I'm curious. How do you know when stepping on the brake, when you stop regen and use the friction brakes, or when the friction brakes start absorbing energy along with regen? Also, a related question, I read on a site that the "B" position on my 2005 Prius transmission stick meant that it used regen braking. But the manual says "B" means it uses engine braking. I'm inclined to believe the manual.

Regenerative braking has nothing to do with the regular brakes. What it means in when whenever the acelerator pedal is released, the wheels drive the traction motor turning it into a generator, thus slowing the car because of the drag of the generator. The "B" on the gear stick is an engine brake, like a jake break on a semi truck. It spins the engine over to create drag, same as it's doing with the generator. But the compression is releaed from the engine so as not to create too much drag. If you drive with "B" engaged your gas milage will suffer because when the engine shuts down it goes into the brake mode , losing the benefit of coasting. "B" is best used to slow down the car for an anticipated stop. It saves the foot brakes and if if you know you have to stop anyway, engage the engine brake at a predetermined spot and coast on up to the stop. By coasting, you generate electricity thus saving the engine from having to run to charge the battery. If the generator is charging at max capacity, you would have put more recharge into the battery because it would have given you more coasting time.Anytime you can keep the engine from running, no matter how slight adds upto better gas milage. Accelerating briskly to cruising speed helps too.The little "leaves on wheels" that sometimes appear on the consumption display screen, represent 50 watt hours of free energy that was created by the regenerative braking system. It does not show the energy generated because the engine was required to run. The traction battery requires frequent charging because the amount of energy stored is limited and deep discharging is detrimental to battery life. It takes about a 1000 lbs of battery to equal the energy of one gallon of gas. A Prius battery weighs about 100 lbs so it can only furnish the energy of one tenth of a gallon of gas. RAY

On Tue, 8 Mar 2005 19:29:54 -0500 (EST), ray liptak

Thanks for the info. I wondered what the "B" was.

On Thu, 10 Mar 2005 19:28:56 -0800, Fred L. Curry

Thanks, but does the B mode enable engine breaking? How does it do that if the engine is single speed?

On Fri, 11 Mar 2005 18:16:31 -0800, Fred L. Curry

Fred, As long as the gear stick is in "B" and your foot is not on the gas pedal the engine brake works, it does not matter how fast the car is going. Try engaging it at any speed and leave it on until the car stops. You will notice the extra drag all the way down to zero mph. The effects of the engine brakes drag becomes more noticeable as mph decreases. While you're doing that, have the screen on that shows the diagram of the car with the wheels turning. On that screen you will notice that the green lines that are going from the wheels with the arrows pointing through the motor/generator to the battery are active all the way down untill the car stops. Whenever you see the situation described in the last sentence the car is expieriencing regenerative braking. Whether the car is in "B" or "D" and it is coasting along you will notice that it is in regeneration mode as long as youdon't press on the gas pedal. Engage cruise control while in the "D" selection, it will not engage while in "B", you will notice on the above mentioned screen, that if you are going down a grade steep enough, that you will have regeneration braking untill the car requires power to maintain the set speed. At the point of needing power you will notice on the screen the diagram will change from regeneration to activation of either the engine, the motor or both. For teh sake of clarifacation, keep in mind that usually a motor is electric and an engine is gas. Ray On Fri 03/11, Fred L. Curry <