Limited regen after charging?

setheryb

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#1
Saturday morning I installed a NEMA 14-50. My model 3 has been plugged in overnight. When I've woken up the last 2 mornings and gotten in to drive, I notice that I have 3-5 dots on the left side of my regen/energy use bar. It's been roughly 45F the last few nights, but its not that cold in my garage, maybe mid-50s

Any idea why after being plugged in all night and charging to ~80% this would happen? Wouldn't being plugged in keep the battery/vehicle conditioned?

Also, I feel like this wasn't happening when I was using the standard 110 outlet to charge before installing the 14-50
 

Bibs

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#2
It's not the charging that does it, it's the final state of charge:

Lithium ion batteries don't like being at either very high or very low SoC. So when the battery gets charged near max capacity, the software limits regen in order to "burn down" to a healthier SoC faster.
 

Bibs

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#3
Thus, if you are doing a road trip and want to start the day with 100% SoC, you want to do two things:

1. charge at a rate so you reach 100% just before you leave (ie, don't let the car sit at 100% for hours)
2. Expect that you will have limited regen until you reach ~80% SoC (the higher the SoC, the more dots you'll see)
 

setheryb

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#4
Thus, if you are doing a road trip and want to start the day with 100% SoC, you want to do two things:

1. charge at a rate so you reach 100% just before you leave (ie, don't let the car sit at 100% for hours)
2. Expect that you will have limited regen until you reach ~80% SoC (the higher the SoC, the more dots you'll see)
I’m not charging to 100% only to maybe 80% or about 260 miles
 

Diamond.g

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#5
I’m not charging to 100% only to maybe 80% or about 260 miles
SoC and pack temp are what cause limited regeneration. It can also cause limited power (acceleration) as well, but that has only been reported during track runs, haven't seem power limits on low battery yet (or at least I am not aware of it).
 

setheryb

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#7
SoC and pack temp are what cause limited regeneration.
That's what I thought. I guess I figured that charging to 260 wouldn't cause that. And that being plugged in would regulate the pack temperature.

I lowered my limit a little bit, near 240, and set it to not start charging until closer to when I'd be getting in the car.
 
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#8
It's the temp, not the amount of charge in your situation. Anything below 50 degrees and extended cool down time will result in the M3 going into restricted regen mode. The M3 does not have a battery heater so you can't preheat them. It relies on waste heat to bring the battery up to temp and decides to limit regen until the pack is up to temp.

What you can do to try and prevent this is calculate your charging start time such that the battery pack charges to your requested level (80%) close to the time you want to drive the car. For example: if your commute is 50 miles a day and you leave for the office at 7am every day and you get 30 miles per hour of charge, set the charge time to 5am and your battery pack will be nice and warm when you leave and you shouldn't hit the limited regen mesage.
 

setheryb

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#9
The M3 does not have a battery heater so you can't preheat them. It relies on waste heat to bring the battery up to temp and decides to limit regen until the pack is up to temp.
I thought I remembered Elon saying they would power the motors to heat the battery pack even if the car were still or plugged in. But I might have interpreted what he said incorrectly.
 

JWardell

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#10
I thought I remembered Elon saying they would power the motors to heat the battery pack even if the car were still or plugged in. But I might have interpreted what he said incorrectly.
That's correct, the Model 3 can send power to the motors when parked to heat the battery. I don't think we have determined yet exactly when it does this though, is it activated when pre-conditioning the climate from the app?

I am confused by this thread in general, while I expect regen to be limited with charged over 95%, I do not think it is the case when at 85%. But maybe there is a curve and combination of battery percentage and low temperature or something?
Waiting for the cold months to figure all this out myself*
*hopefully I have to wait a while
 

setheryb

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#11
That's correct, the Model 3 can send power to the motors when parked to heat the battery. I don't think we have determined yet exactly when it does this though, is it activated when pre-conditioning the climate from the app?
I'm glad I'm not the only one who understood it that way. Maybe my current temperatures are just above the point where it would initiate that level of heating.

