Note: if your EV charger is wired such that the load is not visible to your home battery, and you are using the "Consumption Excludes Charging" setting, it's not possible to use the battery priority charge limit and the information on this page is not applicable. In such cases, as the load from the EV charger is not visible to the home battery, it does not know that the EV is charging and cannot react to the reduction in true excess solar.
Charge HQ integrates with home batteries to provide flexible control over how excess solar energy is shared between your EV charging and home battery charging.
When used with a compatible EV & home battery, you can set the charge priority to control how you want excess solar to be used.
In home battery priority mode, you can also nominate the home battery priority charge limit.
Once set, EV charging will commence once the home battery reaches the configured charge priority limit.
We recommend setting Battery Priority Charge Limit to between 60% and 90%, with Solar Tracking Mode set to "Solar only" (more below).
The aim is to have a bit of empty space in the home battery while the EV is charging so it can absorb the excess solar that the EV does not use, whilst still reaching the desired state of charge by the end of the day. This approach maximises the amount of solar which is used to charge the EV or battery, and minimises exports to the grid.
You can experiment with different values to see what works best for your situation.
In practice once the EV starts charging, there will almost always be some excess solar available which the home battery can absorb if still has spare capacity to charge.
This occurs because:
The charge priority limit takes advantage of the rapid response of the home battery, allowing it to act as a buffer to frequent changes in the available excess solar. This minimises both exports and imports of energy to and from the grid whilst solar charging.
This example, shows home energy consumption in blue (including EV charging) and home battery charging in green. The EV starts to charge earlier in the day with home battery continuing at a low rate in parallel. In the afternoon the EV is used and so the home battery returns to max charge rate until full.
In situations where the preference is to fill the home battery each day to cover overnight energy use in the home, setting a charge priority below 100% lets you use more of your own solar, whilst still filling the home battery.
Each home has a different energy use and charging pattern, so experiment with different charge priority limits at different times of year to optimise your solar self-consumption.
Battery priority mode works as described above when Solar Tracking Mode is set to "Solar only" mode.
If Solar Tracking Mode is set to "Solar + Grid", EV charging will occur at the minimum EV charge rate whilst there is any solar production, even if the battery is below the set Battery Priority Charge Limit. This may also result in the home battery being used to charge the EV.
When excess solar production is above the minimum EV charge rate, the remaining amount will be directed to the home battery until it reaches the Battery Priority Charge Limit. Once the limit is reached, all excess solar will be used for EV charging.
