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Anyone ever see FULL regeneration?

Anyone ever see FULL regeneration?

This isn't a necessarily a problem, just something I've been curious on. I have a LR RWD, and have noticed that regardless of conditions, even going fast downhill, when I fully let off the accelerator most that the regen green bar will go is maybe 1/2 to 3/4" shy of hitting the end and will never go fully to the left end (acceleration will hit fully to the end on the right side).

Before asking, NO these are not times where the battery is limited due to state of charge or low ambient temps. Yes I have regen setting turned up to normal.

I've heard some others are able to get the full green bar, just curious if its a limitation of RWD cars or something else, so if you have LR RWD and have seen full regen please let me know. Thanks!

amanwithplan | 30 oktober 2018

I've never seen it "top out" on the far let hand side, but I've felt I have always gotten good regen when my batteries weren't too cold and single pedal drive most of the time.

One interesting thing in the manual on Page 50 is that your "charge level setting" can also limit regen. Meaning if you're at 75% battery and limit your total charge to 80%, you may experience less regenerative braking even though the screen shows you are capable of using the full bar (no dots).

This is just a guess.

I have personally seen my green regen bar travel very far left, though never topping out. I would test and get back to you but it is too cold where I am to have full regen at the moment.

Chnowak | 30 oktober 2018

@amanwithplan - Great info on the charge level setting actually limiting, i wasn't aware of that. I still don't believe I've seen it top out even when i'm well below that, but definitely good info to know.

Just like you said, i still feel like its got great regen and i love the one pedal drive (always take some getting used to if i jump in my wife's SUV after driving my car for a while) but just since I've read elsewhere that others have seen the bar top out, was curious if it could be based on the model of car since i have RWD.

12Brent | 30 oktober 2018

Yeah, about 1-2 cm of room remaining on green regen bar at full regen for me too. I was hoping that it would top out after they increased the regeneration power with the last update, but it doesn't seem to go any further. I was wondering if dual motors could move the bar to the end, with both motors working to regen.

djharrington | 30 oktober 2018

My P has never gone all the way to the left. Musk mentioned track mode offering about 50% more regen than currently available, so maybe then.

I’d tend to not think about it much since it’s relative and I’m a numbers guy. I do have an app that quantifies regen in kW, but haven’t looked at it on the P while driving. I should have compared the P to my RWD 3 before I sold it.

Alex_SD | 30 oktober 2018

The new software release 42.x is supposed to significantly improve regen on the M3...

Chnowak | 30 oktober 2018

Even if it is different between RWD/AWD cars it seems strange that they wouldn't just max out the line regardless of how much actual kW in regen you're getting. Figured it would go all the way to the end just to represent you're getting the max amount of regen you can given your configuration - but either way good to know I'm not alone.

We'll see if the new update changes anything.

modtrois | 30 oktober 2018

I live at the top of a hill. If I set the limit to say 80% and start my drive with a conditioned battery (no regeneration limit indication). Will the car allow maximum regen going down the hill even if it results in more than 80% SOC set in the charge limit?

landoncube | 30 oktober 2018

I have 2018. 42. I don’t see any new changes in the regen screen settings, and I don’t sense any difference in regen performance at all. For example, I expected that the new more aggressive regen would allow me to come to a complete stop, but it does not.

Bighorn | 30 oktober 2018

@modtrois. Yes

Whether the meter maxes out is irrelevant. It’s an arbitrary, unitless scale. What matters is whether regen is reaching its programmed max. Perhaps they’re leaving room for boosted regen of track mode.

Bighorn | 30 oktober 2018

@landon
No stopping without energy expenditure or brake augmentation. Never expected it.

gmr6415 | 30 oktober 2018

Just got 42.2 today. The release notes state key fob compatibility and improved regen. There is definitely a noticeable improvement in regen.

amanwithplan | 30 oktober 2018

@modtrois

I am having difficulty understanding your question. You state 3 premises, you are at 80%, you have NO limit on charging, and you also have a 80% SOC limit in regen? You P1 and P3 seem to conflict.

Let me try to reword. If you limit your charge to 80% at the top of the hill when plugged in, then drive away and turn this charging limit off, you should have full regen when going down hill and charge up to beyond the 80% you started with (I myself get negative Wh readings when leaving my house from living on a hill).

