At what temp is decreased regen braking noticeable

[MightyHawk]

I think we are talking past each other.

I am referring to the instantaneous energy exceeding the regen ability of the battery, whereas you are talking about the accumulated energy that the battery can hold. If the instantaneous energy being offered to the battery exceeds the regen ability, the semi will gain speed, even if the battery is not full.

But as the article noted, resistive coils can be used in that case. And with that, I am going to stop beating this dead horse.

 

[Pavlo_Y]

Weird, never had regen dots before, with limited regen, but had them today. Mid-50s. Battery at 75%. Drove about 25 miles, and the dots never disappeared, and I could feel that the regen was not fully there. I'm on the latest software 32.11.1

Same here I'm on the latest software 32.11.1 and had car since April (where we had some temperatures in 60s before) but never seen limited regen until yesterday (it was around 60F outside).

 

[AlanSubie4Life]

As mentioned elsewhere in this thread, regen limiting can occur regardless of temperature and state of charge. To protect the battery, it does not allow continuous regen for too long a period at moderate states of charge. Presumably at a very low state of charge there would be no limitations at all (no dependence on regen history) - but I have not had an opportunity to test that case.

On Monday in 70 degree weather at the top of the hill, with 80 degrees at the bottom, with a 2500-foot descent, after having been driving for an hour at 50-60mph, with about 70% SOC, I watched the regen dots (starting with none) gradually accumulate as I went down the hill. It never got to the point where it was a problem and I had to use the brakes - I was able to limit my speed to 55 mph down the hill just by lifting the accelerator. Obviously the increasing regen dots were not due to the increasing SoC. It just had to do with the regen history.

It will be interesting to see how this works on the Semi - though of course for emergencies presumably they could bypass the battery protection phenomenon described above, if it became necessary.

 

[abasile]

Limited regeneration is self fixing on cold mornings, starting from the top of a mountain.

As you depend, the motors waste heat will warm the battery and regeneration will begin, far before brake fade will become an issue.

Really a well thought out system. Works most all the time.

We live at 6100' elevation and routinely make a descent to 1200' over 16 miles, with speeds in the ballpark of +/- 45 mph. Regen limitations have not been a problem, even during the coldest winter weather, thanks to the active thermal management of the battery pack. It does help some if we time our charging to end shortly before leaving the mountain. We also try to avoid charging above about 85%, and we brake early rather than requiring rapid deceleration. Besides the Model 3, even our older Model S still does fine at regen down the mountain. Our older Nissan LEAF, on the other hand, is terrible with regen unless the battery is mostly empty.

 

[mswlogo]

I saw Regen "Dots" in the middle of Summer in New England. Supposedly AWD puts out more regen so it may apply limiting sooner than RWD with the same LR Battery. High 80's during the day, 60's at night. Was garaged overnight.

But with those few limited regen dots, which could take a while to go away, had no impact in how the car felt. You don't hit MAX regen that often.

As far efficiency goes, just ignore modestly limited regen. Coasting on the highway is MORE efficient than Regen is.
Yes, around town unlimited regen will be more efficient.

You're goal isn't regen, you're goal is driving without using the brake pedal and quickly/instinctively adapting to changes in regen.

Now, when severe regen limiting happens it can be a little startling, but don't let it be and don't be afraid to use the brakes if you need to.

Now where OP is located he might see a bit more regen.

BTW, my new Volt has Low and High Regen on the Shifter. On the Highway it's more efficient to use Low Regen (D on Shifter). Around town it's more efficient to use High Regen (L on Shifter). It's kind of neat to be able to flip it so easily. There is also a paddle on the wheel that momentarily puts the car in High Regen mode.

Good point on state of charge. 90% SOC will see quite a bit more limited Regen than 70% or 80%.

 

[Big Earl]

I think we are talking past each other.

I am referring to the instantaneous energy exceeding the regen ability of the battery, whereas you are talking about the accumulated energy that the battery can hold. If the instantaneous energy being offered to the battery exceeds the regen ability, the semi will gain speed, even if the battery is not full.

But as the article noted, resistive coils can be used in that case. And with that, I am going to stop beating this dead horse.

The Semi’s 600 kWh battery should be able to take up to 480 kW of regen for a pretty good length of time. That’s more than double the power of a typical Jake Brake system on a diesel.

 

[Phlier]

The Semi’s 600 kWh battery should be able to take up to 480 kW of regen for a pretty good length of time. That’s more than double the power of a typical Jake Brake system on a diesel.

I think that the semi truck might end up being a great application of Maxwell’s ultra capacitors. A huge bank of ultra capacitors can, unlike a battery, accept current as fast as it can give it out. So instead of just throwing away excess electricity into a resistor bank that is then turned into waste heat, the ultra capacitors can soak in a lot of that current, then slowly feed it back into the battery at a rate the battery can take.

Of course, once you’ve hit the regen limit of both battery and capacitor banks, you could still have a resistor bank to turn any additional current into heat.

IMO, we will be seeing huge Maxwell ultra caps in the semi truck. And possibly in our cars at some point.

 

[ajdelange]

Resistor banks are a thing of the past. You now just turn the motors' torque settings down so they don't absorb torque from the road (it's the mirror to turning the torque setting down when you don't need as much power to maintain speed).

To return to the OP question: Assuming you are nominally charged (90%) you will see regen limitation start to kick in when the battery gets cold soaked to somewhere around 50 °F.