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Regen limited due to cold today
- Thread starter cinergi
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- Driving Dynamics Model S
mknox
Well-Known Member
Very rare in the Southern Ontario region where winters aren't really that cold. (It gets quite damp and uncomfortable with temperatures going above and below freezing, but generally not that "deep freeze" where block heaters are needed). Here's the funny part, though: I work as a senior executive at an electric utility where we are promoting EVs (we have a Volt), but no public or employee charging infrastructure! This is something I'll be tackling with the senior leadership team, and I hope to be able to promote some charging infrastructure at local malls and so forth.
I noticed the same thing this AM. About 40 degrees out, and no regen. I also had a line at the top (red) side of the gauge, which I assume restricted the output of the battery as well, although I did not test this. What I was surprised by was that it didn't warn me more vociferously, because I was quite surprised when the car didn't slow as quickly when I took my foot off the accelerator.
I left the car outside last night, not plugged in. Tonight it will be plugged in, and I'll check in the AM if the regen is off.
I left the car outside last night, not plugged in. Tonight it will be plugged in, and I'll check in the AM if the regen is off.
Vger
Active Member
Yet another one of those innumerable "undocumented features" that this forum is invaluable for discovering! Since Many of us will be getting our cars in the depth of winter, it is sure good to know these little quirks in advance.
BTW, even the Roadster is not truly "on/off" with regen; it just does not tell you so obviously what the current limit is, given its traditional mechanical power meter. If you watch carefully as you begin a drive after a full range mode charge, you will see the power meter needle gradually venture further and further to the left, as the regen capacity is restored.
BTW, even the Roadster is not truly "on/off" with regen; it just does not tell you so obviously what the current limit is, given its traditional mechanical power meter. If you watch carefully as you begin a drive after a full range mode charge, you will see the power meter needle gradually venture further and further to the left, as the regen capacity is restored.
KBF
Model X owner (formerly Cdn Signature Model S)
It's not about charging, it's about keeping things a bit warmer. The question here is that it seems as though an unplugged car doesn't keep itself warm enough to prevent regen limitation.
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Sorry, I was being a bit facetious, pretending Winnipeg was superior since we have plugs everywhere.
<- guess I should have used one of these! It IS quite funny that you work for a utility, though! 
The Roadster is on/off with regen when it's related to the cold. It's varied only when related to a range mode charge. So the Model S is exhibiting different behavior than the Roadster (with respect to cold & regen). Will be interesting to see what it's like when it's REALLY cold ...
harry
Member
According to the Tesla service people the yellow dotted line shows up when the battery is fully charged and can't take much additional charge. The line is very useful because it shows you how much regen you can expect before you cruise up to a stop sign expecting normal regen and have to stomp the brakes. As you use some power from the battery the yellow line will gradually move down the scale (indicating that the battery can take more regen) and then will disappear when the power level is low enough that full regen can be accepted. To the limit of my understanding the line has nothing to do with ambient temperature -- and shouldn't, since the battery pack is fully temperature controlled.
I can confirm the Roadster regen is on/off when related to cold which is the way it should be based on the chemistry. That's why it's a bit odd to phase in and out. In any case it's quite disconcerting for those of us who live where it's cold most of the year. Also a bit odd that it starts at about 40 deg F! Where I live you will end up driving home without regen for almost half the year. The Roadster is much better; it won't limit regen until you get down to about 3 or 4 C.
I wonder if it has to do with thermal management in different regions of the battery. In other words, perhaps the average brick temp was 40 F, but there were pockets at around 36F, low enough to turn off regen in those areas but not the whole pack until temps evened out more.
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The Roadster touchscreen slows a little in deep cold but remains quite functional, much better than most of the Prius screens I've seen in deep cold. I would assume the S is as good as the Roadster. No evidence that they cheaped-out on the touchscreen.
Agree to that!
Seems to me that the "I want 200 km by 08:00"-functionality is becoming more and more useful. Then the battery would more often be warm from charging when you start driving, and the car would know when to start pre-heating the battery if necessary. This is in addition to the advantage of reducing time spent at high SoC enormously. Couple charge mode selection with physical location and this would be effortless most of the time. The selected charge parameters might even be displayed in large letters on the screen for a while so that it can be checked from the outside.
