I coudln't find the correct thread section to post this question so I'll leave it here. Recently my brake system failed so I had to learn more about how it all works. I still don't know how it all works because it's pretty complicated. But I did learn something interesting that changed the way I viewed the regenerative braking. All this time, I thought that when you coast, it's the regen motor that stops the car until the very few last feet. Turns out, the regen motor barely has any torque to stop the vehicle. Turns out, the ABS brakes kicks in to help slow the car at all times. That got me thinking, if the regen motor does help bring to car to a halt but it can't fully because of low braking torque, why not add several regen motors to bring that braking torque up and bring the regenerative power up?
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.
Ok that makes a bit more sense. Another thing I noticed is that highway driving at 55mph seems to give the best mpg. Driving around town in stop and go even with hyper miling I can only get 20mpg but highway is a good 32mpg. That's crazy.
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.
When my highlander hybrid was in "new" condition(I've owned it from new) the most mpg I could from it was 32mpg, which was the rated mpg. On the screen hybrid drive meter, I can see that city driving I am getting less mpgs but highway its higher. Right now, I am getting a healthy 28mpg even though my ABS system is in failsafe mode.
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.
Sorry for the confusion with vehicle titling. Thing is, the other subs arn't getting much traffic and there's no place for me to ask general questions. The highlander is a 2007 and suprisingly, I still have alot of faith in the batteries' reliability, although it's lost about 2-3 charge bars and discharges quicker than I recall from new. The ball bearings, motor, and EV batteries have all been bullet proof for me in a car with over 200k miles.
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!