However, same scenario, you charge to 80%, and you keep your charging limit to 80% when you leave the house, regen will be limited/off until it's lower so to not exceed your manual set 80% SOC cap (see manual Page 50).

@Chnowak

I have no idea how RWD vs AWD function in terms of regen. I would imagine that the AWD is capable of higher regen as you have two motors "braking" you rather than one, but the manual does not explicitly state this in my reading.

I personally have an AWD Performance, and only get lower regen when its cold out so far. A few launches later and the batteries are sufficiently warm enough to regen enough to where I like them to be.

Standroid | 30 oktober 2018

@Bighorn: Clarification please! You said "Yes", but your explanation seems to imply "No".

Like @modtrois, I live at the top of the hill: 3,000' of elevation loss in 15 miles on nearly every trip. I charge overnight to 80%, inside a heated garage and invariably get the "regen braking limited" notice part way down the canyon - even on mild days.

When mild weather returns, will I get full, unlimited regen if I slide the charge limiter up to 100% before starting my drive down the canyon?

amanwithplan | 30 oktober 2018

@Standroid

I can't imagine why you wouldn't, per the manual, as long as your battery isn't cold.

I do not experience regen limitations from my hill if battery is warm and my charger setting is not limiting.

gballant4570 | 30 oktober 2018

Its counter intuitive to me that the charge limit setting would have any effect at all on regen availability. Those are two unrelated things.

Bighorn | 30 oktober 2018

@Standroid
The Yes and the explanation were two different topics. To my knowledge, the charge limit has never applied to regen, but I haven’t looked at the manual reference cited above to see if it may now apply.

modtrois | 30 oktober 2018

@all - Thanks for the clarifications. I agree with @ gballant4570 - seems counter intuitive, I guess I will have to change my charge limit when leaving home. My hill is tiny in comparison to a 3K foot descent! @ Standroid When you slide to 100% on your next trip, I would be interested in seeing how much energy you gain on the start of your trips.

amanwithplan | 31 oktober 2018

"The amount of energy fed back to the Battery
using regenerative braking can depend on the
current state of the Battery and the charge
level setting that you are using. For example,
regenerative braking may be limited if the
Battery is already fully charged or if the
ambient temperature is too cold."

From Page 50 of manual. They don't explain it well but they do write out "charge level setting".

derotam | 31 oktober 2018

@amanwithplan, I'm not saying your interpretation is wrong....I just argue that the manual doesn't necessarily state that regen WILL be limited based on your charge limit. it says "can depend on..." which is different semantically.

This should be an easy test though shouldn't it? No matter what your SOC is, take your charge limit way below your current SOC and see if the car limits regen....or am I missing something?

amanwithplan | 31 oktober 2018

@derotam

That test should work.

Standroid | 31 oktober 2018

I'm headed down that 3,000' hill in about an hour. Unfortunately, 8" of fresh white stuff fell in the last 24 hours so I may have to back off regen if the roads aren't black. If they are black I will post a report this evening.

Bighorn | 31 oktober 2018

@standroid
Good time to point out that sometimes low regen setting is necessary in slick conditions.

Carl Thompson | 31 oktober 2018

@OP

It may simply be that the scale on the left side of the bar (regen) is the same as the scale on the right side of the bar (power to the motor) and the car is capable of sending more power _to_ the motor than it is capable of recouping _from_ regen.

I also live at the top of the hill and charge to 90%. Every morning when I get to the bottom of the hill my Wh / mile number is _negative_ which I assume means that I am regenerating past my initial charged state. (Or maybe there's so much vampire drain the car starts below 90% and I don't make it back there!)

Standroid | 31 oktober 2018

OK, here's my report from today's trip down the 3,000' hill.

First, to @Bighorn's point: the roads were not dry, but just wet with snow melt and I felt comfortable testing regen on short straightaways. I'll revisit that in a moment.

I left the warm garage with 80% charge - outside air temp was 1C (~34F) - regen set to normal. As soon as I was on the highway (speed limit 55) and headed down the hill I set the charge limit to max and had good regen braking - hooray! I quickly dropped the charge limit to ~50% and guess what? Regen was minimal-to-none. Back to max charge limit and regen was again strong.

