Fox App v2 - TonyM1958/FoxESS-Cloud GitHub Wiki

Information based on frequent questions about how the new Fox App works. For a quick tour of the app, go to Me, Links and select the Tutorials tab.

Fox uses different metrics in their v1 and v2 apps and web site:

• Fox App v1 and the web site show Total Yield. This is the energy output by the inverter, generated from the solar panels and battery. The yield is used as the basis for the inverter revenue shown. This is just a notional figure indicating Return On Investment (ROI).

• Fox App v2 show PV Yield and Production. These both refer to the energy input to the inverter from your solar panels.

Obviously, as these are measuring different things, the numbers are not the same.

The first statistic is Production: Production is the amount of energy generated by the solar panels attached to your inverter; Export is the amount of energy you exported to the grid. Self-consumption is simply the difference i.e. the amount of energy you produced that was retained. The retained energy is not the same as the amount you consumed as it includes things like system losses and battery charging. In the chart above, I retained 47% of the PV energy I produced (and exported 53%).

The second statistic is Consumption: Consumption is amount of energy you used; Grid Purchase is the amount of energy you purchased from the grid. Self-sufficiency is simply the difference i.e. the amount of energy you consumed that did not come from the grid. In the chart above, 99% of my consumption did not come from the grid (and so, 1% did come from the grid).

You can calculate system efficiency from the figures: the energy input is Production + Grid Purchase (698.5 + 2.3 = 700.8kWh); the energy output is Export + Consumption (373.3 + 264.1 = 637.4kWh); the difference between the input and output energy is the System Losses (63.4kWh); this is 9% of the input energy (63.4/700.8) so the system is 91% efficient. June has 30 days (720 hours) so the average loss is 88W.

This assumes that the battery has the same charge at the beginning and end of the measurement period so it's best to do this using Monthly data. The variations in charge for Daily data are too great to give worthwhile results.

Note: if you have more than 1 inverter, the Consumption is not measured correctly and you cannot work out your Consumption or System Losses from the data presented by Fox. Fox displays a Total Revenue figure in Fox app v2 that is different to the Total Income figure shown in Fox app v1 and the cloud web site.

Both of these are based on the Feed In or Unit Income value you set in your site (or plant) settings. I have this set to 15p/kWh.

The figures displayed are calculated based on the energy counters held by the inverter. These start at 0 when you system is installed and count up through the life of your inverter. Here are examples of my current counter values (as read directly from my inverter over Modbus):



In Fox app v1 and the web site, the Total Income is based on the total energy output by the inverter to date (shown as Total Yield in the app and called Output Energy Total above). In my case, this reads 10,973.3kWh and so the Total Income shown in the app and web site is £1,645.9 (10,973.3 x 0.15).

In Fox app v2, the Total Revenue is based on the total PV energy generated to date (Lifetime Production in the app and called From Solar above). In my case, this reads 9,668.9kWh and so the Total Revenue shown in the app is £1,450.3 (9668.9 x 0.15).

The new battery information screen now shows the lowest cell temperature, as opposed to the previous Battery Temperature (which is the BMS electronics temperature, up to 10C higher than the cell temperature). This now gives a much better measure of the actual cell operating temperatures. The effect of temperature on battery performance is explained here.

Within a stack of batteries, the lowest cell temperature is usually the bottom battery and temperatures rise by a few degrees as you go up the stack.

If your battery cells are cold, they may not charge or discharge as fast as expected because the current is limited. You can check what the current limits are in the Fox app v2 by tapping your inverter on the home page and then selecting Detailed Parameters, Battery Information. You will see a screen like this:



The Battery temperature shown is the current lowest cell temperature. The Max charging and Max discharging current are the limits the BMS has set. To work out the effective battery charge power, multiple the Max charge current by the Battery voltage. Note that the BMS also limits the charging current when the battery SoC is above 97%, so you may also reduced charging due to this as well.

When setting charge times in winter, it's important to allow time for the battery to heat up and also charge at reduced power. This oftens means you need to double the time you would normally allow for charging.

Fox has updated the way that Charge Times work in the App v2 so that you can enable / disable a time using the sliders shown above. Note that the sliders shown above do NOT enable / disable Charge from Grid; you need to enable / disable Charge from Grid by tapping on the time and changing the setting inside the time period.

When a time period is disabled, the time is cleared (00:00-00:00) and Charge from Grid is disabled, regardless of what is shown in the App. For a time period to be used, you must set the sliders shown above to Enable and then tap Submit.

When you try to change Min Soc On Grid (Battery Reserve), Min Soc or Work Mode, you may get the error "Unsupported Function Code". This happens when Mode Scheduler is Enabled and is because those settings are currently being controlled via the schedules and cannot be changed. To make changes, you must set Mode Scheduler to Disabled.

You may also get this error when setting Charge Times. It's the same reason, you cannot set Charge Times when Mode Scheduler is enabled as the schedules are controlling charging. In addition, when Mode Scheduler is enabled, any Charge Times that you have set will be removed from the inverter.

The times in the power and SoC charts in the App do not use the same time axes, so it may look like the times are wrong. If you tap the chart, a dotted line appears and the time is shown. Note that the dotted line that denotes the times is in different places on the top and bottom chart and do not line up correctly with the time shown.

Fox holds up to 8 time segments that can be enabled or disabled. When you save a schedule, previously used time segments are set to disabled but are not deleted.

This means, when you reload your schedule, you may see a mix of enabled and disabled time segments. The disabled time segments can be random and confusing. If you swipe left on a disabled time segment, it can be deleted to clean up what you see.

Fox has added a tab for Agile Integration into the App under Mode Scheduler. This is configured with your Octopus account information so it can lookup pricing. The integration provides 2 modes of operating:

• price: charging slots are setup when the price drops below a trigger price each day
• time: a fixed number of 30 minute charging slots are setup using the lowest prices available each day

When you enable the Agile Integration, Fox takes over control of the your inverter from the cloud. The inverter is set into schedule mode and schedules are downloaded and updated by Fox. When you do this, you are locked out of making changes. This means you can no longer make:

• changes in work mode
• changes in Min Soc and Min Soc On Grid
• setting charge times

When setting charge slots, the Agile integration may raise your Min Soc up to 100%. As a result, the battery isn't available when the charge slots end. To enable it again, you have to disable Mode Scheduler but it is automatically enabled again as long as you have the Agile integration configured...

Because of these issues, in my opinion, you should not configure Agile Integration for your inverter. If you have done this and want to disable it, you need to remove your Octopus account information from the app / web site.

There are alternatives to manually setting your charge times to match the Agile pricing. Some people use automations in Home Assistant. I use 'daily.ipynb' as described here. You can also run this as a scheduled job using Saturn Cloud as described here