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what I learned today - or why my powerwall doesn't fully charge from solar every day

miimura

Well-Known Member
Aug 21, 2013
7,397
7,400
Los Altos, CA
The other option for people on EV-A is to push the start of Part-Peak from 7am to sometime later in the day when the PWs should already be filled. If you are normally full by 1pm, maybe make Part-Peak start at 2pm. However, it may then have the tendency to discharge starting at that time instead of the start of Peak at 4pm.
 

ucmndd

Well-Known Member
Mar 10, 2016
9,448
18,351
California
The other option for people on EV-A is to push the start of Part-Peak from 7am to sometime later in the day when the PWs should already be filled. If you are normally full by 1pm, maybe make Part-Peak start at 2pm. However, it may then have the tendency to discharge starting at that time instead of the start of Peak at 4pm.
Interesting thought - but a reminder for others reading along that EV-A peak starts at 2pm.
 
This sounds like a lot of work to avoid the simple solution of just setting your reserve higher. Much easier than trying to outsmart the algorithm.
I want to use as much power as necessary to defend against "peak rates" - but also want the battery to top off when it can so I always exit the peak rate period at:

100% - [peak consumption]

_IF_ you do not do this - you will _ALWAYS_ exit peak @ reserve % based on predictions…

I want to exit the peak rate period at 100% - [peak usage %] - NOT "reserve %"

the personal problem I have with current behavior is it leaves the battery @ [reserve%] for over 12 hours day - where as my typical peak usage is 25% or less - I'd prefer to live at 75% or more - but have the option of using more battery _IF NECESSARY_

this problem is do to a lack of policy control - I agree we shouldn't need to "outsmart" the algorithm - the fact that some people agree with this thread demonstrates this is a problem and the current settings options lack sufficient control.

there should be an option/toggle:
  • TOU charge battery to predicted "peak usage" kWh… <----- current behavior
  • TOU fully charge batteries during mid-peak
or something like that.
 
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Vostok

Active Member
Jul 1, 2017
2,624
3,045
Sydney
Interesting thread. I’ve encountered similar frustrations/head-scratching with TBC which is why I no longer use it. Its black-box algorithm does weird and unpredictable things and I don’t like it. Also, since the input data does not include the rate for feed-in-tariffs, nor for 100% green power grid surcharges, I don’t believe it can properly optimise. A cost optimisation algorithm can’t work on incomplete input data.

By importing all my 5-minute PW2 data and doing “what-if” calculations comparing how TBC did work to other possible algorithms and what would they have done, I came up with a simple set of rules that I think work slightly better than TBC in terms of optimising cost (at least for my generation/usage profiles), but also have completely predictable behaviour and most importantly the user will understand what the system will do.

So I’d like Tesla to add a “Simple Optimised Control” on top of the Self-Consumption and TBC options. SOC would have self-consumption as its underlying mode of operation but with 3 simple toggles that modify it:
  • Do not discharge the battery during off-peak
  • Fully charge the battery from the grid before the end of the off-peak period
  • Fully charge the battery from the grid before the end of the shoulder period (or partial peak as you call it in the USA)
Each option includes the option above it, hence they are increasingly aggressive in terms of trying to keep your battery full and minimise use of grid power during peak times.

Because so many houses in Australia have rooftop solar now (about 30%) there has been a collapse in feed-in-tariffs. I used to get 21c/kWh, it’s now down to 2.5c/kWh. It will likely soon be zero and then potentially we will have to start paying to export at certain times of the day when there’s simply too much electricity.

So increasingly you actually don’t want to export but keep as much power for yourself (self-consumption) and have additional control to minimise peak grid usage and use the battery to tariff shift. That’s what this 3-stage toggle would do.
 
Last edited:
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aesculus

Still Trying to Figure This All Out
May 31, 2015
4,967
2,892
Northern California
  • Do not discharge the battery during off-peak
  • Fully charge the battery from the grid before the end of the off-peak period
  • Fully charge the battery from the grid before the end of the shoulder period (or partial peak as you call it in the USA)
Does TBC even charge the PWs from the Grid in AU? I don't think there is any mode in US that I have seen this since almost all PW users in the US took a government tax credit where the PWs were considered solar devices, and not just stand alone batteries. This prohibits us from charging from the grid until 5 years (that time is even suspect but good enough).

