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How to interpret the Regen Dots

mswlogo

Well-Known Member
Aug 27, 2018
6,121
4,733
MA, NH
There are a lot of folks that are new to Tesla’s with the big Q4 wave of Model 3 owners.

It was clear early in the Q4 that many people were learning (as was I) and didn’t even know what “Regen Dots” were or what dots they did see on the screen even meant at first. I think most everyone by now knows that the dots mean less regen due to a cold battery. But it recently dawned on me what that whole “power output bar” is saying. This may be totally obvious to a lot of folks but I guess I’m a little slow. So I’m sharing this “light bulb” moment I recently had with other folks maybe as slow as I am. :eek:

Say you have the UI half full of “regen dots” (that would be half of the left half of the "power bar" full of dots). That does NOT mean you will get 50% less regen or even close to it. Depending on how and where you drive, you may, and very likely, still get 100% regen. For reference the screen shot below is about 90% Regen limited.

The “Regen Dots” are the max current the battery can accept from Regen. It is not the "amount" of regen loss across all regen braking.

The display is actually showing you exactly where Regen will cut off at with the dots. So, in the 50% regen dots example, if the Green Regen Bar moving to the left, as you slow down, never reaches the dots, you’ve captured 100% regen (assuming you didn't have to hit the brakes). And often you can control it. You can often gradually slow down or aggressively slow down with regen braking. Don’t slow down aggressively (when you can) and you will capture all the energy back even if regen is fairly limited and you can't feel it so much. Even with significant Regen limitation.

Have you ever seen the green bar fully extend all the way to left? I have not come close to that. Or at least I’ve never seen it. In fact, it rarely goes past that 50% point, and if does, it’s not very often or very long. So even when I have 50% “regen dots” your getting nearly 100% Regen (if you drive smoothly).

The “limited power” dots on the righthand hand side is, exactly the same principle. The black bar (for power) will stop increasing when it hits those “limited power” dots on the right. I don’t think I’ve seen the black power bar ever peg all the way to the right. But I’m not usually watching the screen during a P3D launch

So, if your normal conservative (efficient) driving never lets the green bar hit the “regen limit dots” on the left or the black bar hit “power limit dots” on the right you’ve lost nothing in efficiency or power. And if you care about driving efficiently you probably have learned to keep a light foot down. Well, just learn to keep a light foot up too if regen is limited.

Note you can also use the Regen Dots to judge good times or bad times to charge. For me, with a 32 amp circuit, if the Regen Dots stop at around the "D". My charging will go straight to max miles/hour. If regen dots are higher it will spend energy heating the battery. So if I know regen dots will be lower because of a warm garage later, or a trip later in the day, I may decide to wait to charge when it's at or below the D. Depending on your charger capacity your point of no waste heating might be lower or higher.

Note that even with this severely limited regen below, you can still capture a fair bit of regen. You won't ever feel hard regen deceleration but if you ease off the throttle real gentle you can still recapture most of the energy. Think of it as the 120V Charging case. It just all happens much slower. I guess this is sort of like hypermiling with limited regen.

46204501364_fb7ab7fc7b_b_d.jpg
 

Moose408

Member
Nov 8, 2018
149
115
San Jose, CA
What version of software are you using? I'm 48.12.1 and I don't have dots. It is a solid white bar with a thicker bar that goes to the left or right of center depending on whether I'm using power or supplying power.
 

mswlogo

Well-Known Member
Aug 27, 2018
6,121
4,733
MA, NH
What version of software are you using? I'm 48.12.1 and I don't have dots. It is a solid white bar with a thicker bar that goes to the left or right of center depending on whether I'm using power or supplying power.

I suspect you being in CA you might never see them. I've seen them since October.
I'm on 50.6
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,412
12,656
San Diego
What version of software are you using? I'm 48.12.1 and I don't have dots. It is a solid white bar with a thicker bar that goes to the left or right of center depending on whether I'm using power or supplying power.

The dots are a function of state of charge and pack temperature. If you charge your battery to around 85%, you will start to see them with current California temperatures - once the battery is left to cool (outside) to ambient temp. At 90%, I see them regardless of temperature, but the colder it is the more dots...
 

mswlogo

Well-Known Member
Aug 27, 2018
6,121
4,733
MA, NH
The dots are a function of state of charge and pack temperature. If you charge your battery to around 85%, you will start to see them with current California temperatures - once the battery is left to cool (outside) to ambient temp. At 90%, I see them regardless of temperature, but the colder it is the more dots...

What are considered cooler temps out there?

I find if it stays above around 50F I rarely see them.
 

mswlogo

Well-Known Member
Aug 27, 2018
6,121
4,733
MA, NH
I realized something today, another lightbulb moment for dummies :)

You don't need a light "up foot" to get all regen power recouped when regen is limited as I said in the OP.

You need to think of it as reduced deceleration.

As long as the car is decelerated from what ever amount of regen you have, you are getting it ALL back.
It just takes longer the more regen is limited.

I was thinking as soon as it cuts in and decreases the effect of deceleration, that it's lost, it's not !! Because the car has not slowed down yet, what regen didn't do, it is still left as kinetic energy. The Regen is deferred, not lost.

The only time you are really losing regen (I'm purely talking about the energy) is in situations that you have to hit the brakes sooner than you would if you had more regen deceleration.

Couple other ways of saying it. If you use the same amount of brakes (the caliper kind) for two trips, one with full regen and another trip with 20% regen the recouped energy is the same !!

If say you are on flat ground. Drive 0-100 MPH. Completely lift off the throttle pedal. Let Regen Stop the car (or as close as it gets to a regen stop). If you have Full regen or 50% Regen the energy used and recovered will be the same (mostly).