Then, at about three minutes into the drive, the "Regenerative braking limited" message popped up and regen was minimized for the rest of the descent down the canyon - irrespective of the charge limit setting. Shortly after reaching the flat-lands the air temp rose above 4C and regen came right back.

As @Bighorn reminds us, the manual clearly cautions against use of normal regen on icy roads - ABS does not extend to regen braking. Could it be that Tesla - perhaps in a recent update - has automated that warning by using the outside air temp sensor to reduce regen at a predetermined critical temperature? My late, lamented VW Cheaterwagen would sound a chime and flash a "Watch for ice on road" warning at 4C and it could be that Tesla has taken that a step further.

Of course, it could just be that those three minutes of downhill driving in 1C air were enough to chill the battery below its own regen-limiting trigger temperature, but that seems like very fast thermal response for something so massive.

Note: mine is a non-P, AWD, 18"-aero, August-build with 42.2.

djharrington | 31 oktober 2018

I don’t think your battery is going to cool substantially in that time period. I’m more inclined to believe that what you saw was limiting based on air temp (possibly for the reason of potential ice on road as you mention). If so, pretty good move by Tesla. It would be nice to try fooling it to see if that is indeed the case. If we know the location of the outside air temp sensor, it could be fairly easy to trick it.

Bighorn | 31 oktober 2018

@Standroid
Interesting result with the toggling of max SOC. Suggestive that SOC goal may be limiting.

There’s a second issue that complicates the subject that I didn’t want to type out on my phone here, but I think it might explain your result. At a certain temp or SOC, the battery has a static regen limit from the start. If you’ve ever supercharged, you know that power input tapers with increading SOC I.e a battery at 80% can only accept about 40 kW. With regen, an 80% charge does not limit regen, which is above 40 kW; however, if the battery steadily sees regen energy in excess of that, it likely triggers a second mechanism to limit regen, as you saw. Make sense?

Standroid | 31 oktober 2018

@Bighorn

That certainly sounds plausible, but I'm having trouble devising a test case since my drive down the canyon always starts with heavy regen and 80% charge.

How about this: tomorrow I'm scheduled to head down the canyon in mid-afternoon - temp is forecast to be ~3C. Suppose tonight I only charge to 50%. Then, in the morning I set regen to the lower setting (I forget what it's called - I never use it) for half the canyon. If I haven't seen the warning at ten minutes into the descent I'll switch to Standard regen.

If the air temp is low and I'm using only the service brakes to control speed in descent (the shame of it all!) and I still see the warning does that point more strongly to outside air temp as the trigger?

If the warning does not appear after restoring regen to Normal, with charge level <50% does that support your hypothesis that it is charge level triggering?

bj | 1 november 2018

On the LEAF, the energy meter marks what the maximum regen possible is, based on current battery temp and charge state. Charge to 100% and it shows 0% regen possible. Battery cold, maybe only 60% or 80% regen possible.

Sounds like the Tesla needs something similar.

Bighorn | 1 november 2018

The cold could be a confounder, but not likely unless you’re just teetering on the threshold which I think is in the high 50s. The mass of the battery is such a temperature sink that ambient temp is not likely to change the battery temp much.

I think I’m starting to get confused with vernacular. I never thought that setting a SOC limit for when plugged in would effect a regen limit as well. If you drop SOC goal to 50 and it regens normally above that SOC, it would support that notion

If you start at 60% charge with low regen, I don’t expect any limitations cruising down the hill. Not with regular regen either. If you drop the charging screen goal to 50% and see a limit, that would also contradict my intuitive thoughts.

Standroid | 1 november 2018

To simplify my test a bit I left it unplugged overnight and to clarify, I will start today's test at 53% SOC and the SOC Goal set to Max. More news at ten (this evening, that is).

derotam | 1 november 2018

@Standroid, no, we want minute by minute updates...better yet, livestreem the entire trip!

Standroid | 1 november 2018

One modern amenity I forego by living at the top of the hill is LTE - my first bar of LTE signal comes at 16 miles as I emerge onto the plains, so no live streaming. You'll just have to be patient!