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The problem is that the battery cannot always take the regen. The reason may be that the battery is fully charged, or that it is too cold (the topic of this thread), or that it is too hot.
They just need to divert the generated power somewhere else anytime the battery is unable to take the charge. (like to heat or cool the battery instead of charging it when its too cold or hot, or simply dumping the excess power to a dummy load)
That way the braking effect of the regen would be uniform.
They may be able to do this now and just need to tweak their firmware?
I don’t know if they have access to a dummy load or if the heating circuits can handle that much power. Anyone know?
They just need to divert the generated power somewhere else anytime the battery is unable to take the charge. (like to heat or cool the battery instead of charging it when its too cold or hot, or simply dumping the excess power to a dummy load)
That way the braking effect of the regen would be uniform.
They may be able to do this now and just need to tweak their firmware?
I don’t know if they have access to a dummy load or if the heating circuits can handle that much power. Anyone know?
Hmm, lets see... say, we heat 10 litres of water at 0 degrees celsius with 60kW for 5 seconds. Temperature will rise for 7 degrees.
As regen-limit goes away after a few minutes of driving, there isn't a lot of oportunity for full-power regen cycles and in principle it should be possible to simply heat the coolant when battery is to cold to charge.
The question is thus is it worthwile to add those resistors and swhitches which cost money and weight and can/will brake?
And will only be usefull when the baterry is to cold to charge. Heating the battery when full is not always prudent and when it is allready to hot you obviously wouldn't want to heat it even further.
In this light, limiting the regen power to 2/3 of max power looks much better(cheaper and more reliable and predictable) solution.
Definitely worth just about anything to get reliable uniform braking. You can't expect the average consumer to put up with instructions to watch for this little yellow line and make sure they brake harder to compensate. As soon as someone misses the warning or has no idea about it and has an accident - whammo lawsuit.
Hopefully they have a dummy load in the circuit now and just need to use it more effectively. Otherwise they need to add one or fix the non-uniform braking in some other way.
But brakes working one way and then another is going to get someone in trouble.
It really isn't a problem once you drive the Model S. in general, when first driving on a "cold" morning I am not accelerating and regening all that aggressively anyways. The limiting does not change the draining characteristics that much. A "cold" ICE vehicle also accelerates and brakes differently. This is largely a non-issue for me. The Tesla implementation seems pretty close to ideal - communicates what is happening far better than the ICE vehicles I have had in the past.
I have noticed no difference in how hard I need to brake when regen is limited. Or are you referring to the fact that you need to rely on the brake pedal instead of the regen?
The brake pedal itself seems to work the same to me.
As for difference, will the average consumer, in your mind, be annoyed by being able to set regen to standard or light/off?
Yes. With no regen you have to use the brake pedal.
Right, the brake pedal force doesn't change.
Setting isn't the issue. The issue is that if you are used to having regen and sometimes it isn't there, it can be disconcerting for a new Model S driver. This isn't really an issue once you are aware of the behaviour but there will be some folks who will complain loudly about it.
I suspect that the cold weather issue won't be a problem once you can set the end charge time (needs verification).
:-(
I've asked ownership for information on what happens when it gets even colder (e.g. 0F), about warming while plugged in, plus general comments about having regen limited or removed for 5 months of the year every day after work not being ideal. I was hoping for a better-insulated pack or some such (this area was an area of feedback I gave Tesla very early on in Model S development).
BTW, WRT braking differences -- it's very pronounced in the Roadster because it's on/off and because the brakes are weak. It's not nearly as pronounced in the Model S. And from a lawsuit perspective... well, has anyone won a lawsuit due to wet brakes? There've been times when brakes in all of my cars were completely useless due to water. Loss of regen is much safer than that.
mknox
Well-Known Member
Sorry, I was being a bit facetious, pretending Winnipeg was superior since we have plugs everywhere.
Ha Ha, yes we Ontarians don't have Winnipeg's superior infrastructure. But seriously, don't block heater outlets limit power and/or cycle on and off to balance load and/or only work below certain temperatures? I wonder if they would, or even could be used for EV charging?
And by funny I mean embarassing :redface:
