DarkStar
Well-known member
Were you rockin' ECO mode?gasmiser1 said:
Leaf regen vs Prius regen
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DaveinOlyWA
Well-known member
have to agree with the regen statement. the Prius regens much more than the Leaf does. in fact, regen on the Prius in many driving situations can account for nearly 100% of any braking situation. the Leaf does not.
when you watch the energy meter u will notice that the level of regen only increases slightly when in eco mode.
when you watch the energy meter u will notice that the level of regen only increases slightly when in eco mode.
Spies
Well-known member
I am curious how you came to this conclusion not that I am disagreeing with you. I have both a Leaf and a Prius myself and I am reluctant to come to the same conclusion if it is simply based on the display feed back that the Leaf and Prius gives to the driver.DaveinOlyWA said:
I apologize for taking this off topic and further discussion about regen would be better served in one of the other many threads about regen.
DaveinOlyWA
Well-known member
Spies said:
ummm dont quote me on this but i believe regen on 2010's go up to 80 kwh. my Leaf NEVER gets even half that much
gasmiser1
Well-known member
------------------------------------DarkStar said:
Yup, ECO mode the entire route. The only time I've used drive is to pull out of the garage up the driveway hill to the street.
DaveinOlyWA
Well-known member
Ok info from resident PriusChat stats expert.
Batt pack is 1.31 kwh with. 5 kwh usable. Defend up to 100 amps on 201 volt pack or about 20 kwh which is less than the Leaf max of 30?? Kwh but considering the huge size difference in battery packs I still have to say that the Leaf could be more aggressive with their regen
Batt pack is 1.31 kwh with. 5 kwh usable. Defend up to 100 amps on 201 volt pack or about 20 kwh which is less than the Leaf max of 30?? Kwh but considering the huge size difference in battery packs I still have to say that the Leaf could be more aggressive with their regen
Spies
Well-known member
I still don't know how much regeneration the Leaf can actually handle and it could be more or even less than the Prius.DaveinOlyWA said:
What I do want to point out is just because one needs to put their foot on the break pedal does not mean the Leaf is actually applying the physical breaks but is indeed using regeneration breaking.
When one simply says "regen" they could be talking about different things such as how much drag the vehicle applies to the car when neither the accelerator pedal or brake pedal is applied by way of regenerative breaking. This of course can be changed somewhat by using eco mode in the Leaf and b mode in the Prius. Or perhaps they are talking about how much energy the vehicle can recover though regenerative breaking no matter what drive mode is selected and how much the break pedal is used.
So when you say "more aggressive with their regen" do you mean the Leaf should be able to recover more energy when regenerative breaking or do you want the Leaf to have more drag by way of regenerative breaking when neither pedal is pressed or perhaps something completely different?
evnow
Well-known member
So, Prius can charge the battery at 15C during regen ?DaveinOlyWA said:
Anyway, when someone says Leaf should regen more - what does it mean ? Should Leaf slow down faster by capturing more power ... why ? A slow regen is likely more efficient than a faster regen.
DaveinOlyWA
Well-known member
No nothing like that. I want more control over the level of regen. The Prius allows me that control by feathering the brakes. The Leaf only slightly increases regen when hitting brakes while in Eco mode. I want to see a higher level attained that way. As far as the Eco level of regen while coasting. That is fine but we should be able to go much farther.
As far as the Prius. At max regen we could fully charge in 90 seconds to cover SOC. From 40-80%.
Obviouly the level of regen does vary with speed
As far as the Prius. At max regen we could fully charge in 90 seconds to cover SOC. From 40-80%.
Obviouly the level of regen does vary with speed
planet4ever
Well-known member
Can you explain that statement? If I am slowing to a stop light or going down hill, and the regen is not heavy enough to do the job, I'm going to be using friction brakes. That efficiency is 0%. Yes, I can see that at a higher C rate there is going to be more loss getting the energy into the battery. But surely the heat generated charging the battery is going to be less than the heat generated at the brakes.evnow said:
Put simply, heavier regen means less heat loss. Less heat loss means higher efficiency. No?
