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Limited regen on a cold day?

Today is under 20F in Wash.DC, and I noticed a broken yellow line on the regeneration meter of the instrument screen. The car wouldn't slow down much when I took my foot off the "gas" pedal, which was really confusing. The regen setting was set to Standard as always. At first, the yellow line was around 15 kW regen, and then it jumped to 30+ kW after 10 miles of driving. Does anyone know how regen gets limited as a function of outside temperature? How long does it take the car to warm up the batteries to the point where regen goes back to max and the yellow line goes away? I only drove 12 miles to get to work and that definitely wasn't enough...

Regen is limited when the battery is cold or when it's a full charge. This is normal, and the line goes away when the battery warms up.

And some of your "lost" range comes back too!

Epley & HansJ are correct. Recently at -10F there was no regen at all until the battery was warmed some (I did get a notice there was no regen when that occured)

When the mobile app is available, when you pre-heat the car, the battery will start warming up too, so it will at least partially if not fully alleviate the lack of regen when you start driving.

was about 10 miles for me too today to get regen fully up. Philly area was between 15 and 20F this morning and evening. was what I expected.

Isn't this dangerous? S owners are getting used to the car reponding to pedal inputs in a certain way, and many are commenting on learning single-foot driving most of the time, using regen as a primary brake. I wonder if TM will be forced to rethink its software limitation on regen while warming up after a spate of rear-end accidents and attention from sleazy lawyers... "yes, your honor, the brakes function differently depending on outside temperature." Really? Really?

jemartin

Take a look at the Chicago forum and then "cold weather issues". We've been talking about is since it has been very cold the past few days, down to -2.

@Pungoteague_Dave, I get what you're saying, but it hasn't been a problem for me since the dotted yellow line is so noticeable on the guage. I haven't found it at all difficult to be conscious about the limited regen when starting a drive inthe cold. And still, at least since we're all coming from driving ICE cars around, I still have the instinct that if it feels like I'm not slowing at a rate that is good enough for whatever is ahead, that I need to put my foot on the brake.

je, kevin, noel;
You can make it a non-issue by charging overnight at an amperage level insufficient to quite fill the car by morning. Thus it will still be charging then, and you will start off with full power and regen.

The Leaf is exactly the same, but with 4 regen "bubbles" instead of the dashed line. At the temperatures we have now (5degF or so) I frequently have no regen at all for quite a while, even though the battery is only charged to 80%. I have no problem at all adjusting to this.

All very useful info. Thanks.
Brian H: I'll try your trick tonight. There is another post somewhere that describes using a low charging rate overnight to hit the non-peak electricity period, which usually starts after midnight.

je;
Yes, that just puts more/most of your time into the discount period.

If you don't really need any or much mileage, plugging in to 120V achieves the same thing as low amperage. If there's a chance you'll hit Full, set to Range Charge (Max Range) and let it eat a little into that.

Brian - I will try that tonight - thanks for the tip.
I also just got 4.2 installed this morning and it added a warning message to the dash when regen is off.

Heh. Just responded to a similar comment on another thread.

Anyhow, should work. Let us know how it goes!

I found the absence of regen braking very disconcerting on the recent cold days here in Chicago. Even if the braking isn't going to charge the battery because it's too cold, I'd appreciate the option of having the car drive the same as it usually does (i.e., with simulated regen braking). Folks have mentioned that it's very strange to drive an ICE rental car after driving with regen braking, and I agree. While I am, of course, capable of being cautious and adjusting my driving and braking habits, it would be nice to be able to just get used to how the Tesla performs in that regard and not have to adjust based on the weather. Trickle charging all day isn't really an option for me when I'm parked for work. I guess the app will be the solution in the absence of simulated regen braking, but even that will take some planning, as sometimes I don't know for sure that I'll be driving in 30 minutes.

I agree, the regen braking should slow the car the same way regardless of weather condition. I was caught off guard by this over the weekend. It's not hard to adjust to, but with something as important as braking the car should stop in a consistent, predictable way.

I currently drive a Chevy Volt, and there is no issue at all with regen and cold weather. It drives exactly the same at any temperature. Why can't Tesla manage the same thing?

Like the Model S, the Volt has two regen settings, normal-ICE-feel and stronger-EV-feel. The Volt setup is actually better, because you can easily switch settings on the fly, simply by shifting from D to L. I normally run in L, but sometimes on long freeway drives, or on long gentle downhills, I switch to D. Nice to have the option. I hope Tesla eventually makes the regen adjustable on the fly, with multiple settings.

