What happens during light pedal pressure braking?

I Finally Understand Hybrid Regenerative Braking | PriusChat

The second post in that thread is a video that may help.

 

Why would it have to be anything as coarse as the ways you're suggesting? This is all done by software in computers: the one that controls the braking, the one that controls the battery and knows how much regen current it is able to accept from moment to moment, and the one that coordinates between the two, and they all communicate in real time.

Ultimately, the answer to your "what happens" question is "this":



(with some further discussion over here to clarify what's being shown there).

Efforts to simplify it even more than that would be overlooking that thing Einstein may have said.

-Chap

 

#searchfeaturedeletemod

 

people with scan gauges have reported light caliper application with the beginning of braking, along with heavy regen, and the the two switching places as more deal pressure is applied.

most efficient method is to anticipate stopping as early as possible, and using glide and/or foot off the gas pedal regen as long as possible.

 

Those graphs, and the further discussion I linked to, did not come from "an ideal world", they came from the Toyota New Car Features manual for the Prius, which is the one where they tell you how it actually works. No should about it. It also explains exactly how the hydraulic failsafe system fits in, if that interests you.

It is important to look at the right NCF for your Prius generation; there were significant brake system changes between all the first three generations. (I'm not saying there weren't for the 4th gen, I just haven't boned up on that brake system yet.)

-Chap

 

I believe that the light caliper is ultra light and is done so that the caliper can be applied as soon as it is needed. The light caliper application must not cause much friction/wear. If it did we would not get the extremely long life out of our brake pads that we do.

 

A member here once replied to a reply of mine saying "that's an assumption." If the comment above aint then I don't know what is

 

I think he is confusing conversion losses, like when the ICE charges the battery and recapturing energy through regenerative braking. If you don't recapture energy when slowing down, you lose it, so it is not inefficient in the way that that term is usually used.

 

Energy will never be completely 100% utilized when driving against weather, tires, terrain, brake pads & etc.

Slightest brake pedal pressure, regen will always engage before brake pads engages rotor even if your speeding/gliding down hill the grapevine in southern California, with the help of techsteam. If not for that, Prius would have been complete failure.

 

That's an assumption.

In this case, an assumption that depends on Prius generation (check the 2004 NCF manual for the changes in control logic between Gen 1 and Gen 2, for example).

-Chap

 

I've struggled with finding the best way to charge the traction battery, so forgive me if this is a dumb question. Are you saying that gliding to a stop light is better for regen compared to using the brake? If so, I've been doing this incorrectly.

 

regen is not that efficient. the more you can anticipate stopping, no energy used or restored, the more efficient you will be. pulse and glide. of course, traffic does not always allow for this.

 

Let's say the traffic conditions allow for either a glide to a stop sign vs riding the brakes? The regen on the dashboard indicates that riding the brakes is better and that's all I have to go on. Is that misleading? Are you saying that braking really doesn't do much compared to other ways to replenish the traction battery?

 

I would say that the braking does a lot, but may not be the best use of the kinetic energy the moving car has. There will always be heat losses in regeneration. So, the farther you can coast without any regeneration, the better ... UNLESS ... If you coast too close to the place you have to stop and end up braking harder than you would have otherwise, you may be wasting your coasting gains. The ultimate would be to coast with no regen down to a stop. But who's got the patience or the perfect timing for that!

Still, compared to just using friction brakes like a gasser, regenerative braking is sheer wizardry. So, I just do my best to plan ahead so I brake as gently as traffic and practicality permit and praise the Lord that engineers have finally built something I've been wanting for at least 45 years.

 

let's say your battery is 50% full as you see a stop light way off in the distance. if you let off the gas at the right time and press on it enough to get into glide mode, and coast up to the light, you arrive with 50%

if you use too much gas/electric, so that the battery goes somewhere below 50%, and have to use the brakes/regen to stop at the light, the battery will not recover to 50%, there's no free lunch.

it's like going up and down a hill. you lose more than you get back.