So I doubt you see much interest from Tesla for any TBC scenario that includes grid charging along with solar charging. We just got the ability manually grid charge (with a big disclaimer about the tax credit issue) and Export Everything. And some of our utilities are even watching what gets sent back and if you exceed your solar threshold, they won't credit you for the extra energy.

And if you think the algorithm is confusing and hard to pin down now, wait until they can add in grid charging too. :)
 
Interesting thread. I’ve encountered similar frustrations/head-scratching with TBC which is why I no longer use it. Its black-box algorithm does weird and unpredictable things and I don’t like it. Also, since the input data does not include the rate for feed-in-tariffs, nor for 100% green power grid surcharges, I don’t believe it can properly optimise. A cost optimisation algorithm can’t work on incomplete input data.

By importing all my 5-minute PW2 data and doing “what-if” calculations comparing how TBC did work to other possible algorithms and what would they have done, I came up with a simple set of rules that I think work slightly better than TBC in terms of optimising cost (at least for my generation/usage profiles), but also have completely predictable behaviour and most importantly the user will understand what the system will do.

So I’d like Tesla to add a “Simple Optimised Control” on top of the Self-Consumption and TBC options. SOC would have self-consumption as its underlying mode of operation but with 3 simple toggles that modify it:
  • Do not discharge the battery during off-peak
  • Fully charge the battery from the grid before the end of the off-peak period
  • Fully charge the battery from the grid before the end of the shoulder period (or partial peak as you call it in the USA)
Each option includes the option above it, hence they are increasingly aggressive in terms of trying to keep your battery full and minimise use of grid power during peak times.

Because so many houses in Australia have rooftop solar now (about 30%) there has been a collapse in feed-in-tariffs. I used to get 21c/kWh, it’s now down to 2.5c/kWh. It will likely soon be zero and then potentially we will have to start paying to export at certain times of the day when there’s simply too much electricity.

So increasingly you actually don’t want to export but keep as much power for yourself (self-consumption) and have additional control to minimise peak grid usage and use the battery to tariff shift. That’s what this 3-stage toggle would do.
I use Time Based control but would like to see the following options:

During Peak run the home off the Powerwalls but have an option to prioritize home use of solar and send the excess to the grid.

During Off-Peak prioritize home use of the solar with the excess being used to recharge the Powerwalls. However, if the Powerwalls won't get fully recharged before the next Peak period, have an option to prioritize solar to recharge the Powerwalls at that point. And if the Powerwalls still won't get fully recharged before Peak, have in option to charge the Powerwalls from the grid at that point.
 

Vostok

Active Member
Jul 1, 2017
2,624
3,045
Sydney
Does TBC even charge the PWs from the Grid in AU? I don't think there is any mode in US that I have seen this since almost all PW users in the US took a government tax credit where the PWs were considered solar devices, and not just stand alone batteries. This prohibits us from charging from the grid until 5 years (that time is even suspect but good enough).

There are no rules in Australia that prevent a house battery being grid charged at any time. With TBC mode, I have seen the PW2 being grid charged, mostly at night during offpeak or during the day if there’s little solar production. But it wasn’t predictable when it would and would not decide to do this. Similarly on nice sunny days, TBC would stop charging the battery at anywhere between 50% and 70% and just start exporting. And then the battery would not be full when peak tariff started. It drove me nuts and I hated it.

Getting solar and battery installed here is very easy and no red tape. The installers handle everything. When I had my solar and PW2 installed in 2019, it took 3 weeks between confirming I wanted them to do the job and having it up and running. Things only become a bit more complicated if you want to install more than 10 kW of solar per phase (3 phase residential is common here) or more than 20 kWh of battery.
 
I just started to have similar behavior, but I'm in Self-Powered Mode, not Timed-Based Control. My Powerwalls are now only charging to 97% before exporting to the grid. They continue to trickle charge @0.2kWh until full. Not sure why the change, but would prefer achieving 100% state of charge before exporting.

IMG_1901.PNG
 

Vostok

Active Member
Jul 1, 2017
2,624
3,045
Sydney
I just started to have similar behavior, but I'm in Self-Powered Mode, not Timed-Based Control. My Powerwalls are now only charging to 97% before exporting to the grid. They continue to trickle charge @0.2kWh until full. Not sure why the change, but would prefer achieving 100% state of charge before exporting.

When any Li-Ion battery is nearly full, the charge rate will slow down a lot and the solar excess exported. But I haven’t ever seen the kind of behaviour shown in your screenshot, where it slowly creeps up to 100% charge like that, and with such a sudden change in charge rate. I get behaviour like this, and always have:

9F231268-185D-416B-93C9-245F50451807.jpeg

What SW version is your PW2 on? I am on 22.18.3.

