Regenerative Braking

I can tell you that with agressive braking, that is when the mechanical brakes come into play. Coasting or gentle braking regenerates the maximum power, without using the mechanical brakes.

I would like to have one of the more experienced posters expand on what they might know as far as the actual threshold between gentle braking and harder braking when the mechanical brakes kick in.

Also, would appreciate if someone can confirm, as I understand, gentle braking down a hill will regenerate power, but use of the B position of the shifter uses the ICE to brake. Therefore, the B should not be used unless agressive braking requiring the mechanical brakes is needed to maintain speed on a hill, which seems like it would be very rarely. Am I correct?

 

Don't stop aggressively. Start braking as soon as possible. Don't do it too early so drivers behind you get annoyed.

If you have EV button installed, engage and accelerate as hard as you can before HSD cancel out of EV mode and resume normally. Remember the "G" you feel from the pull on battery alone. That is how much power the battery can absorb back. So, brake around that "G" and you should be able to recover probably 90% of the energy and you may see more green bars.

Edit: I have yet to confirm the charge rate is the same as the discharge rate.

 

<div class='quotetop'>QUOTE(NoMoShocks @ Mar 11 2007, 01:36 PM) [snapback]403860[/snapback]</div>

Yes I'd like to see that information in terms of % braking as displayed by CAN-View (or probably ScanGauge).
Can we have agressive braking defined in terms of such a percentage?

P.S. I just noted that my time stamp is screwed up. See the 12:51 PM at the top of the page (may be changed now that I'm editing). It's 1:54 PM according to my computer, and I see other posts indicating it's just before 2:00 PM. What gives?

Well, that's strange. After exiting and looking it says 1:51 PM now.
Dave M.

 

Very aggressive braking, in the form of a panic stop, will cause the brake system to abandon regen braking and switch to friction brakes. For best regen, brake early with modest pressure. As you increase the brake pressure, the current levels rise, which causes less efficient charging of the battery. The most efficient braking is no braking at all; coast as much as possible, but be safe and don't annoy other drivers.

The regen system drops out at about 7 mph, after which the friction brakes take over.

Tom

 

It's always most efficient (as with any car) to drive with moderation: Don't baby it, but don't push it either. I've seen over 100 amps going into the battery, so it can take a pretty fair amount of regen.

B mode uses engine braking to slow the car, like using low gear on a manual transmission, or jake brakes on a semi. The only time you should use B mode is when an extended downhill will rise the SOC of the battery as high as the computer will permit (about 80% of capacity, or something more than "full" on the screen icon) because once the battery will accept no more charge, then friction braking is used. B takes some of that job off the brakes and puts it on the engine. Friction brakes and engine compression braking both waste energy by dissipating it as heat, so you only want to do that when the battery is full -- or, in the case of friction braking, when you need to make a very quick stop.

It's really difficult to put into words how hard you can step on the brakes and still have 100% regerative braking, especially since that will depend on factors like SOC and battery temperature. I think the best description is "moderate." Neither too gentle nor too hard.

 

I think this should be placed on the FAQ list somewhere.

http://vassfamily.net/ToyotaPrius/CAN/brindex.html
Attila's experiment shows pedal value 17 (13% on CAN-view) is the best.

Ken@Japan

 

<div class='quotetop'>QUOTE(ken1784 @ Mar 11 2007, 11:10 PM) [snapback]404016[/snapback]</div>

Ahhhh. 13 for us Can-View owners. I was wondering how he was getting a 22 sec stopping time with 17. I was stopping a lot quicker when I used 17. I'll try 13 now that I know this.

That brings up a question. How do you know its 13? Am I missing a conversion somewhere?

 

<div class='quotetop'>QUOTE(theforce @ Mar 12 2007, 12:15 PM) [snapback]404019[/snapback]</div>

Attila's brake pedal value 17 is the raw number on CAN and the max is 127.
CAN-view shows it 0-100%, so 17/127=0.13 or 13%.

Ken@Japan

 

<div class='quotetop'>QUOTE(ken1784 @ Mar 12 2007, 01:40 AM) [snapback]404066[/snapback]</div>

I see now. Thanks.

 

So, the 17 out of 127 can also be displayed on the ScanGuage III ?

 

Question: when I brake too hard, is regenerative breaking still occuring (in addition to normal friction braking)? Or does the system stop regenerative breaking and just switches over to friction breaking?

If it is additive, then, as a layman, I should just moderately break and not worry too much about maximizing regeneration (if it needs to use the break pads, so be it - just can't be helped). If however, they are not additive - then I have to be careful to avoid friction breaking.

 

<div class='quotetop'>QUOTE(John in LB @ Mar 12 2007, 06:16 AM) [snapback]404126[/snapback]</div>

Friction braking comes into play only in a panic stop, at very low speeds, or in some special cases involving loss of traction. Brake normally and don't worry about it.

Tom

 

<div class='quotetop'>QUOTE(NoMoShocks @ Mar 12 2007, 04:46 PM) [snapback]404099[/snapback]</div>

In Japan, there is no ScanGuage III nor ScanGuage II users.
I think ScanGuage II does not show the brake pedal value.

Ken@Japan

 

<div class='quotetop'>QUOTE(ken1784 @ Mar 12 2007, 03:57 PM) [snapback]404335[/snapback]</div>

Nor is there a ScanGauge III user in the U.S., unless I've missed something. Version II is the latest as far as I know. And it doesn't provide any data on braking and regen.