Why is this happening (limited dynamic braking)?

[Bob Denny]

This dashed out section of the energy display occasionally appears, initially with a "caution triangle" that disappears after a few seconds. The DB limiting remains for "a while". What causes this?

 

[StanMI]

Any kind of Cold weather !! It will go away as soon as everything warms up a little.

I see the AZ location, but 54 is still a little cool.

I also believe they raise the temperature for that to happen as the weather gets colder. No facts to back that up just my own observations.

 

[djillusion]

the battery is still cold. it needs to warm up and then the dashed lines will go away and regen braking will strength.

 

[Bob Denny]

The 54F reflects the temperature in the garage where the car had been for hours. The battery just must have been very close to 54 degrees. That seems strange. It didn't go off for the entire drive of 20 minutes. Maybe I should have "rebooted" the car (gack).

 

[strider]

No need to reboot. Li-Ion batteries have a VERY limited charge rate when cold. Think about the scale of energy going back into the batteries here.

That -50kW would be equivalent to charging at 208A @ 240V, which is likely more than your entire house is rated to pull from the grid (most homes have a 200A panel). So that is a ton of power being thrown at the batteries and if they are cold at all, they can't take it.

There have long been thoughts about having some kind of external heater that could be used to shunt the extra energy but that would be complicated and heavy to tote around all the time when you only need it at the beginning of a cold drive. Another request has been for Tesla to blend in the friction brakes to give the same deceleration rate as normal regen. Tesla could do this but haven't for whatever reason.

Your options are to just pay attention to what the car is telling you and be prepared to use the friction brakes more than usual, or try to end your charging closer to your departure time so the batteries will be nice and warm.

 

[Les236]

Sounds normal, and nothing to worry about. We travel a lot, but even when we are at home and parked in the garage, we either pre-heat or not even worry about it. Once batteries are warm it will go off. It is something you need to pay attention to if you are expecting full regen since it does coast a lot. We've been on trips and had to leave when the outside temp was below freezing and of course we'd drive for at least 20-30 minutes before we had full regen. On the highway so it really didn't matter.

 

[laceyboy]

In addition to cold, regen braking is also limited when battery get full charged at 100%

 

[RedXowner]

If you would like or need the regen to work as soon as you depart your house on a trip, the night before, schedule a charge so that the car is ready at your specified departure time. When you get into the car, the battery will already be warm from charging, and you shouldn't see the dashed line. You'll have full regen braking.

 

[Bob Denny]

Thanks for the info everyone! I understand why you can't regen brake into a nearly full battery. Strangely, this does not happen when I take the car out of an unheated garage at 40 ish F but later, after parking at the coffee house for an hour or two, with the temp reading 54 ish F it happens. I;m not going to worry about it but it is strange to me.

 

[dannycamps]

This is completely normal (as of a 2019 software update). Basically regen will be limited any time the battery is under 55 degree (battery temp != outside air temp) regardless of the state of charge. Once the battery warms, the regen will be restored.

You can precondition the car to help this process along if it really bothers you.

 

[SSedan]

A windy outdoor parking lot can chill the pack more than a still garage.

 

[46&2]

Driving chills it further, depending on outside temperature and driving speed. And this is easily true at 120 km/h (aroung 75 miles per hour), or compareable speeds in .DE (I don't drive 200 there).

All with temperatures around freezing point. (0°C, no idea how much that is in an American unit like Fahrenheit, candle-light-1/12s, -1/16s, baby-diaper-filling-warmths or similar absurdities )

 

[mxnym]

Driving chills it further, depending on outside temperature and driving speed.

In fact, I've had mine drop from full regen DURING a drive. This is rare, and I've only seen it happen when it is well below freezing and I'm typically driving 55mph. I've never seen any one else report his, so it may not happen at higher speeds (power draw may add heat faster than the air removes it).

 

[Krazaak]

Optimal temperatures for the battery are a lot higher than people realize, i.e. upwards of 100F to support the highest charge and discharge rates. Peak regen is around 72kW, the same as an urban supercharger, so much more sensitive to battery conditions than even the highest home charging.

 

[StanMI]

In fact, I've had mine drop from full regen DURING a drive. This is rare, and I've only seen it happen when it is well below freezing and I'm typically driving 55mph. I've never seen any one else report his, so it may not happen at higher speeds (power draw may add heat faster than the air removes it).

I just had that. This is only my second Winter but I do not remember that happening last year.