Dynamic Braking

[fbacher]

Are there any guidelines on how much of your braking energy goes to recharge the battery versus heat?

When I am coasting along and see a stop sign or red light, when should I start applying the brakes? I assume that a hard stop is a big waste. I assume a light stop mostly charges the battery. So if I am a block or two away should I slowly slow down to a crawl or what?

[hjon71]

<div class='quotetop'>QUOTE(Frank Feuerbacher @ Jan 22 2007, 10:17 PM) [snapback]379290[/snapback]</div>

Are there any guidelines on how much of your braking energy goes to recharge the battery versus heat?

When I am coasting along and see a stop sign or red light, when should I start applying the brakes? I assume that a hard stop is a big waste. I assume a light stop mostly charges the battery. So if I am a block or two away should I slowly slow down to a crawl or what?
[/b]

1. A hard stop is always bad no matter what you drive.
2. Anticipating stops and getting off the gas is good no matter what you drive.
3. Your MPG and your brake pad life will increase no matter what you drive.
On the prius, I think you're just as well off coasting as lightly braking. Besides, if you start slowing down soon enough for a traffic light, it might turn to green before you have to brake to a stop.

[Beryl Octet]

<div class='quotetop'>QUOTE(Frank Feuerbacher @ Jan 22 2007, 10:17 PM) [snapback]379290[/snapback]</div>

Are there any guidelines on how much of your braking energy goes to recharge the battery versus heat?

When I am coasting along and see a stop sign or red light, when should I start applying the brakes? I assume that a hard stop is a big waste. I assume a light stop mostly charges the battery. So if I am a block or two away should I slowly slow down to a crawl or what?
[/b]

Ina hard stop, you can feel the friction brakes take over. As others have posted, smooth and gradual is best. Two blocks away seems like it might be overkill though.

[efusco]

This'll give you some basic non-tech info:
http://privatenrg.com/#100kBrakePads (scroll down a bit after the page loads)
Here's some technical data points:
http://www.vassfamily.net/ToyotaPriu...veffindex.html
and
http://www.vassfamily.net/ToyotaPrius/CAN/...ndex.html\

and (finally)

http://www.vassfamily.net/ToyotaPrius/CAN/brindex.html
Bottom line is that the earlier you start slowing down the better. If you must wait you want moderate brake pressure...when you have the tools to see it you're shooting for 60amps regen for optimal charge rate.

[JimboK]

One of the techniques of some of the master "hypermilers" is called DWB -- driving without brakes. Here is its decription from CleanMPG.com:
<blockquote>"In its simplest form, you drive as if you do not have brakes. If you have degraded or no brakes for whatever reason, you will increase buffers in traffic like you may never have considered previously. In heavy traffic and traffic jam conditions, this will allow you to maintain some speed before throwing away energy to heating up the pads/shoes. With larger buffers comes the ability to maintain a very slow speed while most others are in a stop and go jam. You can use this in any traffic tie up or heavy congestion. Pro’s include higher FE, less wear on the ICE and braking systems, and easier on your mental state. Con’s include drivers around may continuously fill your buffers and thus you will again back off to recreate them. It may actually tax your mental state depending on your aggressiveness."</blockquote>
I apply this technique whenever practical as I approach stop signs and red lights, guided by traffic conditions (I try to balance courtesy and maximum fuel economy).

[fbacher]

<div class='quotetop'>QUOTE(Beryl Octet @ Jan 22 2007, 10:01 PM) [snapback]379322[/snapback]</div>

Ina hard stop, you can feel the friction brakes take over. As others have posted, smooth and gradual is best. Two blocks away seems like it might be overkill though.
[/b]

Thank you for the data.

If I am in heavy, stop-n-go traffic (highway at 5pm that is crawling at 1-20 mph) do I maximize use of battery + coasting or do I use the engine as much as possible, or do I just crank up the toons and relax ?

[efusco]

<div class='quotetop'>QUOTE(Frank Feuerbacher @ Jan 23 2007, 11:28 AM) [snapback]379569[/snapback]</div>

Thank you for the data.

If I am in heavy, stop-n-go traffic (highway at 5pm that is crawling at 1-20 mph) do I maximize use of battery + coasting or do I use the engine as much as possible, or do I just crank up the toons and relax ? [/b]

I tend to maximize battery use when possible in those situation if the movement is fairly slow. If traffic suddenly speeds up go ahead and kick int he ICE. But, after a relatively short time you're going to drain down the battery to the point that you're going to start the ICE every time you move and there'll be little you can do to maximize anything...just be happy you have a care that shuts off the ICE when you're not moving.

[hobbit]

Depends on how fast you're going. On some of the secondary highways
they've got the "RED signals ahead" signs that actually work right,
i.e. start flashing the RED long before the actual light goes yellow.
This is the time to start that beautiful long less-than-50-amps
gentle regen glide, that happily sucks up all that kinetic energy
all the way down to the light but still moving about 10 mph when it
goes green and traffic clears out. Never hits the binders at all.
.
On the other hand, there's often the "sixty-to-zero surprise" where
they don't care about helping traffic time itself and set up the
light controllers like they were on any random suburban streetcorner
and on a fixed-time cycle instead of using the traffic sensors like
they should. A lot of townie proles aren't paid to think.
.
_H*