Ray
At least that number matches up with your earlier stated 20 kW max regen in the Prius and 0.5 kWh usable capacity - that's a charge rate of 15C - that is only pushing the batteries about 8 times harder than the maximum allowable charge rate that Nissan allows (~50 kW during quick charge at lower SOC).DaveinOlyWA said:
Would allowing another 30 kW of regen be useful on the Leaf? Sure would - but I suspect that Nissan thinks will wear the battery out too quickly, otherwise there's no reason to allow it. The motor / battery are capable of moving 80 kW+ when accelerating (though Nissan also cautions that frequent aggressive driving will also wear out the battery more quickly).
DaveinOlyWA
Well-known member
Any max value would be for short durations. Now if the Prius allows it on NiMH and the Leaf does not on Li, is there a difference in the capacity each type can take with minimal degradation?
its hard to argue with the Priuses already proven longevity concerning its battery management techniques
its hard to argue with the Priuses already proven longevity concerning its battery management techniques
I'm sure that if you use AESC's "high power" cells instead of their "high energy" cells and only used 50% capacity instead of 90%, you could push the Lithium battery even harder than the NiMH battery with the same life expectancy (10 years, 150k miles).DaveinOlyWA said:
In which case we'd be saying "Stupid Toyota - only 15C regen rate? Bah!" instead of "Stupid Nissan - only 1C regen rate? Bah!".
evnow
Well-known member
Sorry guys. I still don't get it.
Leaf does have variable regen. You regen more by pressing the brake harder. What we don't have is the ability to change the amount of regen for a particular amount of brake press.
So, is the ask that Leaf should regen more for a given amount of brake press ?
I've to come down a fairly steep hill everyday. If I use Eco I don't need to use the brake at all to control the speed. Sounds like enough regen to me ...
Ofcourse, if you know you need to stop at a point, it makes more sense to reduce the speed slowly rather than go at a high speed till the last few yards and brake hard.
Leaf does have variable regen. You regen more by pressing the brake harder. What we don't have is the ability to change the amount of regen for a particular amount of brake press.
So, is the ask that Leaf should regen more for a given amount of brake press ?
I've to come down a fairly steep hill everyday. If I use Eco I don't need to use the brake at all to control the speed. Sounds like enough regen to me ...
That is assuming the regen is constant. Not the case, only if you floor the break, Leaf will use friction brake exclusively. As you press the brake harder, it regens more, but after a point it starts including friction brakes. The idea is to slow down such that you use mostly the regen portion of the brake.planet4ever said:
Ofcourse, if you know you need to stop at a point, it makes more sense to reduce the speed slowly rather than go at a high speed till the last few yards and brake hard.
planet4ever
Well-known member
No, I wasn't assuming constant regen. I was assuming, based on what others here had said, that the maximum regen possible on the LEAF was significantly less than on the Prius.evnow said:
Thank you! I was getting worried. I'll now (try to) wait patiently for my car so I can see for myself.evnow said:
Ray
Ingineer
Well-known member
The Gen2 (NHW20) Prius tops out at about 21kw peak regen. The Leaf tops out at 30kW. The Leaf actually has more regen, but then again, it's a heavier car.
I find the ~20kW of regen in my Prius is more than adequate to stop the car with normal driving. Careful driving yields a bit more performance, and if you can stretch out your stops you get the most regen. This is because of the I2R losses. The battery charge efficiency goes up at lower rates.
Do not confuse the "simulated drag" regen, which I call "Pedal off" regen, with what happens when you hit the brake. The braking system first engages regen, and if pedal pressure is higher than what regen can handle alone, then the hydraulic brake modulator brings in some conventional friction braking to consume the difference.
Also, when the car gets below a certain low speed, the braking switches to friction, as regen is not able to hold the car once stopped.
