Total Pack Power vs. Ownership Lifetime

[Rhodesman]

Slightly cryptic title I'm sure, but I am looking to see what others have gathered on the current state of their Powerwalls "
total_pack_energy" from the Tesla API. Details about accessing the API can be found here: State And Settings and the total_pack_energy stat comes from the data obtained via the API link: https://owner-api.teslamotors.com/api/1/powerwalls/:battery_id/status (once one has attained an oAuth token, see api website for details if needed).

I've been collecting data from my Powerwalls since June and I've been noticing that the total stored energy of my pack has been decreasing a lot over time. I would assume this would happen with any batteries but I had my Powerwalls install in February of this year and since then I have lost about 13% of my total pack energy which seems like a lot for less than 1 year of use and also considering the cars don't seem to loose that much total power in the same time frame.

In any regards, I wanted to create a post where we can collect such data and share it with others to help gauge if our Powerwalls are loosing more or less energy storage over others. See the data below and post yours if you can:

• Install date: Feb 2019
• Today's Date: Dec 2019
• Total Powerwall(s): 2
• Expected Energy (1x = 13.5kWh): 27.0kWh
• Current Reported Energy: 23.542kWh
• Percentage Lost: 13%

 

[Dan123]

I don't understand how to access API, and how to obtain an oAuth token. I am not a software engineer.

 

[charlesj]

Does that 23.54k shows 100% on the Tesla app?

 

[Rhodesman]

Does that 23.54k shows 100% on the Tesla app?

It does yes, but it shows 100% even though it also showed 100% when the pack had over 24kWh of Total Pack Power.

 

[Rhodesman]

I don't understand how to access API, and how to obtain an oAuth token. I am not a software engineer.

Fair enough. I'm working to move my powerwall software to "the cloud". Once I do that, there will be a website where all you have to do is enter your tesla account info and it will do the rest for you. Still working on a few bugs with it and trying to figure out the best security measures because I really don't want to collect or store your tesla account information so trying to weigh the best options so I'm not collecting that data except to activate a link for you.

 

[m3-pw2]

I pulled the data from tesla api for my 2 powerwalls, and below is the summary.
Back in Dec, I wasn't aware of this API, and I did a test by drawing 20% of battery, and the 2 powerwalls generated 4.5kWh AC. Rough estimate is energy capacity that was 8% below expected.

• Install date: Mar 5 2019
• Today's Date: Aug 25 2020
• Total Powerwall(s): 2
• Expected Energy (1x = 13.5kWh): 27.0kWh
• Current Reported Energy: 23.774kWh
• Percentage Lost: 12%

 

[eml2]

Here is my data:

• Install date: Sep 19 2017
• Replacement dates: Nov 2017 & Feb 2018 (due to bad cooling fans)
• Total Powerwall(s): 2
• Today's Date: Aug 25 2020
• Expected Energy (1x = 13.5 kWh): 27.0 kWh
• Current Reported Energy: 27.522 kWh
• Percentage Lost: gain???

 

[cwied]

It'd be interesting to know what that API is actually reporting on. I also have data that on the face doesn't seem to make sense:

• Install Date: Feb 16 2018
• Today's Date: Aug 25 2020
• Total Powerwalls: 2
  
• Nameplate Energy: 27000
• Current Reported Energy: 27664
• Percentage Lost: -2.4% (2.4% gain)

I think you would have to monitor the number over time to see if it really reflects battery degradation. Given that my batteries are over two years old, I would have expected some degradation by now. I'm averaging over one full discharge per week to qualify for the SGIP rebate.

 

[gpez]

• Install Date: March 25 2019
• Today's Date: Aug 25 2020
• Total Powerwalls: 1
  
• Nameplate Energy: 13500
• Current Reported Energy: 12323
• Percentage Lost: 8.7%

 

[gpez]

FYI here are the curl commands for those interested:

First get your <bearer token> by calling the login API with your <email address> and <password> that you use for teslamotors.com.

curl -X POST -d "grant_type=password&client_id=81527cff06843c8634fdc09e8ac0abefb46ac849f38fe1e431c2ef2106796384&client_secret=c7257eb71a564034f9419ee651c7d0e5f7aa6bfbd18bafb5c5c033b093bb2fa3&email=<email address>&password=<password>" "https://owner-api.teslamotors.com/oauth/token"

This will return a JSON blob with your <bearer token>:

curl  --header "Authorization: Bearer <bearer token>" "https://owner-api.teslamotors.com/api/1/products"

This will return a JSON blob with your "Home Energy Gateway" ID(s) <gateway id> which is needed for the final calls:

curl --header "Authorization: Bearer <bearer token>" "https://owner-api.teslamotors.com/api/1/powerwalls/<gateway id>/status"

You'll need to make one for each of your Powerwalls listed in the /products call.

