Question for you real techies - I like to efficiently use my regenerative braking. Proof of that is that I have 107K miles on my 2008 and havn't had a brake job yet. Referring to my 2012, on the Hybrid System Indicator Screen, there is a CHG bar. The harder you brake, the more the bar fills from right to left. When the bar is full (when braking harder) do the brake shoes offer the balance of braking power needed. Does the CHG display indicate that much accuracy? Thanks!
From my understanding, the brakes do not engage until the bar is full. Anything before that is all regenerative.
Once the bar is full, friction brakes are on. If you brake lightly at high speeds, the CHG bar will fill up very quickly --> the regenerative braking can only take so much.
The higher the speed(MPH) is when the regenerative braking is applied the higher the charging rate. For example, regenerative braking gets more energy (Kwh) from braking at 40 mph than at 20 mph. During any regenerative braking session, there is a fixed overhead energy loss when changing the mechanical energy back to electrical energy for the HV batteries - from what I understand the regeneratively braking process is more energy efficient when the HSI display has moved left pass the 1/2 point(mid-point) of the CHG bar but has not yet touched the far left end of the CHG bar ( because that would trigger the hydraulic/friction brakes).
I wonder how many miles I can get from my Prius' brakes. I had my first brake job done on my 2002 Camry, at 140K miles. New pads plus rotor resurface (rotors were well in thickness spec). The brake shop commented I must have been very easy on the brakes. I expect the Prius would do better under my watch
I wonder how much more efficient it is past the 1/2 way mark? Just nominally, or quite a bit? Where did you hear/read this at?
I'm not sure. I 'm just parroting (hopefully correctly ) the postings I've read on this topic over the past few years on cleanmpg.com/priuschat.com/yahoo! groups/websites. For example, I remember reading online a (?car & driver?) review of the 2010 Prius describing how a Toyota engineer accelerated really fast and then press the brakes really hard so he could recharge the HV battery SOC back to 8 bars. A while back Wayne Gerdes did a Fuel Efficency(FE) Challenge to demostrate how a 2010 Prius could achieve way over 65mpg (which initially was very dissappointing , because he had achieved much better on a gen2 Prius ) - to do this Gerdes recharge the Prius HV battery up to 8 bar before starting (as well as pre warmed up the ICE) before doing his FE Challenge circuit loop. On Cleanmpg.com - Wayne responded to my inquiry/posting and describe how to recharge the HV battery while the Prius is standing still. I experimented and validated this procedure - however, recharging the HV battery by running the ICE while the car is standing still causes the overall MPG to drop in much the same way as when the Prius automatically recharges the HV battery while it is stuck in traffic jam. So I found such techniques only useful for demostrations purposes only. FWIW I remember reading that regenerative braking can capture between 30% to 50% of the energy in braking - the rest is lost in heat/friction - I can't remember the source though . I've been warned by other hypermilers several times to stay away from the EV mode. For hybrid hypermilers the cleanmpg.com mantra is - while regenerative braking during a stop is more efficient than regenerative braking while the car is still in motion (e.g. going downhill using B) - it is even more energy efficient if the driver does not have to use regenerative braking at all - and a hypermiler should primarily focus on conserving his/her momentum. The most energy efficient way that I have found to recharge the Prius NiMh battery go to a very high hill and from the top of that hill accelerate to a high speed at the crown (top 1/4) of that hill and for the rest of that downhill segment apply the regenerative brakes as the Prius goes downhill. It turns out that the longer the downhill and the faster the Prius's initial speed is - the more charge you can potentially generate and store into the HV battery. While driving down a mountainside in PA - my 2010 Prius HV battery SOC has gotten as high as 78% ( 8 bars). When the SOC is at eight bars the Prius does strange things, e.g. . Cruise control won't start until the SOC drops back down to 68% and the electric motor is on almost all the time... The Prius is happier when its SOC is betwen 50% to 68%...
I was way impressed to see my 2012 use regen brakes automatically to keep my speed down when using cruise on a long downhill grade, then to beat it all, the engine brake kicked in when regen braking wouldn't hold him back!
Prius brakes rust badly and that triggers service long before they need replacing. At least in salt infested areas. Some GII owners built devices to try to detect when friction braking started. Nice that it's built in now.
It's not just the rotors. In the GII the rear -drum- brakes got quite "messy" due to corrosion. The parts other than the drum. If I drove Pearl in the rain, the next morning I had the "scraping" noise as the pads cleaned off the rotors. (backing out of the garage friction brakes are used as I am below about 7 MPH). I haven't noticed that with Pearl S so far. My FJ Cruiser squeals loudly in the same situation. Pads are like new, rotors are also like new. Rust never sleeps!
