Home Battery and IoTaWatt

[quella]

So, I have had the IoTaWatt for about 8 months and I could not ask for a better supported product for my energy monitoring needs. Due to some of the storage and logging requirements, I send all my data from the IoTaWatt to a local EmonCMS server for dashboards and viewing; I also leverage the PVOutput tool.

I had a home battery installed about a month ago, but there was an issue with the transfer switch that needed to be replaced by the vendor. Nearly a month later they got around to fixing it and I have been three days without pulling any power form the grid. Yeah. The Powerwall 2 is about 14kWh of storage and can pull 7wh peak at a time. So I do not leverage my heavy loads while on battery (AC/Range) The house uses solar to power the home as well as top off the battery when I have sun. Once the house and battery have been satisfied, any remaining energy goes to the grid as an export. This is a limited home back battery system, so it required the new load panels be added which you can see in the image below.

The thin long panel on the left is my old main panel (load center). The install for a limited back required a new main breaker be added (middle center) along with a transfer switch (right top). The battery and solar inputs are brought into the lower left where you can see the Tesla connection.

With the new panels and the moving around of my mains, I had to mount a new box (lower center) which is for low-voltage cables and my IoTaWatt device. Here, because of the great CTs @overeasy provides, I can reach every location and have room to spare. Love the longer CT cables.

Today (~3:30pm) I have had a good day of sun and the battery which was at 25% when I woke up, we fully charged by 11:30am. I have few things I need to work out regarding the power for PV Output as you can see in the graph below. My “Power Used” seems to include my battery export (charging) and you can see the drop off around 10:30am where it begins to trickle charge the battery. But as you can see, the “Power Used” follows the “Power Generated” which I need to look at as it appears to include the battery export.

What I like to see below is the great day of Sun and how it is sent distributed. I would not be able to do this without the IoTaWatt unit. All numbers below are DAILY numbers which reset at midnight my time. So one can see that the home today has generated 42.27 kWhs so far. Home kWh and Consumption show the homes usage for the day. Grid cost shows the fee I pay to the grid, negative numbers are good. I added the Battery Import (discharge) and Battery Export (Charge) values so I can track how much the battery is used and charged from my solar. The battery will not charge from the grid as some system may be configred. So, only the sun will maintain the battery volume. Export kWh is specific to Grid exporting.

One more fun chart from the IoTaWatt as well.

Below is an image of my EmonCMS server dashboard with battery in the lower right showing a good 100% charge ready for the night I have also added a “Battery” dial in the top center to show negative (charge/export) or positive (discharge/import). All the data here updates every 10seconds which I love.

[overeasy]

I think one of the most impressive things here is the way the Powerwall control seems to be able to use every available extra watt to charge.

As we speak there are some open discussions going on at the OEM forum concerning “diverters” and the openEVSE variable charge based on Emoncms MQTT outputs. None of them look anything like this. Powerwall seems to have done it right. No big surprise after watching spaceX landing like Flash Gordon.

I guess you will need to decide if the powerwall is just another load (reversible), or part of the supply-side and integrate the numbers appropriately. It is a new breed.

Thanks for the update.

[quella]

Yes sir, I was also impressed that all my excess energy goes first to satisfy the battery and as the goes into trickle mode at around 96%, it is interesting to see the inverter begin to step down and begin exporting to the grid. I was impressed as well and will be monitoring it more as today was the first full one after making some tweaks.

Today I use the same configuration as the Grid with negative bring Export/Charge and positive being Import/discharge like a grid main. I think I need to find out to remove it from the “Power” setting with PVOutput which I have made changes for EmonCMS. I may have to do a custom input or change it in my setting to ignore negative power as this is not really “usage/consumption” but exporting.

So, that section you circled (which is cool) should not register that as power consumption but exporting to the battery when it is charging. That is the last part I think I need to work out to get things back as they were before the battery was installed.

Agreed, new waters here, but I’m loving it. I have to also laugh that I live in a small town like yourself and our electrical inspector never saw one or knew what a Powerwall was. Fun to chat with him and the Tesla rep about the tech and use case. Oh yea, he also liked the not only the Tesla panel installs, but my energy install as well. One for me.

[quella]

I think I found my issue with PVOutput which just required me to add the Battery1 and Battery2 inputs to the formula.

I will see how it goes Thursday when I start to charge back up (if there is Sun).

It shows just how versatile the IoTaWatt product is.

I may have my PVOutput consumption incorrect as this messed with the Energy Generated as shown below. Maybe It will correct come next day. As this is how I’m doing “Consumption” on the IoTaWatt output. Strange as it might be a formula on the PVOutput side in calculating this value.

[Wirrunna]

My Tesla Powerwall 2 was installed on Thursday.
I had found this thread by searching and liked quella’s dashboard and added a Tesla dial to my home dashboard.
When I purchased my Iotawatt I included 14 CT clamps and have now used the lot. I monitor each circuit breaker’s output from my switchboard.
Like quella my PVOutput shows the battery soaking up any excess - Wirrunna Final Upgrade 6.990kW

Just now, checking the Emoncms forum I discovered this -
Wirrunna Final Upgrade 6.990kW - My Solar PV Battery app, so I thought a “heads up” would be good as I’m sure there are more than a few Iotawatt users with batteries.

