just the radio on and everything else off in a brand new car will not deplete the 12v battery?

 

this is a very confusing thread.