Regen - Cold? Why don't they like each other?

[Garlan Garner]

Ok. So my P3D+ has 120 miles of range left.

Outside temp = 24 F

Why doesn't regen work?


Why am I asking? Because I went to a Super Charger and the it started out charging at a rate of 64Kwh. So....if the battery can charge at 64kWh - why doesn't regen work? I have no expertise in this area however i don't believe that Regen is creating 64Kwh.

Both charging the battery and Regen is a form of charging the battery pack.

 

[outdoors]

You have been a member for 971 days and average 8.50 posts per day over that period. I would like to think you're asking for the benefit of the greater family of new Tesla owners.

Supercharging and regenerative braking are two completely different methods of recharging the battery. Both are carefully controlled by the battery management system of the car. All I know is that after 25k in miles I have had no range loss. I will let Tesla take care of the battery while I continue to drive. Don't have much other time than to do that. Just drive.

This question was just asked in another forum which you commented in. Why create a new one? Moderator please merge.

 

[ewoodrick]

Cold weather plays havoc with batteries. I remember taking a camera on a ski trip and I started to take photos at the top, the camera would not turn on. Got to the bottom to debug it and it turned on. Took a sec to remember that the batteries were too cold, they just didn't work.
Next time, I kept the camera inside my jacket and it worked fine.

Regen breaking hooks the motor to the battery. Generally, the batteries will accept the current and that creates the regen pressure. When they are cold, they can't accept it, so nothing creates the regen pressure.

Now, I will admit that Tesla seems to be pretty obnoxious with their regen restrictions, other EVs don't to seem to have the same extremes.

 

[SMAlset]

As I recall ICE car batteries the last time we had to buy one came in different price ranges based on their cold cranking power. Not that this is here or there.

 

[mswlogo]

Ok. So my P3D+ has 120 miles of range left.

Outside temp = 24 F

Why doesn't regen work?


Why am I asking? Because I went to a Super Charger and the it started out charging at a rate of 64Kwh. So....if the battery can charge at 64kWh - why doesn't regen work? I have no expertise in this area however i don't believe that Regen is creating 64Kwh.

Both charging the battery and Regen is a form of charging the battery pack.

I think that’s a fair question. But I must say that never happens to me. So your saying you have a lot of dots and it immediately went to 65kw. Or was it 65 kw after 10 minutes.

Also what was your charge rate in mph? Some of those kw might be going towards heating the battery.

I’ve also read though that the regen is fairly high kw. They are short high bursts of energy. They are so short generally they better be high watts.

 

[Garlan Garner]

You have been a member for 971 days and average 8.50 posts per day over that period. I would like to think you're asking for the benefit of the greater family of new Tesla owners.

Supercharging and regenerative braking are two completely different methods of recharging the battery. Both are carefully controlled by the battery management system of the car. All I know is that after 25k in miles I have had no range loss. I will let Tesla take care of the battery while I continue to drive. Don't have much other time than to do that. Just drive.

This question was just asked in another forum which you commented in. Why create a new one? Moderator please merge.

What? What difference does it make how many posts I have or how long I've been here? Really?

 

[eli_]

Probably they are more concerned with cell lifespan impact from routine regen braking versus the occasional supercharging and it could have more strict limits for that reason. Or perhaps it expends more energy to heat the pack before supercharging, while when driving it's less likely to spend energy on active heating. It's a bunch of trade-offs.

From the factory mode screenshot the Model 3 has a 46.9 kW regen limit, but that could be because of SoC or temperature.

 

[jsmay311]

What? What difference does it make how many posts I have or how long I've been here? Really?

Well... after so many posts, you could at least learn the difference between kW and kWh by now.

J/k. But in seriousness, I'm also perplexed by the described behavior. It doesn't make any sense to me.

There was really no regen right before you started Supercharging and then it started charging at 64kW? This doesn't seem to jibe with all the instances of slow Supercharging during drives in the cold that I've read about previously.
Is Regen set to "Standard"?

 

[Garlan Garner]

Well... after so many posts, you could at least learn the difference between kW and kWh by now.

J/k. But in seriousness, I'm also perplexed by the described behavior. It doesn't make any sense to me.

There was really no regen right before you started Supercharging and then it started charging at 64kW? This doesn't seem to jibe with all the instances of slow Supercharging during drives in the cold that I've read about previously.
Is Regen set to "Standard"?

Yes....
There was no regen right before I started Supercharging...then it started supercharging at 64kw. Indeed. That's what's happening.

Yes. Regen is set to standard.

 

[JulienW]

[speculation]The amount of power needed to heat the batteries to a temperature to except a regen charge outweighs the benefit of the small amount of regen but when you plug into a SC a large amount of the initial power goes into heating them up to except the faster charge rate.[/speculation]

 

[LMichel]

It was described to me (from a Tesla Service Person) that a supercharger can provide significant energy to heat the battery and power the thermal management system at the same time. "No matter what, the battery will not accept energy unless it is between the low and high temperature" was his initial answer.
So, a huge portion of that 64kW is really being used to get to temperature fast. Then the charging starts. But the charging screen just shows the whole thing as charging, not some for heating and some for charging. Destination chargers and your wall outlet, etc. just don't have the available potential to heat things up so quickly.

When the battery is cold (below temperature) regen can't charge the battery - because of that - "No matter what...." rule.
After some driving, the battery is warm from both discharging and a thermal management system is 'catching up'. Yes, range mode seems to have some affect on these settings?

BUT, I've always maintained that the two different "feels" of regen could cause for a dangerous situation. The proof is how Tesla even warns you with yellow dotted lines and triangle in the display. Even they admit that diving your Tesla is somehow different than typical?
I posted many months ago that I never understood why Tesla engineers didn't take up some of the frunk to have a small 5kWh battery with its own (simpler) management system and different chemistry and kept near 50% SOC. Let that battery take the regen "dump load" when things are cold in the main battery. Once things warm up, divert to normal and discharge any residual from the dump load back into the main as well. I'm told that engineers could have even accepted the regen energy and diverted it to the thermal system to heat things a little faster, but they argued that things were already complex enough.

That last part just doesn't make sense to me: 'Gee, doing the extra complexity is too much, lets just leave the car a little dangerous for 20 minutes or so'. It's like saying "Gee, an extra motor, switches, sensors, linkage and wipers? Naaa, too complex, lets just have the view be a little more dangerous when it rains - we'll light up a moisture sensor instead"!

NOW, I'm dying to know; How many days have I been a member and how many posts per day?? LOL

 

[jsmay311]

Pics/vid or it didn’t happen.

This would be an awesome capability to quickly warm up the battery if true, but sadly other people’s (better documented) descriptions of supercharging with cold batteries is nothing like what’s being described here.