Question for Hybrid regenerative braking

idk how it works either. full ev's have more powerful regen and can bring the car to a full stop. because of toyotas built in creep, it would be counterproductive i suppose. maybe more expensive too?

 

The limiting factor isn't the motor, it's the battery.
A battery cell can only accept so much electricity at once before it starts overheating or suffer damage. On top of that, there is a finite amount of electricity the cell can hold. A hybrid sized battery simply doesn't have the capacity to take in all the energy the motor can generate bringing the car to a complete.

A BEV battery has a lot more cells, so the car can stop with regen braking. Or you can add a bank of resistors like a locomotive to convert the excess electricity from braking into heat. Even then, a motor isn't the best way to get a car at creeping speeds to completely stop. I'm guessing the motor speed has dropped below the point at which it generates electricity, thus losing braking force, which could be what brake torque refers too.

Adding a smaller motor or transmission to downshift at those speed so the required braking force will generate energy is a possible way to kept around that, though they won't help with a full battery. Those don't address the issue that a motor is a poor way to hold the stopped car in place. At that point, the car needs a system to determine which way it will roll, so it can send energy to the motor to counteract that motion.

Friction brakes are a cheap, easy solution to that. Plus, they will be on the car for emergency use and parking anyway. so go ahead and use them for the final stop. It was already possible to go 100k miles on a set of brake pads with a gen2 Prius.

 

Actually you were right. The regen capability has a lot of stopping power and is the primary braking at most speeds unless:

1. Your hybrid battery is maxed out already. This is rare unless you are coming down a mountain pass.

or

2. You are seriously hard braking. This still gets significant regen braking plus power hydraulic braking for maximum sudden or hard braking.

or

3. Your brake by wire "brake booster" and or integrated regen control goes bad. You not only lose regen braking but you can lose power assist of the hydraulic braking. In that case you are left with "failsafe" manual hydraulic braking with increased stopping distances.

Regen braking is so effective that many do not ever replace brake pads or rotors. At 285,000 miles my four rotors and two sets of front pads are original and still legal.

At 250,000 miles I had one rear hub start making noise so both rear hubs were changed and the oem pads in the rear were swapped while in there. The rear pads would have otherwise remained except for the hub replacement.

That length of time on original brake parts does not happen if the hydraulic brakes are used much. Obviously I and others anticipate stops and try not to routinely brake hard at the last minute. Others do and wear their brakes faster.

Maximum use of regen braking also provides epa or higher mpg.

 

You must be doing something wrong.
In summer if I want I can get 35mpg in an RX450HL in stop & go traffic and it is a 2.2 ton big fat SUV rated at only 29 mpg city. The brake pads only engage at around 6mph, last few feet before stopping. Again that’s with a careful foot on the pedal.
I think there might be a hole in your gas tank.

 

I think it was a design decision as well - they just did not want to have some kind of one pedal drive. I drove hybrids with smaller ev motors that could do that in regular D mode.

e.g. daihatsu rocky (toyota raize) has "smart pedal" mode for D

 

Something is off. I only saw numbers that low in a 2005 on the highway. Going up big hills, or doing over 75mph.

 

Theory816 has an undisclosed year Highlander hybrid with 200k miles and is posting all over the forum. He is trying to get a Prius or FJ Cruiser brake pump to work in his Highlander that has a failed brake booster.

No telling what the Highlander's hv battery condition is or what his driving style is like in a large hybrid that may have achieved 28 mpg back in the day.

 

Thanks, that explains rather a lot.

 

okay that’s not too bad. I thought you managed to achieve below 30 mpg in a Prius and wondering how was that possible.
But I’d still be worried about the battery condition if city mileage is worse than highway.

 

Those are conditions where an excellent hv battery really helps you out. What year is the Highlander?

By the way the least you could do is change your signature from
2010 Prius to 20xx Highlander Hybrid V6. Highlander in the title of your threads and posts would help. Misrepresenting yourself is not cool.

 

The Other Cars forum isn't a bad choice, and for even more general stuff Fred's House of Pancakes remains ready to serve.

Both of those forums get a lot of traffic and have many sub-forums. Enjoy!