no regeneration on first trip

[Brian May]

Hello,

We live on a mountain. So the first trip of the data involves driving down the mountain.

In a conventional petrol car, we would change down a gear to save the need to use brakes all the way down the mountain.

In a Tesla, you would typically expect to be able to use regenerative braking to save the need to use the brakes all the way down the mountain.

But in practice the Tesla always enters restrictive regeneration mode. As in there is almost no regeneration. So we need to use the brakes excessively, which in turn runs the risks of the brakes overheating, because there is no other option on the Tesla to reduce excess speed.

This happens even on warmer days. And with the heater on. If anything this seems to be getting worse over time.

Yes, I know Tesla now has auto preconditioning at a set time, but problem is during lock down, we don't have a set departure time anymore.

Any ideas?

Regards

 

[Solarman004]

Hello,

We live on a mountain. So the first trip of the data involves driving down the mountain.

In a conventional petrol car, we would change down a gear to save the need to use brakes all the way down the mountain.

In a Tesla, you would typically expect to be able to use regenerative braking to save the need to use the brakes all the way down the mountain.

But in practice the Tesla always enters restrictive regeneration mode. As in there is almost no regeneration. So we need to use the brakes excessively, which in turn runs the risks of the brakes overheating, because there is no other option on the Tesla to reduce excess speed.

This happens even on warmer days. And with the heater on. If anything this seems to be getting worse over time.

Yes, I know Tesla now has auto preconditioning at a set time, but problem is during lock down, we don't have a set departure time anymore.

Any ideas?

Regards

Typically, what is the state of charge of the battery as you start down the hill? If greater than about 90%, the car will limit the regen regardless of temperature.
You're correct that a cold battery will also limit regen.
When you observe this issue, what are the outside temperatures, and if you park in a garage, what are the overnight temperatures in there?

 

[Blue heaven]

Hello,

We live on a mountain. So the first trip of the data involves driving down the mountain.

In a conventional petrol car, we would change down a gear to save the need to use brakes all the way down the mountain.

In a Tesla, you would typically expect to be able to use regenerative braking to save the need to use the brakes all the way down the mountain.

But in practice the Tesla always enters restrictive regeneration mode. As in there is almost no regeneration. So we need to use the brakes excessively, which in turn runs the risks of the brakes overheating, because there is no other option on the Tesla to reduce excess speed.

This happens even on warmer days. And with the heater on. If anything this seems to be getting worse over time.

Yes, I know Tesla now has auto preconditioning at a set time, but problem is during lock down, we don't have a set departure time anymore.

Any ideas?

Regards

Is this your model S? Are you getting regen at the start of the trip? What ever the cause the important thing is the car is protecting its battery pack.

 

[Brian May]

The car is charged to 90% maximum. I tried also limiting charge to 80% also, but doesn't seem to help.

Yes, maybe this is to protect the battery. But would be good if there was some transparency as to why it was doing this. Also need to protect the brakes...

Typically restrictive regeneration doesn't kick in immediately until the car reaches the steepest part of the downhill - i.e. when we need it the most. So seems to depend on the rate of regeneration as well as the temperature.

Weather is could at the moment, but I this happens even on hot summer nights/days.

 

[Onshore]

Sounds quite normal for the scenario described. Charging to a high SOC level, cooler time of year, first trip of day on a cold battery, starting at the top of a mountain. All of these factors work against regen. It would be hard to put together a better set of circumstances to minimise regen!

Try this:

Set your charge limit to around 70%. Used Scheduled Departure based charging and set a departure time.

This will preheat the battery in anticipation of you departing at that time.

If you do all that and still seeing "almost no regen" as you put it, then there might be an issue.

 

[Brian May]

Thanks to lock-down, can't use Scheduled Departure based charging and set a departure time because our departure times vary significantly day to day. Not to mention weekends which are different anyway.

I guess I can try charging to maximum 70%, but doubtful it will help any more then I reduced to 80%.

Might just have to put up with it.

Just seems a unfortunate that we are loosing all this energy every time we use the car, because every trip involves driving down the mountain.

 

[Onshore]

Thanks to lock-down, can't use Scheduled Departure based charging and set a departure time because our departure times vary significantly day to day. Not to mention weekends which are different anyway.

I guess I can try charging to maximum 70%, but doubtful it will help any more then I reduced to 80%.

Might just have to put up with it.

Just seems a unfortunate that we are loosing all this energy every time we use the car, because every trip involves driving down the mountain.

Starting first trip of the day at the top of the mountain means that the drivetrain is unable to do any significant "work" to warm up. You don't want regen trying to dump 80kw of power into the cold battery.

Even with varied start times, you can still use Scheduled Departure as long as you have a rough idea the night before what time you are leaving the next morning. The expected departure time can be changed every time you plug in, it's not fixed.

If you don't want to use the scheduled departure, another option is to remotely turn on Climate in the car about 15 mins before you depart. This will preheat the battery a little, but not as much as the departure feature

Which model is your car?

 

[Brian May]

Oops. Forgot to say. 2016 Model S.

I think I tried preheat, and it didn't help, but I really should retry that again.

 

[Onshore]

Model S has dedicated pack warmers. I think you have to set range mode to Off

 

[Tasdoc]

Afaik older Model S has a maximum regen power limited to 60kw. If the hill is much steeper than that you will have to use breaks regardless of the state of the battery.

My MS75D at 90% cannot take more than 22kw charge. At 80% it’s likely to be around 35-40kw even if the battery is nice and warm. So the crossover point where the charge rate drops below 60kw and regen rate becomes limited by the battery is probably around 60-70% SOC

 

[paulp]

Oops. Forgot to say. 2016 Model S.

I think I tried preheat, and it didn't help, but I really should retry that again.

I’ve recently had the same experience in my model S. Normally coming down the freeway its regens big time, and I get almost to the coast on no power consumed from when I departed. No braking needed. Last time I departed with the battery at 90% and a cold wet morning, and regen was there but weak. Normally its been warm weather and my battery lower. I also have full regen set. This is the first time I’ve gone down the hill in the cold.
Hence I think cold is definately going to impact you, which as you said isnt good for the brakes.

 

[aegidius]

I have a 2016 S. I don't see restricted regen unless I charge to the full 100%, and it goes away in minutes. But then it's rarely very cold where I live, so that may be a factor.

 

[Brian May]

Model S has dedicated pack warmers. I think you have to set range mode to Off

First time I have heard of that. Maybe only newer cars? In any case I have confirmed range mode is off.

So in summary, I probably should try one/more of the following:

* Preheat car 15 minutes before drive.
* 90% battery might be too much. Might need to reduce to 70%. Maybe even 60%.

I suspect in my case I am getting limited by temperature, not battery charge. But sure would be good if the software could say as much.

 

[PC__LoadLetter]

Do you use a Google calendar (or similar) to plan your day? Put appointments in, with their addresses etc?

I used to. It was good for reminders. But nowadays I don’t have many extracurricular activities & switched to task/based reminders instead.

I believe calendar-based reminders can be linked to your car’s nav and possibly thereby its preconditioning. I think.