I am confused by this thread in general, while I expect regen to be limited with charged over 95%, I do not think it is the case when at 85%. But maybe there is a curve and combination of battery percentage and low temperature or something?
Waiting for the cold months to figure all this out myself*
*hopefully I have to wait a while
Yeah. I'm a little unclear myself. I've not gotten a message that says region is limited, but I've seen the dots on the regen side of the line. I'm reducing how much I'm charging up to tonight and see if that makes a difference in the morning. I'll definitely report back on that. It's not that cold here yet, but maybe it's cold enough?
 
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MelindaV

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#12
That's what I thought. I guess I figured that charging to 260 wouldn't cause that. And that being plugged in would regulate the pack temperature.

I lowered my limit a little bit, near 240, and set it to not start charging until closer to when I'd be getting in the car.
I set mine to just around 80%, starts charging at 630A (and with my commute, normally recharges back to the set limit in about an hour 10 minutes) and ready by the time I leave. And haven't yet seen the dots.
 

setheryb

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#14
So charged to 235 miles this morning and told it not to start until 4:30am, which still finished before I needed it to. And no dots this morning. Temperature is about the same though its rainy and wet today.

It could've been either the amount I was charging to or not charging until the morning that got rid of the dots.
 

MelindaV

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#15
So charged to 235 miles this morning and told it not to start until 4:30am, which still finished before I needed it to. And no dots this morning. Temperature is about the same though its rainy and wet today.

It could've been either the amount I was charging to or not charging until the morning that got rid of the dots.
ok - so this morning I noticed the dots. maybe they have been there every other morning too, but today was the first I've seen them. No difference in regen braking at all. Leaving my neighborhood, I come up to a light at the bottom of a slight hill (about a 10% slope), and can still get down to 2 or 3 MPH before needing to step on the brakes, so certainly does not appear regen is limited.
 

setheryb

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#16
ok - so this morning I noticed the dots. maybe they have been there every other morning too, but today was the first I've seen them. No difference in regen braking at all. Leaving my neighborhood, I come up to a light at the bottom of a slight hill (about a 10% slope), and can still get down to 2 or 3 MPH before needing to step on the brakes, so certainly does not appear regen is limited.
Agreed. It's not being limited except maybe at the far extreme, but I haven't had the regen get that far.

Also, while I said the dots weren't there when I got in the car this morning...they were there again when I got in my car to go to lunch. My guess is that, at least this time, it had to do with the outdoor temperature which was about 56F when I got in.
 

jsmay311

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#17
Agreed that the root cause is the temperature and not the (modest) SOC.

For some reason (I believe it's due to the particular chemistry of the cells that Tesla uses, but I don't know that for certain), Tesla's battery packs are more affected by cold temperatures regarding regen than other EVs. I'm most familiar with the Volt, and it maintains regen rates (both in kW and C-rates) far higher than the Model 3 at much colder temperatures. (I posted about this previously here.)

And as @JWardell mentioned above, we don't know everything about the battery pack heating behavior yet. But I think it's safe to assume that the Model 3 won't draw power 24/7 when it's plugged in to heat the battery pack all the way up to its *optimal* temperatures (by which I mean where you won't see any reduced regen). Given how high the optimal battery pack temperature appears to be, that would be a hugely wasteful, costly, bad for the environment, etc. I would hope it would only draw enough power to keep the pack above some minimum temperature, below which it would cause more fundamental, serious problems (like inability to accept a charge).

Timing the start of the charge to finish soon before you leave does seem like the best strategy. (It's too bad Tesla still hasn't added common-sense scheduled charging options to allow for better control of when a scheduled charge ends rather than only controlling when it begins!)
 

JWardell

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#18
Wow. I was expecting regen to not be limited till you got down into the 40's, not 50s.
There's a good chance I just never noticed considered our power/regen bar is so freaking small.
Would be nice to pull up actual battery temps. Really need to get moving on my geek display :)
 
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#19
That's correct, the Model 3 can send power to the motors when parked to heat the battery. I don't think we have determined yet exactly when it does this though, is it activated when pre-conditioning the climate from the app?

I am confused by this thread in general, while I expect regen to be limited with charged over 95%, I do not think it is the case when at 85%. But maybe there is a curve and combination of battery percentage and low temperature or something?
Waiting for the cold months to figure all this out myself*
*hopefully I have to wait a while
The few times I've charged up to 100% I had regen back within 20 miles. That's about 93% charge. The only times I've seen low regen below 90% have been in temps below 50 degrees.