Charge HQ doesn't currently have official support for off-grid sites but it is a feature we hope to add in future. For now, there is a workaround with noted limitations that may enable some functionality for off-grid EV charging.
As the app developers, we don't have access to any off-grid charging sites so these settings are untested. Please reach out with feedback if you try it.
Background
In most grid-connected solar systems, when rooftop solar production exceeds the energy being consumed in the home, the additional power is exported to the grid.
In off-grid systems, when production exceeds the load from the home or battery, the solar inverter ramps down production. This means there are times when the solar system could produce more energy than it is which could be used for EV charging.
The API integrations we rely on do not currently tell us how much additional energy may be available.
Workaround configuration
Once your EV or charger and solar inverter are connected to Charge HQ, in the app go to:
- Settings -> Solar Tracking -> Advanced
- Set Solar Tracking Margin: -0.3 kW
This will cause Charge HQ to use 0.3 kW more than the available solar generation, which in turn should cause your inverter to ramp up to the maximum production available from the panels.
Your EV charge rate will be set to the sum of Excess solar production (kW) + 0.3 kW, where Excess solar production = production above that being used by the home loads + home batteries.
Other Advanced Solar Tracking settings:
- Solar tracking reference: Ensure this is set to "Excess" solar.
- Min Solar Generation: Set to 0 or empty
- Min Excess Solar Generation: Set to 0 or empty
- Negative consumption: Set to off
- Consumption excludes charging: Set to off
Please consider the following settings as they will cause different behaviours in Off-Grid setups:
Max Charge Amps & Default Charge Amps
In the Settings -> Advanced settings menu
Charge Priority
- EV priority: if Charge HQ can see that the home battery is charging, it will consider this solar output available for use and redirect it to the EV charging.
- Battery priority: the home battery will either use all available solar production, or if solar production exceeds the maximum battery charge rate the solar production may be curtailed. Whilst solar production is being curtailed Charge HQ will not be aware of available production capacity and may need assistance to start charging per below.
Solar Tracking Mode
- Solar only mode: charging will occur only from solar production that exceeds home load (and battery load if set in battery priority).
- Solar + Grid mode: EV charging will occur from excess solar production. If excess production falls below 5A, EV charging will continue at 5A whilst there is any solar production, with the difference being supplied by the home batteries.
Starting assistance
- In most cases, solar production will ramp up and down to meet the home load. If solar is being curtailed Charge HQ won't be aware of the curtailment and the available production.
- If your EV or wall charger does not have a scheduled charging period configured, each time you connect your EV it should start charging for 1-2 minutes until Charge HQ detects it and starts controlling. If you connect your EV when there is solar generation available, this initial charging will be enough to Charge HQ to detect the excess and continue using it (rather than stopping charging).
- If your EV is already plugged in, as solar generation starts each day no excess is ever visible and so Charge HQ will not start charging. You will need to manually trigger it by selecting "Charge Now" on the Charge HQ app for 1-2 minutes and then switch back to Auto mode. During this short period, the solar inverter will ramp up production to match the load from the EV charging.
- When configured in Solar only mode, if charging stops due to insufficient excess generation (e.g. increasing home load or temporary cloud cover), Charge HQ will NOT restart charging automatically and the manual charge procedure must be repeated.
Caveats
- Whilst charging, your EV will be constantly drawing around 0.3 kW from your home batteries
- If Solar tracking is set to Solar + Grid mode, your EV will charge at a minimum rate of 5A / 1.15 kW at any time that your solar system is producing energy. Some or all of this may be drawn from your home batteries.
- Charge HQ is very dependent on consistent and reliable communications with your equipment - including your solar inverter, wall charger and EV where direct control is used. If communication is lost your EV may continue to charge regardless of available solar production which may impact your home batteries.