On a clear day the views make up for not LTE: http://huntting.com/wx/webcam3.html

Standroid | 1 november 2018

It's ten o'clock somewhere and here's the news:

I left the warm garage with SoC=53%, Goal SoC=Max, Regen=Low, OAT (Outside Air Temp)=7C and began the descent down the 3,000' hill on dry roads.

At 7C I wasn't expecting the the "Regen Limited" warning to be triggered by any icy road concern and there were none.

Ten minutes into the descent I was getting tired of using the brake pedal and set Regen=Standard. Almost immediately I got the "Regen Limited" warning.

I went back to Regen=Low and the warnings stopped. I set Regen=Standard again and the warnings resumed.

By the time I reached the plains the OAT was up to 12C, the warnings stopped and regen was strong.

I'm confused.

Clearly my theory that the car wants to reduce regen based on an OAT that might risk ice on the road is bogus.

I'm sorry to say that @Bighorn's theory of insufficient charging headroom is also shaky with the warnings occurring at SoC=53% and Goal SoC=Max.

I can confirm that these warnings only began as the weather began to turn cooler. We had a very mild September and early October and I never saw the "Regen Limited" warning until the first chilly morning.

What is going on? What is raising this "Regen Limited" warning?

Bighorn | 1 november 2018

How “warm” is your garage? What temp shows on the dash when you get in? If it’s in the 50s (15C or less) you’d expect a regen limit based solely on battery temperature. The car will not reduced regen for icy roads or outdoor air temp, but you should manually do that for ice.

derotam | 2 november 2018

So it said regen limited but did it also add the dots under the PRND?

Standroid | 2 november 2018

@Bighorn - Bingo - the garage temp was 11C when we left. I didn't realize the battery is such a wuss!

@derotam - Dots? No "dots" in my manual. What am I looking for and what do they tell me?

derotam | 2 november 2018

@Standroid, on the left side of the energy bar when the car is cold, the solid grey line will be dashed or dotted on the left side indicating limited regen capability. I am curious as to whether when you get the regen limited warning if it turns part of that grey line dashed on the left side. If it does not dash that line then there might be another reason for the regen limited, which I have a theory but that is moot if it dashes the line which would be expected behavior.

derotam | 2 november 2018

...relevant page in the manual is page 43 under Driving Status, below the picture, paragraph #2

Standroid | 2 november 2018

@derotam - Thanks! I never noticed that. Actually, that line is so thin and hard to see that it is not part of my normal instrument scan, but I'll have the copilot keep an eye on it next time out. Unfortunately, that may be a few days, but I will dig up this thread and post a report when I have more info.

np57 | 2 november 2018

My other car (a Bolt) has regen that brings the car to a complete stop. This is extremely useful if you do any city stop-and-go driving. I rarely have to touch the brakes to stop (exception: if someone in front of me does something unexpected.)

It is a REALLY nice way to drive and probably reduces wear & tear on the brakes even more.

Hoping Tesla brings this into the "3", via OTA update, as a third selection under "Regen" .

Bighorn | 2 november 2018

Regen to stop would require either brakes or energy to the motor. There is not enough regen energy to stop the car. The brakes need exercise too. My pads are basically new at 200k miles but I have two seized calipers. One should make a habit of having their foot on the brake when stopped even with Hold.

Carl Thompson | 2 november 2018

Since we already know the car _can_ apply the brakes by itself it seems like this is something that could be done by an OTA.

spuzzz123 | 2 november 2018

Regen noticeably more aggressive now with 42.3I see it going well above 50% “green line” taking my foot off the gas on level surfaces on the freeway. I bet going down a steep hill you’d get 80% on that meter.

cascadiadesign | 2 november 2018

I received 42.3 on my Model 3 RWD today and experience a noticeable stronger regen as suggested by the release notes..

I don't watch the display bars. I tested in my neighborhood by going to 30 mph on a level street and letting off the accelerator completely. The car went to 0 mph (a complete stop) without applying brake. Before it would only go down to about 4 mph.

Allowing regen to take the car to a complete stop in normal traffic probably won't occur often unless you back off the accelerator well in advance. It takes a while to decel the last few mph.