Regenerative Braking Optimization

[mineguy]

I live up in mountains, so often see 1-2% battery increase after going down a mountain for like 2 minutes.
I'm looking to optimize the battery increase as much as possible so I have a few questions:

- If I'm barely touching the acclerator is it still regen braking? cause I can definitely feel the car still slowing down really fast if I'm barely touching accelerator.
- If my max % is set to 80% and I drive all down hill to work, is the car really regenerating any electricity?

 

[jjrandorin]

Let me ask a question. When you drive down the mountain to work, are you not planning on driving back up the mountain to go back home? Unless the answer is "you are correct, I am not going back home", the energy use is going to balance out.

 

[XPsionic]

I live up in mountains, so often see 1-2% battery increase after going down a mountain for like 2 minutes.
I'm looking to optimize the battery increase as much as possible so I have a few questions:

- If I'm barely touching the acclerator is it still regen braking? cause I can definitely feel the car still slowing down really fast if I'm barely touching accelerator.
- If my max % is set to 80% and I drive all down hill to work, is the car really regenerating any electricity?

There's a little horizontal bar near your speedo that shows you if you're regening or not. If you're at 80% to start the day and only gain a few percent on the way down to work, you're fine, you'll be regening.

 

[jjrandorin]

There's a little horizontal bar near your speedo that shows you if you're regening or not. If you're at 80% to start the day and only gain a few percent on the way down to work, you're fine, you'll be regening.

Unless the OP charges their car right before they leave, its entirely possible that, even though they have "only 80%" charge, the battery may not be able to take full regen because its cold. "Cold" for batteries is different than "its 70 degrees in my garage, its not cold".

 

[XPsionic]

Unless the OP charges their car right before they leave, its entirely possible that, even though they have "only 80%" charge, the battery may not be able to take full regen because its cold. "Cold" for batteries is different than "its 70 degrees in my garage, its not cold".

the little bar will show if there's regen or if the batteries are too cold for that to happen. IIRC during 2021, an update increased regen rates for colder batteries vs the 2020 and prior firmware.

 

[jjrandorin]

the little bar will show if there's regen or if the batteries are too cold for that to happen. IIRC during 2021, an update increased regen rates for colder batteries vs the 2020 and prior firmware.

yes, it will, but the OP is talking about "maximizing regen" and they likely wont be able to do that unless they plan their charging to end right before they go to work, because if they dont, their battery will likely be cold every morning, no matter where they live.

When I drive into the office, and pull my car out of my fully enclosed, drywalled garage, with insulated garage doors, with my car charged between 80-90%, I have regen dots every morning, no matter what time of year it is. I live in southern california, so, like you, dont have real "winter".

Im just saying that its kind of a waste of time to try to "optimize regen of driving down a mountain" because you have to drive back up the mountain at some point. It will all balance out.

 

[Tam]

- If I'm barely touching the acclerator is it still regen braking?

I am not sure what's the question is.

If you go downhill without touching the pedal, your car would do a regen and you can see the green indicator on a consumption graph.

If you touch the pedal to increase the speed, the green regen might still light up if there's no need to consume the power from the battery.

- If my max % is set to 80% and I drive all down hill to work, is the car really regenerating any electricity?

Yes. If your battery is full at 100% while going downhill, there's no more space to pack in any more power into your battery so there's no need for regen and your car would glide as if it's an ICE. It's the actual fullness not the setting of maximum charging setting at 100% that prevents the regen.

 

[mineguy]

Well my question is more if my battery is full at 80% and I set the maximum capicity to 80%. and I go down a massive hill regen braking, will it increase it over 80% even though I set it to maximum 80%

 

[XPsionic]

Well my question is more if my battery is full at 80% and I set the maximum capicity to 80%. and I go down a massive hill regen braking, will it increase it over 80% even though I set it to maximum 80%

yes, the max charge you set is only for when you're plugged in

 

[Gasaraki]

I live up in mountains, so often see 1-2% battery increase after going down a mountain for like 2 minutes.
I'm looking to optimize the battery increase as much as possible so I have a few questions:

- If I'm barely touching the acclerator is it still regen braking? cause I can definitely feel the car still slowing down really fast if I'm barely touching accelerator.
- If my max % is set to 80% and I drive all down hill to work, is the car really regenerating any electricity?