-Phil
I find the ~20kW of regen in my Prius is more than adequate to stop the car with normal driving. Careful driving yields a bit more performance, and if you can stretch out your stops you get the most regen. This is because of the I2R losses. The battery charge efficiency goes up at lower rates.
Do not confuse the "simulated drag" regen, which I call "Pedal off" regen, with what happens when you hit the brake. The braking system first engages regen, and if pedal pressure is higher than what regen can handle alone, then the hydraulic brake modulator brings in some conventional friction braking to consume the difference.
Also, when the car gets below a certain low speed, the braking switches to friction, as regen is not able to hold the car once stopped.
-Phil
TLeaf
Well-known member
Another important thing to remember in this argument is that Nissan has programmed the Leaf to respond similarly to brake pressure no matter what the SOC of the car battery. In other words, at 90% SOC, light pressure on the brake might yield 1/5th the total possible regen but X amount of deceleration. Nissan had to make sure this same X amount of deceleration would be seen by applying the same amount of force on the brake even with a 20% SOC when the battery is looking to gobble up all the electrons it can take via full 30kW regen. I have little doubt that what you may feel is a "weak" regen is in some large measure Nissan's way of making sure that the car behaves identically no matter what the SOC. After all, it wouldn't do for a car with empty batteries to screetch to a halt via regen as soon as you ease off the gas yet have no regen effect at all when the car is at 100% SOC. That would feel like swapping back and forth from an exhaust-brake-equipped ICE with massive engine-braking forces to an electric car with no regen capabilities.
I personally had gotten quite used to the backwards throttle twist regen action on my Vectrix scooter, so I can certainly understand the desire for a user modulated regen, but to its detriment such a system lets you continuously pump regen back into the battery no matter what the SOC, severely shortening battery life for those not knowledgeable about a batteries' limitations to accept charge when near capacity and the associated battery heating. For now I'll content myself with popping in and out of ECO as needed...
I personally had gotten quite used to the backwards throttle twist regen action on my Vectrix scooter, so I can certainly understand the desire for a user modulated regen, but to its detriment such a system lets you continuously pump regen back into the battery no matter what the SOC, severely shortening battery life for those not knowledgeable about a batteries' limitations to accept charge when near capacity and the associated battery heating. For now I'll content myself with popping in and out of ECO as needed...
LakeLeaf
Well-known member
DarkStar said:
Remember, on the Prius it isn't the regen that really slows the car down on steep downhills. It's the engine braking. The Prius will continue to hold its speed even after the battery is completely topped off. The LEAF has no engine braking as it has no engine.
planet4ever
Well-known member
Come on, we've been around this argument several times already. The Prius does not use engine braking on a hill until the battery is full. There's a steep mountain pass I sometimes go down. The engine is silent until near the bottom, but when the battery is full the engine starts roaring very loudly. And when the next graph bar shows up (99mpg, of course) it has lots of regen cars stacked in it.
Ray
Ray
Ingineer
Well-known member
LakeLeaf said:
On the Prius this is not true, unless the battery is full, or you choose the "B" position on the shifter. The Prius does just like the Leaf; it simulates engine drag with regen when you take your foot off, but if you feather the pedal slightly it's effectively neutral and will coast. As you begin to hit the brake, the computer increases regen until it's at 21kW on the Prius, or 30kW on the Leaf, then brings in the friction brakes to "fill the gap".
Panic or really sudden stops (detected by the brake ECU by pedal velocity) automatically skip regen and bring in ABS only.
The Battery ECU on the Leaf will limit charge depending on battery SOC and temperature, so there are indeed times when regen will be less than 30kW. For instance, if you start at the top of a hill with a fully charge battery, you will not get any regen.
Also, just to be clear, "Engine braking" is indeed possible in an EV like the Leaf; all that has to happen is DC injection by the inverter. This will convert kinetic energy into heat in the motor windings. I don't think the Leaf does this, but it could be implemented as an emergency backup if the hydraulic braking system were to fail.
-Phil