Overeasy, can we have a go at this in your forum or would you rather I asked my newby questions in the Emoncms forum ?

[Wirrunna]

@Wirrunna

My Solar PV Battery app

Oops, should be My Solar PV Battery app - Emoncms - OpenEnergyMonitor Community for the app.

[quella]

@Wirrunna congrats on the new installed battery. I love mine and my wife says it has made me even more difficult to live with. We try to optimize the battery usage as we have a single battery installed, if funds allowed I would have gone with two or three. If we did that, in most cases the grid would only be used for emergencies when we had not had enough solar.

I was not aware of the Battery App in Emoncms. I pull the data into Emoncms using the Tesla APIs documented in Github. Here I pull charge and also send that data to PVOutput as Extended feed info. The dark green is when I export from my solar to the battery (charge) and the light green is the house importing from the battery (discharge). The only portion I added to Emoncms was the battery charge level gauge via API call from NodeRed

Off to have a look at the App tool and how that plugs in and does the API calls, etc.

[Wirrunna]

The thread documents it pretty well, the only thing I couldn’t get was the battery state of charge (SOC) that you

@quella

pull the data into Emoncms using the Tesla APIs documented in Github

Would you be so kind as to give me a link to the Tesla APIs and after looking at the app maybe suggest a way of getting the SOC for the powerwall.

We have only had our Powerwall 3 days and already I’ve been told that if I ask my wife to please turn off the oven or the clothes dryer or any other electric appliance to save the charge in the Tesla then I’m out and I can take the bloody battery with me !

[quella]

Here is the API set I have used to pull the SOC on and use this for the EmonCMS battery widget.

Link: GitHub - vloschiavo/powerwall2: Tesla Powerwall 2 - Local Gateway API documentation

There are many things here and a few like SOC do not require Authentication or HTTPS. It is a rather easy query and I poll the unit every 20 seconds for SOC.

I use this API call specifically for the percentage of charge:

State of Charge / State of Energy GET /api/system_status/soe

Let me know if you have any questions.

[Wirrunna]

quella, thank you for the link.
The developer of the My Solar PV Battery app has added a simple means of getting the SOC which I have got going.

[quella]

Awesome to hear. I will have to have a look at the app and see what other info I can pull from it. Thanks for the pointer.

[forrestgrant]

@quella, It looks like you needed:

• 2 CTs for incoming/outgoing Grid
• 2 CTs for incoming/outgoing (charging) PowerWall
• 2 CTs for incoming Solar

I assume it’s difficult or ill advised to combine these with a headphone splitter to preserve inputs on the iotawatt?

[quella]

@forrestgrant I did this setup of having 2 CTs for each of my MAINS, BATTERY, and SOLAR in an attempt to collect as accurate information on these critical power systems as possible. Solar and Battery are 240v so you could use a single CT and double the value within the settings for these. I would leave it up to @overeasy on his thoughts (as an expert and developer of the tool) on the best way to handle this with the least number of CTs. Note, you will find that often one wants to measure EVERYTHING in the panel, where in reality, you will find the number of ports on the IoTAWatt to be a good number for the key circuits and then everything else if placed in the Misc. bucket. Welcome to the forums.

[forrestgrant]

@quella Thanks! I’ve been using the iotawatt and exporting to influx/grafana for several months now and LOVE it. I just had our solar installed so looking for advice. I think what you describe is the best solution. I’ll start there.

[forrestgrant]

@quella I just realized, you have two CTs on panels coming in, and two CTs on the “main” from the power wall to the backup gateway. So you can see solar generation (even if it’s being stored in powerwall) in addition to how much solar you’re using.

My powerwall is on the other side of the house (garage) so I fear I’ll need to:
A) Install a second iotawatt over there.
B) Run a very long (maybe 60 feet?) CT cable.

@overeasy do you know if 60 feet of CT would lose resolution?

[overeasy]

@forrestgrant

@overeasy do you know if 60 feet of CT would lose resolution?

That’s pushing it. It’s mostly about the resistance of the extension. Some have reported going that distance using CATx cable. I have tested long headphone extensions and found that most have too much resistance.

[forrestgrant]

That’s what I figured. A second iotawatt should work in this case, right? Since everything is aggregated in influx/grafana.

@quella do you mind sharing how you connected the CTs in your power wall? For instance, is the current bi-directional (charging vs discharging) or do you simply have CTs on the incoming from PVs and other CTs on outgoing to home.

[overeasy]

@forrestgrant

That’s what I figured. A second iotawatt should work in this case, right? Since everything is aggregated in influx/grafana.

Sure. You can aggregate data from any number of IoTaWatt to a database like influx or Emoncms.