Yes. Anytime you see green on the energy bar. It's regening. Even when you step on the accelerator a little, it can stay in the green if it's a slight downhill.

 

[Gasaraki]

Well my question is more if my battery is full at 80% and I set the maximum capicity to 80%. and I go down a massive hill regen braking, will it increase it over 80% even though I set it to maximum 80%

Yes it will.

 

[Gauss Guzzler]

Unless the driver or cruise control applies the brake any excess energy coming from a downhill drive will add charge to the battery regardless of how much you are pushing the gauss pedal. So just drive the speed you want and know that it's always putting everything it can into the battery.

It will still do regen even at very high charge states (>95%) but it's often limited by low temperatures as others noted. So if you find that you're having to use the brakes more than you'd like and truly want to optimize you could do scheduled-departure charging so that your battery is pre-warmed.

TLDR: The only time energy is ever lost unnecessarily is when you hit the brakes while the top bar is displaying the limited regen dots.

 

[lolder]

Well my question is more if my battery is full at 80% and I set the maximum capicity to 80%. and I go down a massive hill regen braking, will it increase it over 80% even though I set it to maximum 80%

Yes, it will go over 80%. That limit only applies when you are plugged in.

 

[AlanSubie4Life]

- If I'm barely touching the acclerator is it still regen braking? cause I can definitely feel the car still slowing down really fast if I'm barely touching accelerator.

Yes. Green bar under the speedometer is where it's at if you really want some quantification of regen (note the scale is extremely nonlinear, though).

- If my max % is set to 80% and I drive all down hill to work, is the car really regenerating any electricity?

Yes. It'll go over the max as others have said. (Last I checked it appears to add range in 3-4 rated mile chunks (probably 1kWh, or maybe 1%?), though obviously it's actually doing it continuously; there is some quantization/hysteresis.)

If you are finding that your car complains about limited regen at some point on your descent, set your nightly charge level to a lower level. Otherwise don't worry about it.

It's quite common at 80% charge level in warm temperatures, with a battery that has been sitting, for the car to limit regen AFTER you regen substantially on a large hill (so regen will be rapidly reduced as you regen more). (This is presumably to prevent any lithium plating since the reincorporation of the lithium is probably rate limited. Speculation.) This will be both noticeable from a braking perspective, and it will be audible. When it starts happen, the car appears to switch to heating the battery (you start to hear a sound similar to the pre-conditioning for a Supercharger - motors become quite whiny). I don't have TeslaFi to confirm this stator warming, but it would make sense that the motors switch over to a less efficient mode (it's only a few kW so you won't notice it in braking power - but it will improve "regen" braking slightly (it would be a combo of battery heating and regen at that point)) and heat the battery in an attempt to restore more regen, rather than heating the brakes. And audibly that appears to be what happens. Speculation.

Anyway, details; if you're not having limited regen messages and you're not using the brake at all, you're doing the best you can, and you should just forget about it. The solution if you have that issue is to lower your SOC as mentioned. The optimal situation (for "slosh losses") is to minimize both acceleration and regen, with zero use of the brakes (it's a little more complicated than that for overall efficiency since speed also matters).

 

[mineguy]

Ok thanks this definitely seems to be a battery is cold issue, the regenerative braking is very limited, I can tell by the amount of dots at the top and the alert message. I seem to only loose about 1% of potential charge per trip so like $0.1 oh well.

I'll try and charge it to 70% instead of 80% and see if it prefers that, I'll probably have to do it in a couple months though temperatures are really hot now and regenerative braking seems to do better as a result.

 

[Mattopotamus]

Ok thanks this definitely seems to be a battery is cold issue, the regenerative braking is very limited, I can tell by the amount of dots at the top and the alert message. I seem to only loose about 1% of potential charge per trip so like $0.1 oh well.

I'll try and charge it to 70% instead of 80% and see if it prefers that, I'll probably have to do it in a couple months though temperatures are really hot now and regenerative braking seems to do better as a result.

The closer you can stay to 50% the better for the battery, so definitely play around with your commute and charge %.