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Discussion in 'Model S: Driving Dynamics' started by redline0316, Mar 5, 2014.
Is it not possible to make the regen more aggressive than the two available settings?
No, there are only two settings.
If I understand the OP's question, he's asking WHY there isn't more aggressive regen. There is no reason I know of that the motor couldn't supply more than 60kW when operated as a generator, thus creating a stronger regen braking force. But Tesla has chosen to limit regen to 60kW, max, presumably for one or more of the following reasons.
1) It's too hard on the battery pack and would shorten pack life.
2) It's not considered desirable in terms of safety and/or driving dynamics. 60kW is already too aggressive in situations where there is limited tire grip due to road conditions.
3) The inverter/electronics can't handle it (this is speculation on my part).
It is 80% of 2), 15% of 1) and 5% of 3)
I started a thread with some musings on this a while back: Firmware feature request - Option for Regen > 60 kW?
Above 60 might cause too much wear on the tires. It's akin to hard braking all the time.
I would wonder if it would be a saftey issue, imagine you are in unfamiliar territory and come up on a tight turn, when you let off the accelerator it would be like pulling the parking brake on an older car, great for moonshiner turns, but not something I wouldnt want to do in wet weather in a Tesla. (Or any car)
It shouldn't have to do with battery health. Our batteries can accept 120 kW charging and can output 320 kW at peak. Putting 60 kW back into the battery via regen seems pretty tame by comparison.
this would be correct.
exactly how high-strung do you want this car?!?
120kW when they are at a very low SOC. Doesn't the power level taper fairly quickly?
I don't think you need to go above 60 kW power to get a more aggressive feel to the regen.
Change the regen curve.
As the car slows, the regen also backs off and won't bring the car to a stop.
Test drive the i3. I would guess the regen never reaches 60 kW yet it feels more aggressive.
The regen will bring you to a complete stop, yet is not jarring. It feels very smooth and natural.
Now, the regen in the Model S is the best, most natural feeling regen I have experienced other than the i3. But I think the i3 really nailed it.
Are you saying regen braking is applied to only one wheel?
I was under the impression that it applied to a pair of wheels.
Presumably if the car needs to taper the regen charge, it will do so automatically by limiting your regen. It already does this in cold weather and when your battery is at 100%.
Yes, the back wheels. Are you saying "old cars" only applied parking brake to one wheel?
It's probably a combination of factors... Most likely it isn't the batteries, but remember that the generated power from regen is initially A/C and must be rectified. There may be some limits in the power electronics (inverter/rectifier), although I really don't know.
My personal opinion is that 60 kW seems like an appropriate amount of regen; that more could be designed, but it would negatively impact the user experience. I really don't want it to be any more seat-jarring than it is.
Yes, 85kWh models can accept 120kW when they are fairly empty.
And they accept more than 60kW from SC only when SOC is under ~60%.
I don't have SC charging curve for 60kWh models at hand, I'd guess SC power goes under 60kW around 40% SOC.
To maximize range and be more efficient, drive the car in a way that you need regen as little as possible. Higher regen rates don't make the car more efficient.
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Agreed, it would be awesome if that could be done with a new firmware update.
Wish it was more as well, brought the car to a stop and took into account traction control for slippery situations
Just as an FYI, the way I understand the regen algorithm to work (Standard Regen selected) is this: the software attempts to provide 0.10g of longitudinal deceleration, with a 60kW maximum (or lower, depending on battery SOC and temperature). Somewhere down around 5mph, the regen feathers out completely.
only when not working properly, note the "old cars" in quotes. And yes in my youth I saw enough cars that only locked one wheel when the parking/emergency brake was on that I thought that was by design until I read otherwise on the internet decades later (and apparently I still flip/flop remembering how this works)