Maybe log a call with Tesla support?
 
When any Li-Ion battery is nearly full, the charge rate will slow down a lot and the solar excess exported. But I haven’t ever seen the kind of behaviour shown in your screenshot, where it slowly creeps up to 100% charge like that, and with such a sudden change in charge rate. I get behaviour like this, and always have:

View attachment 866319

What SW version is your PW2 on? I am on 22.18.3.

Maybe log a call with Tesla support?
My historical charging pattern always matched yours - fully charging up to 100%, then export. I just changed to 22.26.1 on Wednesday so this may be related - although it did not effect Wednesday's behavior. I plan to reach out to Tesla tomorrow (or Monday).
 
Congratulations. The observed charging behavior is exactly what you want for optimal lithium battery lifetime. I'm on 22.26, and I'm not seeing that behavior yet.

All the best,

BG
@BG,

I suspected that might have been the reason. I know from my car that the slowing charging rate as it gets full is the healthiest for the battery. I think I always wondered in the back of my mind why the Powerwall didn't have the same characteristics. I hope you're right.

bwb1
 

NikoV6

Member
Nov 13, 2018
37
24
Uk
I would like the option of preventing Powerwall exporting anything to the grid in Time Based Control. I find that if I am generating say 3.5Kw, house taking 0.5Kw and the battery 2.7Kw, the excess 0.3Kw is going to grid! Happening today with battery at 44%SoC.

Battery is set to max charge at 5Kw. I would like all solar going to battery and to run house. I don't get export tariff payments so want all the solar for myself!

Its a pain to have to keep switching over to Self Powered

Any suggestions?
 

aesculus

Still Trying to Figure This All Out
May 31, 2015
4,967
2,892
Northern California
I would like the option of preventing Powerwall exporting anything to the grid in Time Based Control. I find that if I am generating say 3.5Kw, house taking 0.5Kw and the battery 2.7Kw, the excess 0.3Kw is going to grid! Happening today with battery at 44%SoC.

Battery is set to max charge at 5Kw. I would like all solar going to battery and to run house. I don't get export tariff payments so want all the solar for myself!

Its a pain to have to keep switching over to Self Powered

Any suggestions?
Can you build pricing models that force it to work that way? Try making the sell price $0.
 

Gwgan

Almost a wagon
Aug 11, 2013
3,232
2,599
Maine
I would like the option of preventing Powerwall exporting anything to the grid in Time Based Control. I find that if I am generating say 3.5Kw, house taking 0.5Kw and the battery 2.7Kw, the excess 0.3Kw is going to grid! Happening today with battery at 44%SoC.

Battery is set to max charge at 5Kw. I would like all solar going to battery and to run house. I don't get export tariff payments so want all the solar for myself!

Its a pain to have to keep switching over to Self Powered

Any suggestions?
From the support pages
“Some utilities allow Powerwall to send energy back to the grid and claim credits during peak times. When Powerwall is able to send energy to the grid, the following energy export options will be available…”
You should have the choice to export Solar (only) or Everything (solar + battery).

Is it financially beneficial to be exporting at that time?

 
I would like the option of preventing Powerwall exporting anything to the grid in Time Based Control. I find that if I am generating say 3.5Kw, house taking 0.5Kw and the battery 2.7Kw, the excess 0.3Kw is going to grid! Happening today with battery at 44%SoC.

Battery is set to max charge at 5Kw. I would like all solar going to battery and to run house. I don't get export tariff payments so want all the solar for myself!

Its a pain to have to keep switching over to Self Powered

Any suggestions?
I'd like something similar.
During the hours of 4-9pm I'd like to run my home off solar, send the excess to the grid, have my home run off the Powerwalls when there isn't enough solar, and NEVER draw power from the grid.
During the hours of 9-4pm I'd like my home to run off solar if available, run off the grid if enough solar isn't available, use excess solar to recharge the Powerwalls, and NEVER run the home off the Powerwalls (unless there is an outage). If it looks like there isn't going to be isn't going to be enough solar to recharge the Powerwalls before 4pm then prioritize recharging the Powerwalls over the home. If that still can't recharge the Powerwalls in time then charge the Powerwalls from the grid.

If anyone has figured out a way to do this it would be nice to know. I'm surprised there isn't more demand for this.
 
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