It will just take a longer distance to stop with reduced regen. You will regen less over time, but for a much longer time.
Now because you traveled further, you paid a bit more in friction cost so you won't get that natural deceleration, due to friction, energy back. But you also went further.

So the trick is, you have to work a little harder to not use the brakes with reduce regen. But that is all you have to do. It's no different than learning how to "One Pedal Drive" in the first place, because Full Regen doesn't slam on the brakes either. You learn to leave room so that Regen can stop the car in time instead of using the brakes. Reduced Regen is exactly the same thing, it just needs more and more room to stop. So you just have to keep adjusting for how much room you need (within practical reason of course).

If you have 0 regen, you are SOL. Or say in heavy stop and go traffic, or lots of cars moving close you have less leeway. But in many situations you have a lot of latitude of how soon you start to decelerate.
 
Last edited:

mswlogo

Well-Known Member
Aug 27, 2018
6,121
4,733
MA, NH
It warmed up in Cleveland today to 61degreesF and yet I am still getting a limited regen message. Why?

battery still cold from deep freeze ;)

What was temps overnight night?

Very warm here today too but it was below freezing last night and my attached garage is still lagging and around 35F this morning.

I had 90% limited regen and 10% limited power this morning. Nothing surprising.

Keep in mind your car (battery) is sitting over frozen earth as well.
 

Feathermerchan

Active Member
Sep 21, 2018
1,193
934
Euless, Tx
Overall, coasting (no regen or power) is most efficient. Why? Regen does not recover all momentum. Due to inefficiencies (in charging using regen and then in reusing that energy for driving the car) I speculate that you only see about 60%. So coasting, you get to use nearly 100% of the momentum to move the car. Regen is not a bad thing it's just not as good as coasting.
I am not advocating obstructing traffic while coasting. Always be a good neighbor.
 

wtwieder

Member
Jul 26, 2018
212
112
Beachwood, Ohio
What was your state of charge?
My car was about 85 percent charged. I wouldn't think I would get a limited regen message, especially with the temp outside at 61 F. During the hot summer at the same state of charge, I wouldn't see this message. Now, I do have snow tires which according to some people somehow magically limit regen.
 

Magnets!

Member
Jan 9, 2019
661
285
California
My car was about 85 percent charged. I wouldn't think I would get a limited regen message, especially with the temp outside at 61 F. During the hot summer at the same state of charge, I wouldn't see this message. Now, I do have snow tires which according to some people somehow magically limit regen.

In my experience anything over 80 gets some regen dots even at mild temps in the 60F's. But as the OP postulates, having a few dots on your indicator doesn't mean you are losing regen necessarily. Not sure what the obsession with regen is on this forum. The hypermilers will tell you higher regen is not always the answer to more efficiency.
 

mswlogo

Well-Known Member
Aug 27, 2018
6,121
4,733
MA, NH
Coasting is definitely better than regen but when someone gets used to something, their inertia takes over when it is removed.

What do we want?
REGEN!
When do we want it?
NOW!

I used to think why doesn't Tesla emulate a load when it can't do full regen.
Now I understand why and that it would be really dumb.
Because they just tilt the curve instead (regen is not lost) so you can recover all the energy, it just takes longer.

If they emulated it with a dummy load, then it would be lost.

So you can't always have it "now". Well, actually you are often getting it now, it's just less aggressive and you don't always feel it.
Perhaps they should give an option for folks that can't deal with the change in deceleration rate (limited regen).
By adding a "Constant deceleration rate" option by emulating a dummy load when it can't be sent to the battery so they can drive.

If it's the variability you have trouble with then set regen on low. Basically the is "limited regen" a (tilting the curve).
So it's much less likely to get limited.

I think it's kind of fun and keeps the drive interesting learning to "One Pedal Drive" with any amount of regen.

It is constantly telling what the deceleration rate will be and should be no surprise when it doesn't slow down as fast.
The more dots, start slowing down sooner (assuming you can).

I was driving home tonight and was approaching a traffic light and I was unlikely gonna make it, moving to fast with 50% regen and had to hit the brakes pretty firmly. My wife comments, "you blew that one". I had plenty of time to slow down sooner. She used to squeak out 38 mpg out of a stick that I could only ever get 32 mpg out of.
 
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Feathermerchan

Active Member
Sep 21, 2018
1,193
934
Euless, Tx
I think that women have a better touch.
With the purchase of a supercapacitor company, Tesla may be able to incorporate capacitors to capture regen energy. Capacitors are less sensitive to temperature. I don't know about supercapacitors though.
 

mswlogo

Well-Known Member
Aug 27, 2018
6,121
4,733
MA, NH
I think that women have a better touch.
With the purchase of a supercapacitor company, Tesla may be able to incorporate capacitors to capture regen energy. Capacitors are less sensitive to temperature. I don't know about supercapacitors though.

I think woman have more patience.
A capacitor for just regen would be a nice first step.
 

Feathermerchan

Active Member
Sep 21, 2018
1,193
934
Euless, Tx
It could also be used to shorten charging time because it can take a charge much faster. But it would have to have a lot of capacity.
So the amount of energy stored in a capacitor is 1/2CV² so as energy stored rises, the voltage increases exponentially. Not like a battery. To use the energy to charge a battery, you need a circuit to take the wide range in voltage and regulate it. You can't just connect it in parallel with the battery. Well you can but it won't be of much use.
 

favo

P3D+ owner
Apr 5, 2012
1,059
1,166
Durham, NC
So it looks like there is room for 59 dots total--29 on each side and one in the middle. Not sure how many could actually show up. Any idea what units they represent and if the scale is linear?
 

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