Forums

PW percent charge: TEG vs. phone app.

PW percent charge: TEG vs. phone app.

New and just activated installation (very exciting).

How come the TEG web server (firmware: 1.43.3) shows a different percentage of PW charge than the phone app?

Patrick | 1 gennaio 2020

I have the same firmware and mine match perfectly - at least so far. Suggest reporting to Tesla or your installer.

bp | 2 gennaio 2020

Same issue with our new installation. Gateway web interface showing 21% - Tesla Android app showing 17%.k

Since the backup reserve is set to 20%, not clear which reading is correct.

If anyone else has seen this and was able to get the discrepancy fixed, how was that done?

smaches | 2 gennaio 2020

As you mentioned this is a new install,, it may be that you need to contact Tier I and have them 'calibrate' the sensors in the gateway. This was a common issue discussed in the old forum on the Solar City site.
Good Luck.

Atom12 | 2 gennaio 2020

The system has only been operating with the PW’s at less than 50% charge. I’m going to wait until they are fully charged before getting deeper into it.

I should have mentioned that it is the Android phone app. Both the PW SOC and the PW Backup Reserve (“Reserve for Power Outages) read about 4% low on the Android app vs the TEG.

Also, I confirmed the web interface is just reading the JSON values from:

/api/operation
“backup_reserve_percent”

/api/system_status/soe
“percentage”

It appears to me that the Android app is taking these two values and massaging them down for some reason. Perhaps as a pessimistic buffer for those folks who just use the app.

bp | 3 gennaio 2020

It appears the app reading is correct - and the web interface is reading 4% too high.

This morning, I did an off grid test to verify our new system successfully transitioned off and then back onto the grid, so the PowerWalls were at 17% (according to the app) while the web page was showing 21%.

Our system is configured (from the app) for 20% reserve power.

When the grid power was restored, 100% of the solar power went to recharging the PowerWalls, until the app showed the PowerWalls were at 20%. At that point, we stopped using grid power - and power to the house was provided by a combination of the solar panels and PowerWalls, with the PowerWalls getting any excess solar power.

Even if the web page is only using the JSON values, they appear to be 4% too high.

I've asked our installer to check on this (before I reach out to Tesla directly).

Atom12 | 3 gennaio 2020

Thanks @bp. I'd like to know the answer too.

smaches | 3 gennaio 2020

I have also noticed this difference in the app production numbers and the old solarguard.solarcity.com site that is still working at this time. I an not versed in the functionality of the software, but may chaulk up the minor reading discrepancy to the TEG as there may be proximity issues with the sensors that can bleed (flux field make and break) over to the other sensors. My system has been active for over a year and this is pretty much normal.

Also, there's conversion and transport losses to consider here that can vary with temperature and wire gauge and run length. Closed system, yes. But not impervious to the physics of our world.

bp | 4 gennaio 2020

4% isn't a minor discrepancy - since the app appears to be displaying the correct value - either the app and the TEG web page are using different data, or the app and web page are interpreting the data differently.

Also since the actual power usage is in KW (for home, solar, PW and grid), would be helpful to display the available KWh of charge, in addition to the percentage.

Passion2Fly | 10 gennaio 2020

@bp
I also have a 3-4% discrepancy between the App and the TEG readings. The TEG reads higher...
I do know that the App is right after doing several charge calculations from empty to full and getting 13.5 kWh capacity.

Regarding the kWh display additional to %, I think it’s a bad idea... I still remember the Rated Range versus Percentage hysteria with the Tesla Model 3....
People will flood the Tesla call centers complaining that their batteries lost capacity...

bp | 10 gennaio 2020

In the vehicles, the projected mileage vs. % battery charge remaining is highly variable based on many variables (speed, changes in elevation, precipitation, wind, traffic, road, curves/straights, ...). However, Tesla does provide the rated range - which tends to decline over time.

During a power outage, KWh remaining for the PowerWalls is much more useful than the % of charge, allowing customers to quickly estimate how long the charge will last based on current consumption. Just like the EV batteries, the PowerWall batteries will degrade over time, so customers shouldn't be surprised to see the KWh capacity to decline over time; solar panels will also decline in generated power over time.

Also, Tesla's warranty guarantees at least 70% charge after 10 years. Without providing the current KWh reading, owners have no easy way to determine if their PowerWalls have declined enough to trigger the warranty.

Since Tesla's warranty provides a capacity guarantee - they should be obligated to provide a reading of the current total charge capacity of the PowerWalls (and do that by PowerWall - since degradation could be in a specific PowerWall).

Passion2Fly | 10 gennaio 2020

@bp
You do have a valid point about the warranty. I just hope that Tesla is honest enough to recognize a bad battery. What would be useful during power outages is a "time left" indication. At the current kW draw and the remaining battery capacity, how much time I have left... Converting percentage to kWh can be easily done with mental math... 10% = 1.35 kWh, 20% = 2.7 kWh, 40% = 5.4 kWh etc...

bp | 11 gennaio 2020

% is useful to determine how close you are to "full" or "empty"

If the battery packs have lost charge capacity - % loses accuracy.

Agree that a "time left" based on current house power draw would be extremely useful when operating off grid.

Also strongly believe Tesla should provide the KWh - so customers know how much power is left in their batteries, and also to verify they don't have a warranty issue.

Patrick | 11 gennaio 2020

Now that our new microgrid has been online for a few days I went back and compared the SoC readings on the TEG portal vs the mobile app.

This morning the TEG portal is showing 50% vs. 47% in the app.

bp | 13 gennaio 2020

I have 3% variance right now (39% in app, 42% from TEG).

Atom12 | 13 gennaio 2020

My Observations:
TEG Android
100% 100%
95% 95%
91% 90%
81% 80%
72% 70%
62% 60%
53% 50%
43% 40%
34% 30%
29% 25%
24% 20%
19% 15%
15% 10%
10% 5%
6% 1%
5% 0%
Algebraically, Android = (TEG-5%)*100/95
While Android allows setting the backup reserve to 0%, the TEG only *allows* entering “0%” but saves it as 5%.

I'm pretty sure I know why.

bp | 14 gennaio 2020

The functionality of the TEG browser interface, at least on our TEG, is extremely limited.

The current energy status (grid, solar, home, PW) is displayed, along with the PW charge level %.

The only other options are to "change or reset password", "network", and "summary".

There are no options for setting the mode (backup-only, self-powered, advanced, storm watch), so there isn't any place to enter the reserve %.

We're running 1.43.3.

Does anyone else have more features in customer mode?

Installer mode only has the ability to run the setup again - and doesn't appear to have access to the mode/reserve % settings available in the Tesla app.

Patrick | 14 gennaio 2020

Bp - I’m showing the same limited info in the TEG portal running the same firmware release.

Passion2Fly | 15 gennaio 2020

The TEG interface only allows you to check the status of the PW and display the current configuration. Only the App allows changes.

Passion2Fly | 15 gennaio 2020

The TEG interface is the only way to configure the WiFi.

jeff | 17 gennaio 2020

Passion2Fly is right. The TEG interface is for emergencies and installers, and configuring how the PW connects to Tesla's home base: WiFi, cell or ethernet. If it isn't connecting, the phone app won't report any data. We use cell because (a) it doesn't chew up our satellite internet data plan and (b) it works during bad weather, which the satellite doesn't do so well. If we had unlimited data, I'd reconfigure it to the house WiFi. The cell connection can be erratic, especially since they depend on AT&T for this, and that carrier has been a problem since hurricane María. There are many more options in the App than the TEG connection. And another little fact I found out experientialy is shutting down the PW and gateway and rebooting it solves many little issues.