 

[power.saver]

• Install Date: June 10 2018
• Today's Date: Aug 25 2020
• Total Powerwalls: 2
  
• Nameplate Energy: 27000
• Current Reported Energy: 27570
• Percentage Lost: -2.1% (2.1% gain)

 

[m3-pw2]

I think you would have to monitor the number over time to see if it really reflects battery degradation.

I did a test and drain batteries from 100% down to 5% to find out how much energy I can get out, and also noticed a significant loss versus what was expected. The experiment was documented here: Energy in 2 powerwall drained from 100% down to 5%.

My batteries are located in the basement and should not degrade that fast due to extreme temperatures. I mainly use them in backup mode, so no cycling, except recently I have signed up for the grid services where they do use the batteries up to 60-90 times a year.

 

[rtabagaboy]

I don't have a system yet, but should get one soon. it would be useful when recording this info if people could also add typical storage temperature and daily % drain on battery and or peak loads? Maybe also intended use (IE: Grid backup only, peak Demand Reduction... others?) More information is always better when looking for trends that make sense.

 

[ParaAdBellum]

• Install date: Dec 2019
• Today's Date: Oct 2021
• Total Powerwall(s): 2
• Expected Energy (1x = 13.5kWh): 27.0kWh
• Current Reported Energy: 22.74kWh
• Percentage Lost: 15.8%

 

[ParaAdBellum]

• Install date: Dec 2019
• Today's Date: Nov 2021
• Total Powerwall(s): 2
• Expected Energy (2x = 13.5kWh): 27.0kWh
• Current Reported Energy: 22.647kWh
• Percentage Lost: 16.12%

 

[ParaAdBellum]

• Install date: Dec 2019
• Today's Date: May 2022
• Total Powerwall(s): 2
• Expected Energy (2x = 13.5kWh): 27.0kWh
• Current Reported Energy: 22.578kWh
• Percentage Lost: 16.37%

 

[bkp_duke]

How are you guys obtaining this info?

Are you accounting for the fact that there is 5% at the bottom that the firmware will never let you discharge?

 

[power.saver]

How are you guys obtaining this info?

Are you accounting for the fact that there is 5% at the bottom that the firmware will never let you discharge?

You can make this call to the local API:

https://<powerwall_IP_address>/api/system_status

Look for "nominal_full_pack_energy" in the response.

 

[bkp_duke]

You can make this call to the local API:

https://<powerwall_IP_address>/api/system_status

Look for "nominal_full_pack_energy" in the response.

Interesting, I get the following:

nominal_full_pack_energy - 54519
nominal_full_pack_energy - 13373
nominal_full_pack_energy - 13386
nominal_full_pack_energy - 13591
nominal_full_pack_energy - 14169

Since I have a 4 x PW2 system, I'm assuming the first number is the total aggregate kwh, and the 4 subsequent numbers are the numbers for each PW2. Kinda makes sense given that the last PW2 was installed 2 years after the first 3.

Still, if that is correct, I'm showing no degradation at all.

Am I missing something?

 

[power.saver]

Interesting, I get the following:

nominal_full_pack_energy - 54519
nominal_full_pack_energy - 13373
nominal_full_pack_energy - 13386
nominal_full_pack_energy - 13591
nominal_full_pack_energy - 14169

Since I have a 4 x PW2 system, I'm assuming the first number is the total aggregate kwh, and the 4 subsequent numbers are the numbers for each PW2. Kinda makes sense given that the last PW2 was installed 2 years after the first 3.

Still, if that is correct, I'm showing no degradation at all.

Am I missing something?

No, your data looks good. The first value is the system total, then each PW.

My smaller 2 powerwall system shows:

"nominal_full_pack_energy":27950
"nominal_full_pack_energy":13930
"nominal_full_pack_energy":14020

So similar results as yours. Installed in May 2018.