Reduced Regen

[MacGreiner]

Last night on the way home from work I noticed reduced regen and it was only 43 deg. F. (6 deg. C) This is my first winter in this car. My impression was that reduced regen only kicked in when it was near freezing 30 or below. Is this something abnormal or within specs?
And why on earth can't we precondition the battery as you can in my i3?

 

[lbzbean]

15c seems to be the magic number on my car, leave it long enough at 14.9c and regen will be limited when you get in.

I think the battery heater only kicks in at an even lower temperature though. You can charge just before leaving which heats it up...

 

[Rocky_H]

15C seems way too high. That's 59 Fahrenheit, and I never see it limited that high. For the past couple of years, it consistently starts limiting at 50 Fahrenheit and below.

 

[PeterHG]

Also my first winter, and I'm confused/disappointed. Why should/would regen be reduced in cold weather?

 

[Max*]

Mine starts limiting at about 50F. The colder it gets, the more limited it is.

For anyone new to winter, just drive around, it'll come back once the battery warms up a bit.

 

[Rocky_H]

Also my first winter, and I'm confused/disappointed. Why should/would regen be reduced in cold weather?

Confused/disappointed? This is the physics of how lithium ion batteries work because it is really damaging to them to recharge when they are cold. And it's a graduated effect, so while they are somewhat cold, you can recharge them but not very fast. I just got a Black & Decker cordless leaf flower, and right there in the manual, it tells about how when the battery is cold, it just won't recharge at all. You have to have it inside for a while to warm up enough, and then it can be recharged. My Zero electric motorcycle is the same way. If the battery is really cold, it just can't be recharged. At least be thankful that Tesla includes a heating and cooling system in the battery pack so that it can be heated, so the slow charging limit is only for a shorter time.

 

[Big Earl]

Also my first winter, and I'm confused/disappointed. Why should/would regen be reduced in cold weather?

Recharging a cold lithium battery results in lithium plating of the anode, permanently damaging the battery. This is why Tesla and many other EV manufacturers add battery heaters. If your Tesla is cold soaked to sub-zero temperatures, your battery heater may have to run for 30 minutes or more before the battery can start charging.

The regen limitation slowly ramps in because the lithium plating is a function of charging speed and temperature (the lower the temperature, the lower the safe charge rate). The ramp is also gradual so the driver isn't surprised by an abrupt change in vehicle behavior.

The best way to minimize limited regen in the morning is to schedule your charging such that it completes at approximately the same time you're ready to drive the vehicle. This is a bit of a hassle, as you have to calculate how long it will take to charge based on your current state of charge.

 

[MacGreiner]

Confused/disappointed? This is the physics of how lithium ion batteries work because it is really damaging to them to recharge when they are cold. And it's a graduated effect, so while they are somewhat cold, you can recharge them but not very fast. I just got a Black & Decker cordless leaf flower, and right there in the manual, it tells about how when the battery is cold, it just won't recharge at all. You have to have it inside for a while to warm up enough, and then it can be recharged. My Zero electric motorcycle is the same way. If the battery is really cold, it just can't be recharged. At least be thankful that Tesla includes a heating and cooling system in the battery pack so that it can be heated, so the slow charging limit is only for a shorter time.

Yet this is never a problem in my i3 even in below zero conditions because of active battery preconditioning? And we can schedule it to precondition weekly and per day. I think Tesla is just behind on this.

 

[turtlebud]

I noticed this recently for the first time when I was parked outside at work. Temp was 43F. Then I started noticing it a few mornings when I first got into the car (which is garaged). Temp was around 50F. I was surprised that I saw it in the mornings in the garage, but based on the replies in this thread it seems normal?

For those that live in colder weather, do you see this frequently?

Could this be a sign of battery degradation? (2013 85 CPO)

 

[shred86]

You will see reduced regen when the lowest battery pack temperature is <15 C (59 F). You can't see this information without reading it off the CAN bus using an OBD adapter cable and bluetooth module with an app like TM-Spy. This is from monitoring my battery temperatures (2015 Model S 85D). Not sure if it's any different for AP2/2.5.

 

[Rocky_H]

For those that live in colder weather, do you see this frequently?

Every day. All winter.

Could this be a sign of battery degradation? (2013 85 CPO)

No, it's not.

Please keep in mind what this partial limit is really showing. That regen area goes to about 60kW maximum recharging power. That's some pretty high power charging. The wonderful happy place for these batteries to do really fast charge and discharge is like shorts and T-shirt weather--around 80 to 90 degrees Fahrenheit. So the battery just isn't going to be that warm when it's 45 or 50 degrees and will be a bit reduced on its maximum charging power. That's just chemistry.

 

[turtlebud]

Thanks @shred86 and @Rocky_H, appreciate the help. That's a relief.

 

[Rocky_H]

I just saw my old comment from someone rating it and noticed my typo that I said I had a Black & Decker cordless leaf flower. Um...well...leaves and flowers are similar.