remaining stationary while in "D"

Nope. First off, there's no clutch on the Prius, at least none that can be engaged or disengaged.

If you're hard off on the brake pedal (showing no arrows on the MFD), power is cut to the motor/generators anyway. I can see that by looking at # of amps going in/out of the HV battery when all the way on the brake vs. while in Park.

 

That is essentially correct but not mechanically correct.

The way the Prius drive train is designed, the electric motors and gas engine are always mechanically engaged to the wheels-- there is no clutch or anything to wear out by sitting in D for an extended period of time other than maybe the bearings in the gas engine if it's running or the bearings in the electric coolant pumps etc. Shifting to neutral simply electrically disconnects the electric motor-generators from the inverter so that no electricity can travel to or be generated from the motor-generators to anywhere else in the vehicle (HV battery, other motor-generator etc.). In this state, it also doesn't allow for starting or stopping the gas engine (because doing so requires using the electric motor-generators), charging the HV battery if the charge gets too low (which also requires using one or both of the motor-generators), or revving the gas engine if it was running when you shifted into neutral (because this would apply a motive force to the drive wheels that can't be countered by the electrically disconnected motor-generators). Basically in neutral, there is no motive force being applied to the drive wheels, and no way of causing any motive force to be applied to the drive wheels, even though the gas engine and electric motors are still mechanically engaged to the drive wheels, and even if the gas engine is actually running. This makes it behave more or less like a conventional vehicle in neutral, but it isn't mechanically similar to any conventional vehicle whether manual or automatic transmission.

I'd add a caveat though. There are times in my Prius when the HV battery is at a high state of charge where I notice that even with the brake pedal firmly depressed, I see a higher than normal amperage being drawn from the HV battery compared to shifting into neutral, but it's not very much difference at all (about an additional 150-400 watts). In fact it's much less than the A/C pump will draw while it's running (anywhere from about 800-2,000 watts depending on climate control settings and temperature differential). I suspect this is just a small load applied by the hybrid computer to gently draw the HV battery back down to a more usable charge level.

 

Neutral is required by law in the US, but is a very poor choice in the Prius in most settings. The Prius emulates Neutral by cutting all power to both Motor/Generators. With no power, the gas engine has nothing to push against and can't move the car. However, there is no way to charge the HV Battery, there is no way to start, or stop the gas engine. If you are in N below 40 MPH and coast to a speed above 45 MPH (exact numbers vary) there is a risk to the life of M/G1. Use N only when required and only in short time frames.

 

No, as other have said, there's no clutch to burn out and the power to the motors is cut (electrically) when your foot is on the brake pedal.

So the only disadvantage is that you need to hold your foot on the brake the whole time. If you were (for example) to apply the park brake and then remove your foot from the brake pedal (in D) then this would be undesirable, as it would be wastefully applying motor power against the park brake. Again it wouldn't damage anything, but it would waste battery power.

A similar situation can result if you apply too little pressure to the brake pedal. I find that once stopped, it is often possible for me to reduce the pressure on the brake pedal until the electric motors start providing some power to try to creep forward, yet the brake can still hold. So again you're wasting electrical power. This is particularly easy to do if you're pointing slightly uphill, so you do need to remember to provide enough pressure on the brake pedal to be sure that the electric motors are cut off. (BTW, the energy monitor screen shows you this with the arrows displayed so it's not difficult to check).

 

This is something I find strange with the Prius, why did Toyota not put a switch on the parking brake to remove drive when the parking brake is operated. This would resolve two problems:- having to keep your foot on the brake pedal while stationary in drive and being able to drive with the parking brake still on.

John (Britprius)

 

John, I'd assume that they didn't make the park brake cut the power so that people could use the park brake to assist preventing rolling on very steep hill starts.

 

If you put the car in N at the lights but left the a/c on, wouldn't you run the HV battery down lower than the two bars limit?

This could be dangerous if you've already spent some time in heavy traffic on a hot day.

Leave the car in D with your foot on the brake

 

GC I think you have have the situation confused.

If you put your foot on the brake you operate a switch that shuts down drive to MG2 "normal Prius operation" this is not neutral. Not pressing the pedal hard enough discharges the HV battery.

Now if you put a switch on the parking brake to do the same thing, when you are stuck in traffic you could apply the parking brake the result would be the same. You would still be in drive with no supply to MG2.

It is MG1 that starts the engine and that is not affected. The gen3 has hill start assist so this may be implemented on the gen3.

When I passed my driving test not using the parking brake in that situation was a fail.

John (Britprius)

 

This could easily be overcome by putting the switch on the ratchet pawl so that as soon as you touch the pedal to ease off the brake the switch is operated.

John (Britprius)

 

Yeah neutral is not a good idea, I'm certainly not suggesting using neutral.

If you are waiting a particularly long time however, then it's fine to use "P" mode (and the park brake if necessary). You just have to remember that you need to apply the foot to the brake when you're ready to get going, otherwise it wont shift from "P" to "D".

I made this mistake once the very first week I owned the Prius. I was waiting at a slow set of lights so I shifted to "P". I knew you needed your foot on the brake in order to get the Prius ready when first powered on, but I hadn't realized at that stage that you also needed the brake pedal to shift to from "P" to "D" at any time. I thought I was ready to quickly shift back to "D" and take off as soon as the lights changed, but I got stuck there in "P", right at the front of the queue with a stack of cars behind me. Eventually I figured it out, but by that time the lights where just changing back to amber so I took off leaving all the cars behind me stuck at the red light for another round. It was so embarrassing, I felt like such a dick.

 

I was writing it for others less informed to take note. I used to leave my car in Ready mode a lot of the time where it would switch on and off when required. Many people put an automatic in Neutral at the lights and whilst that's fine in a traditional car and could save fuel, it causes issues with a hybrid - as you already know.

And yeah, I've done that flustered dash to Drive after I've forgotten I'd put the car in Park. The guy behind must wonder what's going on when the brake lights flash a couple of times before I zoom off looking embarrassed.

 

I all ways use (p) at lights on read this stops the engine. Press the brake flick liver to drive and away dead simple that way you are not annoying the person behind that is staring at your brake lights for a long time i fined that very annoying.

 

But making it more likely they're smash into the back of you because they were half asleep and didn't realise you had stopped.