Dumb question: why does my prius have 3 brakes!

1. That's the normal foot brake to be used in normal driving situations

2. That's the "hand" brake.

3. That's not a brake, it's the "park lock" that all automatic transmissions have. It does assist the "hand" brake but it must only be applied when car the already fully stopped. Actually you don't ever really need to activate anyway as the prius will automatically activate it when you turn the power off.

The key difference between 2 and 3 is that "2" is a regular friction brake (it actually just applies the normal brakes on the rear wheels) while "3" is transmission locking mechanism.

 

1. Normal service brake, all other cars have one.
2. Park brake, all other cars have one.
3. Park position for the transmission, all other automatic transmissions have this.

What was your prius specific question?

 

1. The brake next to the accelerator is your standard brake.

2. The brake closer to the drivers door side is the emergency brake.

3. [P] is the parking brake. It is basically analogous to the parking break in a regular car's gear shift.

Turning on the car requires the following steps.

1. Step on the Brake (the one next to the accelerator) and press Power.
2. Release the emergency brake with your opposite foot (with your foot still on pedal.)
3. Shift to Reverse or Drive.

To turn off the car:

1. Step on the brake. Press [P]. Again, this is like shifting the gear to Park on a regular car. A lot of people say this step isn't necessary because when you press Power it automatically puts the car in Park (you'll see the green square light up on the button). But I think it's a good habit to do this step.
2. Press the emergency brake.
3. Power off.

 

Well to help understand the park-lock "P" versus normal brakes think of it like this. If you've ever ridden a bicycle then the normal brakes are the rubber blocks that rub against the rims and the "equivalent" of [P] would be to jam a broomstick between the spokes. That's why you can only do it when fully stopped.

 

""" P """" comes in handy when you stop at the drive in window of a fast food joint or the bank and want to keep the car going, but don't want to move.
When you want to get going again, just hit the brake pedal and throw the 'stick' into """ D '''. (drive)

 

And the reason you might want to keep your car running at that point is because it's 25 degrees out and you want the car to warm up so you can get some heat inside of it.

 

There is one more brake you didn't list, the B position on the shifter is engine braking.
This is like down shifting in a manual car except it wont give you better acceleration. You can use engine braking (B position) to retard the car when descending a long steep hill. You will hear the engine spinning when in B mode and the cruise control will not work.
If you also apply the brake pedal in B mode the engine will spin even faster.

Only use B mode when the battery will be full before you reach the bottom of the hill, otherwise it is better to brake gently, as this recharges the battery rather than waste all the energy.

To take the car out of B mode, move the shifter to D position for a moment, you can do this any time.

Cheers, welcome to Prius Chat, and enjoy your new car.

 

25 degrees here is just perfect!

 

Username appropriately applied by asking these questions...love it! But my wife would say otherwise...

 

Or if your sitting listening to the radio waiting for your kids to get out of swim practice. Better "ready" than "accessory"

 

I wish we would get our terms right!

The pedal on the left side of the foot well is the "Parking brake". An "emergency brake" can be easily modulated. Usually found with an arm you pull up on, or a "T" handle you pull out. The "Parking brake" applies the "friction brakes" on the rear wheels, just like any other car.

"P" is park (an automatic transmission term). It locks the wheels mechanically -at the "transmission" output-, and is either on fully or off so is not actually a "brake", but more correctly a "stop". If you force the wheels to turn while in park you can cause damage immediately. It takes a lot of force to cause damage. Usually the tires will skid before anything breaks. Before putting the car in "P" or before turning it off, you -should- apply the parking brake. This will reduce the forces on the "park mechanism" if the car tries to roll. Note that the Prius is smarter than many of us. If you apply "P" (or "R") while moving the car will not go to "P" (or "R"), but instead goes to "N".

There are actually two other braking mechanisms, the actual "friction brakes", and regenerative braking.

Friction brakes we are all familiar with. Note that the Prius has anti-lock brakes, so wheel lockup is controlled.

Regenerative braking is new to most people (except Prius drivers, of course ). Most of the time when you apply force to the brake pedal (the one just to the left of the accelerator pedal) at "normal" speed (non-panic) and "normal" force (non-panic) you are mostly using regenerative braking, until the car slows below a certain speed (call it 10 MPH for argument). It can apply a surprisingly (to me, at least) significant amount of braking.

If you apply a lot of force on the brake pedal the brake system will transition to full friction braking.

If you rapidly press on the brake pedal (slam on the brakes) you go directly to friction braking, and a "braking assist" system also comes into play. It's a good idea to test this so -you- know what to expect. First, remove or secure all items -IN- the car, especially you and any passengers! Yup, you will be stopping hard enough to cause things to fly about in the car. Then, in a deserted parking lot or on a deserted road, do a "panic stop". You will be shocked at how fast the Prius can stop! I suspect repeated "testing" will cause abnormal wear, but trying it out a few times is a "good thing" (tm), as it teaches -you- what to expect when that -other- idiot pulls a genius move in front of you.

 

"Emergency brake" and "parking brake" are not normally terms we use in the UK. We normally just call it the handbrake due to the vast majority of cars having manual transmissions with hand-operated parking brakes.

I usually shift to neutral and let the parking brake ('handbrake') take up the slack before pressing "P".

"P" on an automatic is basically the equivalent of leaving the car in first or reverse on a manual transmission, with the engine off, rather than leaving it in neutral - it's an extra thing to prevent rolling away should the parking brake fail. On the Prius, there's an extra difference because the car can't charge the battery in neutral, when the car is Ready, so you don't want to leave it in neutral for any length of time: however it can charge in "P". It automatically applies the parking lock when you turn the car off.

 

It should be noted that in an automatic transmission, it's NOT a great idea to rely on the parking pawl (PARK position of the transmission, or in the Prius, the P button) to hold the car. One should always use the parking brake. Sometimes, with too much stress, that little metal pin that locks the transmission in park can break, and it's an expensive ordeal to repair it.

 

Do note that in the Prius the "park pawl" often referred to is not a pin or a pawl at all. It's the only sliding "gear" in the HSD, and it slides into a mate bolted to the housing. It's pretty strong! I have heard of cars dragged out of garages in "P" with no damage, other than to the owners nerves! It's actually more complex than that, but you get the idea.

But even so, it's a good idea to take care of it. It can be replaced without disassembling the HSD housing, though if destroyed I would be worried about pieces falling inside!

 

Really? I would expect the engine to be able to run the generator as well when in B mode. And actually be able to charge the battery faster than breaking alone (in which case only the motor is charging the battery).
I haven't checked in a while, but I am pretty sure that when in B the battery does get charged.

 

You get more energy recapture by lightly braking in D than by using B. B simply dumps a heap of enegy via the engine through the radiator and exhaust pipe mainly.

This is easy to confirm in a Gen III Prius, watch the energy monitor, when about to slow down and select B mode, see how much regen you get, now repeat but use the foot brake wiithout using B mode to slow and watch the regen almost hit the end of the energy monitor. You can modulate the regen with the brake while monitoring it on the energy monitor.