Having previously owned a Honda Civic Hybrid II, I am familiar with how the regen braking works, but more importantly how much regen is being fed back into the batteries by the regen guage on the Honda.

The Prius on the other hand just tells you that regen is occuring, but not by how much.

Is it the same as the Honda's in that - coasting downhill gives you 'X' amount, but by gently putting your foot on the brake pedal you can increase this amount...just before the mechanical brakes come into play?

I can't feel the transition from regen braking to mechanical braking in the Prius. Is there a way of telling what the "tipping point" is?

Also, does the top battery bar ever fill?

...and while I'm at it. Yes, I now believe that the Prius is an easier car to achieve low fuel consumption with than the Honda. I really had to work hard to get anywhere near the figures that Honda was quoting.

Hi,
There are at least two brake hacks that determine the transition between mechanical and electrical braking.

You can top off the battery bar by descending a very tall hill at high speed using modest braking or by doing a 'forced charge' at a stand-still. You hold the brake with one foot and floor the accelerator. This is a Toyota diagnostic procedure and instrumentation shows this puts no undue stress on any of the hybrid vehicle systems. When the battery is fully charged, the control computers turn off the engine.

Forced charging is used at hybrid rally events or when showing off your car to skeptics. With a maximum traction charge on an engine and transmission warmed up car, the MPG performance is initially very impressive. It is also useful for maximum acceleration testing. However, the overall efficiency is terrible because of the fuel burned just charging the batteries.

Bob Wilson

After April 3, use e-mail to contact me:

It's difficult indeed to tell how much regen braking there is available, but from those with "Canview" devices, it appears there is a lot more than you might think. I'm told, unless you are trying to "stand the car on its' nose", you are using regen. only until you get the speed below 7 miles per hour. Below 7 MPH it's friction braking only. Both regen and friction braking are used under heavy "non-panic" braking. If you suddenly slam on the brakes it's friction only.

If you are descending a long hill pressing the brake pedal will indeed regenerate more (the amount of regen without the brake pedal depressed is there to simulate engine braking).

You will fill the top bar when descending a very long hill - say 2 miles of very steep hill or longer if not so steep. When you do shortly thereafter you will feel the regen braking go away. I find it noticeable because the car seems to want to take off down the hill. Braking will then be friction only. This is why there is the "B" position on the shift lever. It uses the engine to "waste" energy and slow the car. Once you have full green bars you will notice the car using the battery/electric a lot more to get back the "headroom" it wants. Full green is 80% charged, BTW. The car will not let you get any more charge after that until it brings the charge level down.

Pearl is a
2007 Driftwood Pearl Prius
Package "B" (everything but leather, nav, and rear camera)

So basically, so far, I have never fully charged (80%) the batteries!!

Still...this is a really fun car to own and drive.

Thanks for the excellent explanation guys.

So it looks like the Prius can regen much more than the HCH II? I have always wondered how the Prius can do better than the HCH. I mean the ICE is better in the Honda, the aerodynamics about the same. Sure there is a larger electric motor/battery but using electricity is inherently inefficient if you have to burn a gas motor to get it. But if you can regen more than that would help. Now - if you DWB - it doesn't matter. In my driving, I can almost go without using friction brakes (except the first stop sign from my house).

And yes - I realize the Prius is far better in stop and crawl situations but I almost never do that.

I get about 60 mpg in my HCH II but it drops to 50 if I am with the wife on a trip going 70+. I always have figured that a Prius would be about the same. We will be looking for another car soon but I am holding out for something better (more efficient) to replace the 96 civic.

No, it hasn't been proven that the Prius regens more than the Civic Hybrid.

BTW, the HCH-II uses the friction brakes throughout, but at varying levels. I would think that that is for safety reasons, the friction brakes being ready as a backup in case the regen fails.

I think it's funny that this topic starts with an anecdote about the Prius being easier to achieve high fuel efficiency, only to be supplanted by wacky, model-specific techniques. At what point does the Prius stop being a car and become a gadget?

When you get the keys.

Bob Wilson

After April 3, use e-mail to contact me:

I only rented the Prius for a couple of days last year, but I could definitely feel when the regen braking ceded to conventional braking. There is a "give" in the brake pedal when it switches over at moderate braking. I experience something similar with the Civic.
Also keep in mind the Prius has a much more powerful motor than the HCH, which allows it to generate more elecricity when in regen mode.

It just "seemed" to me that to get the economy figures that Honda were quoting, I really had to work had. But with the Prius, I was almost achieving the stated economy figures on the first tank!

I think that the Prius gives you more options. In our country we have the "Stealth" button. So I can force the Prius to stay in all electric mode...basically up to about 60MPH.

This means that it is easier to take full advantage of all that stored kintetic energy, which the Honda seems to want to dispense as it sees fit.....and....stopping the ICE in the Prius is easy, in the Honda it was a lot harder.

Also depends on the weather! Prius seems to get better mileage when it is hot, especially when you keep the set temperature low on either car. On the other hand, many Prius owners report poor (less than 40 MPG) mileage in winter, whereas it is easy getting good mileage on the HCH when it is cold. This is probably due to the Prius having to run the ICE more to generate heat for efficiency and cabin heat in winter.