I really don't have concerns about the regen in cold weather. I am notified when it is occuring. For me it's a non-issue.

I find it very disconcerting when regen doesn't respond as expected due to a cold battery. It's a wart on what is otherwise a superior, consistent driving experience.

I don't get my car for 3-4 weeks, but I know when I drive a rental I roll through the first few stop signs because I'm accustomed to my BMW brakes. I've even almost rear-ended a car on the very first braking situation. Driving a car you're accustomed to is almost like breathing - you really don't have to concentrate on it. Change in what you're used to is bad.

There is a simple solution for all of this - we need a mobile app that lets us set the cabin environment and pre-warm the battery, whether the car is plugged in or not. The app needs to let the user set the desired "ready time" so the user can activate it well in advance and let the software decide (based on the ambient, cabin and current battery temperatures) when to do what in order to minimize the power consumed. All of the data and control is available now, and this is less complicated than sending a vessel to the ISS!

C'mon TM, Giterdone!

For those who are thinking that heating the cabin will warm the batteries enough to turn regen on, I believe you are going to be disappointed as the current draw to warm the cabin is no where near enough to heat the batteries sufficiently. And if it was then we start going down the path where everyone is complaining they have no range left because the pre-heating took all the range away.

Having driven the Roadster for several years now I have learned it is not hard to adjust to no regen. Disappointing that no battery charge is happening as you lose range but I think it is the best solution Tesla will be able to come up with. It adds complexity (and weight) to have some other item draw current just to keep the regen feel the same. And the dash does let you know how much regen that you have available via the dotted line and/or the "no regen available" warning.

I have found the implementation very intuitive as the regen keeps getting less and less as the battery gets colder. Once regen is off the next thing that happens is that top acceleration starts to be limited. After having the car sit in single digit temps for ove 10 hours I came out to a car that was limited to less than 160kw and close to the 80 mark. Still plenty of power and I just had to be ready to use the brakes. What I find refreshing is that the car warms up much faster than any ICE car I have ever had. Good trade off in my opinion.

Long term ideas for keeping the regen braking feel constant when the battery is not able to absorb enough current when cold: (1) modulate the hydraulic brakes as the accelerator pedal is lifted. (2) Use the regen current to warm up the battery quicker.

@Theresa - If you heat the battery eventually while driving (which restores range and regen), isn't that the same as heating it before you start driving? Isn't the amount of energy used to warm a battery from A temp to B temp the same regardless of whether the car is moving or not?

With smart pre-heating (meaning you define a "ready time" and the software calculates the optimum heating start time) I don't think there is a difference in the energy used either way. (Actually it is easier to warm a stationary object in a cold environment because the convection loss is higher with air moving relative to the car.)

I think this is an easy engineering problem that has an easy fix - use the app to preheat the battery optimally based on the user-selected ready time. It's no less energy efficient to do this, and safer to boot. If people don't want to do this for some reason, just don't it.

@Theresa, it is my understanding that pre-heating the cabin will also activates battery warming. In other words, we're not saying that the battery warms up simply because it is in use to run the HVAC. Of course, I could be wrong, but the 'Your battery is col' message that can pop up in the UI seems to imply that the battery will be warmed up suffiently when pre-heating the cabin for 30 min.

Get Amped, I agree with your assessment that the amount of energy to heat the batteries is the same but in my experience with the Roadster and now the S, it appears the use of the battery heats it quicker than heating it with other means. I am not sure how the pre heat function works (if it indeed does) on the S.

Olan, I would be interested in the information that tells me how the pre-heat function works. All I know at this point is that there is a phone app coming to pre-heat the cabin. I am currently using 4.0 so maybe 4.1 and/or 4.2 shows this information. I have not seen a message yet that says my battery is heating on the S although I have seen that message on the Roadster but only when charging it.

@Theresa - yes I assumed that the cabin and battery heating functions were separate and could be controlled independently, but I could be totally wrong.

My post is really a plea to TM to solve this issue for every owner by giving them the option of preheating their battery with the app if they so choose.

Posts from real owners like yourself are invaluable to this forum, so thanks for taking the time. Guys and gals like yourself are the real force for positive change with S, and when I get mine in a month it will be better because of people like you.

I have also found that the air suspension does not work when the batteries are cold. It was 8 F here last night (Louisville). After a few bumps I went to the control panel and all of the air suspension options were grayed out. After several miles the setting was restored to Standard and it worked fine.

Bucket;
If you have any charging at all at work, you can do exactly the same thing: set the amp draw low enough via the touchscreen that it takes longer to get "Full" than you are going to be parked.


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