I have found at any given speed 70 / 50/ 30mph ect. If I have my foot off the gas and I am getting the green arrows to the battery "regen braking" ,That if I just ever so lightly touch the Gas peddle it shows I am still running the green arrows only " Charging the Battery", But I can feel the car braking a little less.Feels almost like I go into glide mode/ Yes I know the difference between Gliding " No Arrows" and Regen with Green arrows to the battery. So can the car still be charging but rolling with less drag by doing this, Or is my screen not accurate? PS you can feel this effect the most when going down a steep hill around 50 to 70 mph.
Sure, regen is a continuum. You start to see the green arrows at around 7 amps...you can regen up to around 100 amps before it kicks out to friction brakes.
49er, Evan, are you guys saying that you can determine the amount of regen you're getting using the go-pedal ??!! And pardon my surprise, you can actually find/hold minute go-pedal positions "inside" the regen range. Holy cow! I hope the following question is close enough to the original post not to be seen as a hijack attempt. With regard to the amount of regen you can recover, does it make a difference if you brake easily all the way down a long hill, or use a true "no arrow" glide to pick up speed/momentum and then brake smartly near the end/bottom? (I'm thinking of a long, steepish hill where I can get up to 50+ MPH in a glide, with a stop sign at the bottom. With the exception of this one hill on my commute, I am typically oblivious to regen; it might happen but I don't try to get it.) I see the regen question as the flip side, and potentially of equal importance, of this recent thread: http://priuschat.com/forums/fuel-ec...ccelerate-fast-slow.html?highlight=accelerate
Yes, that is the short answer to the above question. Regenerative braking is a continuum, from max regen to zero. The amount of regeneration is controlled by the accelerator pedal and the brake pedal. When you release the accelerator pedal, the Prius applies a small amount of regenerative braking to simulate engine drag as would occur in a normal car. Pressing lightly on the accelerator pedal causes this simulated drag to reduce. Pressing more removes the simulated drag entirely. Any more pressure after that and you start adding power to the electric motor. Likewise, when you press the brake pedal it tells the Prius to use more regenerative braking. The harder you press, the more it regenerates. There are limits from the electrical and battery capacities, and traction, but other than that it is entirely related to brake pedal pressure. If you exceed the regenerative limit, the friction brakes take over, just as they do at low speed. Tom
Well, that's not exactly what I was talking about...I was speaking directly to the question of controlling the amount of regen with the brake pedal. But yes, to a degree you can control the amount of regen during coasting. For instance, most of the time when you lift your foot off the 'go-pedal' you'll see about 14 amps of regen while you coast with foot off brake and accelerator. you can feather the accelerator gently to reduce the drag in fractional amounts or to a full glide (usually with -3 to -6 amps). If you google or search this site for "60 Amp Braking" you'll find a detailed and technical discussion of this very question. My answer is that it depends. 60 amps has been found to be the rate of regen, with the prius, that maximizes the regeneration you'll gain. So it's theoretically best to brake such that you'll regen exactly 60 amps from the point brakes are applied until you get to 7mph (where regen drops out). That said, this is a variable thing....if you have to keep your foot on the 'go pedal' an extra 1/4 mile to get to the spot where you'd need to apply the 60 amp ideal braking then you're probably not energy ahead...it would be better to go into a glide earlier and then apply 60 amp braking later and for a shorter time for net energy saved. I'd say that moderate brake pressure is what you want to shoot for...if you apply firm braking late you risk accidently dropping out of regen completely and you'll be braking less efficiently.
Our 400h SUV (maybe the hyhi also?) has a gauge showing amp regen / discharge rate ... not that I need any more gauges to distract me. It IS kind of cool stepping hard on the brakes to watch regen from front & rear electric motors (as stated above ... not trying to hyjack here). Perhaps the Gen III Prius will include this kind of moniter, instead of a simple green line (yellow on the Lexus). Does either the v1, v2, v3 CAN-view show regen / discharge?
49er, Evan, et al, Ok, if I understand what's been posted, there are at least two discrete levels of regen in the "blue arrow" range of the go pedal. (And I assume that you found this using a CAN reader.) This is good to know for modulating deceleration against distance for gliding to a stop. I don't have a CAN reader but I do have a ScanGauge II. I believe that on one of the recent SG threads, the codes for displaying HV battery volts and amps via the XGauge feature were posted. It sounds like I should be coding in for HV Amps. Lets say I get lucky and it works, and I then set the HV(A)mp readout to be displayed as a gauge. This hill I've spoken about is, aside from the ambient temps, the make or break element of my morning commute. If I handle it well, it can mean the difference between 48 and 60 MPG. To set up for it, I've got to get my blue bars down to 4 by using the HV battery, yellow arrows, over a set of small undulations and through stops at a few traffic lights. As I crest the hill I could switch the SG from say RPMs to HVA(mps) and shoot for max regen as I descend. I'm looking for 8 green bars at the stop/90 deg left turn at the bottom. With 8 green bars I can then work gliding and Stealth Mode (under 40 MPH) to go almost 2 miles without using the ICE, this on a trip of 13.2 miles total. At this point in the trip, I'd revert to RPMs as I enter a 50 MPH highway with 5 or 6 bars remaining where I use a combo of Pulse & Glide and SuperHiway Mode (SHM) to cover the next 8 miles. Maxing out MPGs through all this is dependant on cresting the top of that hill at a very low SOC, 4 bars, and sitting at the bottom of the hill with 7/8 bars. What do you think? By using the SG to get max regen starting from an intentionally low SOC, I'm thinking I just might be able to pull it off consistently. Many thanks for the "60 Amp Braking lead." That's where I'm going next.
I guess I'd have to say that 'no' there are not 2 discrete levels. We might be thinking the same thing, but to 'discrete' means you see either 14 amps or 3 amps with no in-between range. What I've tried to convey is that it's infinitely variable depending upon your ability to feather the accelerator or brake.
Be aware as well that regen charging may not be as efficient at 60 Amps as at, say, 15 Amps. Also, at 60 Amps you will quickly heat up the battery. You would have perhaps 30 sec. of 60 Amp charging before the battery started to get warm (it's not really a "big" battery) and the system "throttled down" the charging to help regulate the battery temp. As well as all that to think of, running on the battery, charge and discharge, is less efficient than running on the ICE. That is, charging and then discharging the battery rather than using the ICE for that power is less efficient. There have been figures thrown about on this inefficiency and I don't recall them at this time. Sorry. Of course charging the battery with energy you would have "wasted" as brake heat is more efficient. All I'm saying is don't get too enthusiastic about electric propulsion as it's not the most efficient mode most of the time with the Prius.
Actually 60 amps is the most efficient. This was derived by Attila Vass I think a full 30 seconds of 60 amp braking would exceed the capacity of the OEM battery. Absolutely.
