Limited regen going downhill

[MikeBur]

I was driving in this morning with a higher charge and 43° and did not get any regen limiting. If it's something overheating than colder weather would help.

There does appear to be some sweet spot here. I keep having to steal my wife’s car to play, so it will take time to get comprehensive, comparable, results though here’s what I’ve found so far (and I’m not trusting this data yet, so apply a truck-load of salt). Also this from from polled API data, not streaming or CAN bus.
At 37F regen is limited from start. Car takes about 15 minutes of driving to warm battery enough from motor to get rid of warning. Regen at this point is dismal, I’m looking at ~5-10kW. Car gets cold again after 30 mins parked... I’m hoping this gets “tuned” because for shopping trips in cold this could be impactful, and hope there’s supplemental heating for battery if cabin conditioning is on,

 

[shs1]

Mike, Greg,

I don't drive the 3 everyday, so it may be a few days before I get another data point. It was 17 °F here this morning so that would have been a good test of the overheating theory, but not driving the 3 today. As to TACC, there are many curves on the roads down to town, no white line on the right and no traffic, so I tend not to use TAAC and certainly not Auto Pilot.

 

[shs1]

I got to drive the 3 to town today and started with 200 miles of range (65%). I took a slightly different route down to town, and the limited regeneration warning came on once just before I got to my destination. Outside temp was 48 °F.

 

[MikeBur]

I got to drive the 3 to town today and started with 200 miles of range (65%). I took a slightly different route down to town, and the limited regeneration warning came on once just before I got to my destination. Outside temp was 48 °F.

Sounds more like this is not battery full, not temp. Would appear to be limitation during extended regen
Needs more investigation... I wonder if I can steal my wife’s 3, find a mountain, and put a logger on it

 

[run-the-joules]

From Tesla:

"In this instance it looks like regenerative braking was limited due to the possibility that the vehicle had gone through too many regen "cycles". It sounds like you were driving through an environment in which regenerative braking was taking place continuously over a period of time.

The Battery management system reduces regen when a fair amount of regen occurred recently. The purpose is to preserve the cells and guarantee long term capacity retention. "

 

[gregincal]

From Tesla:

"In this instance it looks like regenerative braking was limited due to the possibility that the vehicle had gone through too many regen "cycles". It sounds like you were driving through an environment in which regenerative braking was taking place continuously over a period of time.

The Battery management system reduces regen when a fair amount of regen occurred recently. The purpose is to preserve the cells and guarantee long term capacity retention. "

Which kind of sucks. The Model S doesn't do this, and going down a mountain is one of the times when one pedal driving is really nice. That said, I now start my commute at 70% instead of 90% and the problem almost never happens, but I'll be interested to see how it works driving down a much longer slope than the one in my commute.

 

[favo]

Well, if you start at close to a full battery and add more charge due to a lot of regen at the start of your trip, at some point the regen is going to have to be disabled, since the battery can't go past 100%. Pretty sure that applies to any EV, S and X included, no?

 

[gregincal]

Well, if you start at close to a full battery and add more charge due to a lot of regen at the start of your trip, at some point the regen is going to have to be disabled, since the battery can't go past 100%. Pretty sure that applies to any EV, S and X included, no?

If you start at the top of the hill. In my case I climb the hill and then descend, so if I start with a 90% battery the battery is never more than 80% during my descent.

 

[favo]

If you start at the top of the hill. In my case I climb the hill and then descend, so if I start with a 90% battery the battery is never more than 80% during my descent.

Gotcha. Apparently, though, your starting battery level does make a difference, while all other things are held equal? Maybe the 2170 batteries are more sensitive to recharge rates at 80+% capacity. Not sure if Tesla ever does partial regen. Is it always full or nothing?