Regenerative braking - breaking in?

[Joelhc]

I've had my X for about 3 months now and noticed that regenerative braking doesn't seem to slow down the car nearly as much as it used to. According to the consumption gauge on the dash it appears to be regenerating similarly but without effecting the speed as much. I'm just wondering if other people have experienced this or if the car is simply "broken in" and this is how it should be? It could also just be that I've just grown used to it.

 

[ajdelange]

If the gauge says you are absorbing 10 kW you are, barring a broken sensor, absorbing 10 kW from the motors which means you are removing 10,000 joules of kinetic energy from the vehicle per second and converting most of that to electrical energy. As kinetic energy is proportional to the square of the speed and the mass the only thing that would cause less deceleration would be more mass i.e. more people and/or baggage. Thus deceleration will be more apparent at a given reading on the gauge when you are alone with no baggage than if you are taking 4 other portly people with trade samples to an anvil dealers' convention.

I'd really look into the implications of the word "seem".

 

[Joelhc]

Thanks for the informative reply @ajdelange

if you are taking 4 other portly people with trade samples to an anvil dealers' convention.

Haha, no significant change in weight besides a few holiday pounds. All the variables have stayed the same except the age of the car, the only thing I notice is that I use the brake a lot more when slowing down and as far as I can tell I'm not driving faster than usual. That's why I thought I would see if anyone else has had a similar experience. I'll see if I can try a car at the dealer to compare then take it into a service center if it really is more than my perception.

 

[bitmap]

I see you are west coast as well, so I suspect we don't have to deal with this as much as others across the country. I've found the last few weeks that even temperatures in the 50's cause my X to limit regeneration, and it doesn't always show the orange broken line on the power meter either. This must be a bug. Different regeneration levels can really change how you drive the car and it can be startling when regen isn't working and the car doesn't warn you.

 

[animorph]

I didn't notice any break-in period, but I do have the dashed yellow line on the energy meter indicating reduced regen when the temp is 50's or lower. That's normal, though I don't remember it at such high temperatures before. My X feels like it has less regen than the 3, so it's a little strange switching between the two.

 

[ajdelange]

It occurred to me this afternoon that driving into a headwind decelleration would be more perceptible than would be the case with a tail wind. I can't comment on a break in period as I haven't had the car long enough. I suppose one could argue that when the car is brand new bearings are stiffer so that it decelerates faster than when they are worn in a bit and offer less resistance. IOW it is not reduced decelleratiob from a difference in regen but from dimininshing frictional force. Seems like a pretty weak argument to me though.

 

[Yosry]

I got my x 3 month ago, i got the same feeling about the regenerative break not slow fast enough, it get worse in cold weather live in Florida, but also it seem to be fluctuate, some slow the car fast some times not

 

[jboy210]

I also suspect it due to colder weather. Like others I started noticing it when the nights went below 50F back in November. The Yellow lines were not appearing, but until I drove 20 miles are so, the regen seemed less. But after that 20 miles regen was back up to full strength.

 

[O’Ds P100X]

I’ve had my X for 2 months and I’ve been noticing the same thing, having to use the brakes a lot more. I was thinking something changed with the recent software update.

It has been cooler these last few weeks, 20s to 30s, but I’m not sure why temperature would affect regent braking?

 

[HandleX]

I noticed it too and it's because of the cold weather.

 

[bitmap]

Agreed that it is because of the cold, but not consistently displaying the dotted line on the power meter when regen is limited is a bug and is contributing to the confusion about what is going on. When it occurs, everyone should report it via the bug report voice command and perhaps it will get fixed.

 

[ajdelange]

The rate at which a lithium ion battery can be safely charged decreases as the battery becomes colder. That is why
1)The battery heater is switched on when recharging a cold battery
2)Regenerative braking is limited when the battery is cold (the motor turns into a generator when you take your foot off the accelerator and the generated energy charges the battery).

Now I haven't seen any reports of "not consistently displaying the dotted line". Can you tell us more about what you mean by that?

 

[bitmap]

Now I haven't seen any reports of "not consistently displaying the dotted line". Can you tell us more about what you mean by that?

Sure. Sometimes my X is obviously limiting regeneration (regardless of the reason be it temperature, full charge or whatever; its easy to tell when its happening), yet the power meter on the driver's display doesn't always indicate this (via the dotted line). Sometimes it does, sometimes it doesn't.

 

[ajdelange]

Normally the dashed line is shown and the power meter deflection (in the negative direction) will not go beyond the top of the dashed line. When you see the irregular behaviour is it that the meter deflection is limited but the dashed line simply isn't there?

 

[bitmap]

Yes. Meter deflection is limited while coasting/regenerating and the dashed line is not there. I am certain in these occurrences that regen is actually limited too as the car isn't slowing down like it normally would.

 

[ajdelange]

Keep in mind that that right hand pedal is an accelerator/decelerator pedal. You have control over the amount of regen through the amount you back off on the pedal. Obviously the firmware in the car can process your pedal inputs in an infinite number of ways so I am only mentioning this to suggest that you might want to see how things go if you take your foot completely off the pedal each time you check regen braking.

Another thought is that Tesla is continuously collecting data from us as we drive and feeding this into their various AI algorithms with a view to increase performance, safety etc. Perhaps they have changed the regen braking algorithm in a recent software push.

 

[ajdelange]

As a sort of summary: the decelleration is approximately equal to P/(m*v) in which P is the power (indicated on the meter), m is the mass of the vehicle and v is the speed. You have some control over P via the pedal but Tesla does too. The obvious example is that they limit P when the battery is cold but they can also be limiting it at other times for other reasons. For example if P/(m*v) becomes too large the occupants will experience uncomfortable negative g's. It's pretty obvious that speed is taken into account. In the first place you will notice this as you slow and in the second, it is clear that decelleration would become very great as you approach a stop were P not limited.

 

[EVDRVN]

If the car is new to you don't over think this, it's the temp of the pack and/or the SOC. Not the ambient temp, sensor or "a break in". It is very easy to notice regen limited by temperature restriction and/or high SOC. If you want to test this try and SC fro a very low SOC like 20% on a 120kW SC on a non-shared unit and up to 90%. After you should see a difference. If the charge speed are not over 100kW then you also have temp issues. LA has been very cold lately.