Mini Grid is often recommended over HBX as it is able to offset while charging the batteries from the PV where HBX doesn't.
What is HBX
In High Battery Transfer (HBX) mode, the system is connected to an AC source such as the utility grid; however, it will use battery power as the first priority. The AC source is locked out until needed. In this mode, the system runs on DC power for as long as the batteries can be sustained. It is expected that the batteries will be charged from renewable sources such as PV power. When the batteries become depleted, the system reconnects to the AC source to operate the loads. The batteries may be recharged during this time using the renewable source. When the batteries are recharged to a high enough voltage, the system transfers back to the batteries as the primary source (hence the name High Battery Transfer). HBX Mode commands the inverter to: o Connect to an AC source if the battery voltage has fallen below the Grid Connect voltage for the amount of time set in the (connect) Delay set point o Connect to an AC source if the battery state of charge (SOC) has fallen below the Grid Connect SOC for any amount of time o Disconnect the AC source and switch to powering the loads from the battery bank if the battery voltage has risen above the Grid Disconnect voltage for the amount of time set in the (disconnect) Delay set point o Disconnect the AC source and switch to powering loads from the battery bank if the battery state of charge (SOC) has risen above the Grid Disconnect SOC for any amount of time
Notes on Selecting HBX mode:
* HBX mode has similar priorities to the Mini Grid mode used by FXR-class and Radian-class inverters. However, it is not compatible with Mini Grid and cannot be used at the same time. To prevent conflicts when using HBX mode, make certain not to select Mini Grid. (Selection of AC input modes can be found in the inverter manual. Information on Mini Grid and other modes can be found in the inverter Operator’s Manual.)
* HBX is also incompatible with the Grid Use Time and Load Grid Transfer functions in the MATE3s. These functions do not have similar priorities to Mini Grid or HBX, but they do control the inverter’s connection and disconnection with the grid. HBX should not be used with these functions. (See inverter operators manual.)
o See the system display literature for more information on HBX mode, Grid Use Time, and Load Grid Transfer
* When deciding whether to use Mini Grid mode or HBX, the user should consider the aspects of each.
o Mini Grid logic is based in the FXR/Radian inverter and can function in the absence of the MATE3s. HBX logic is based in the MATE3s and cannot function unless the MATE3s is installed and operating.
o Mini Grid can use utility grid power to fully recharge the batteries every time it reconnects to the grid. HBX can only do so under specific circumstances.
o HBX set points have a wide range of settings. Mini Grid uses settings intended to protect the batteries from excessive discharge; however, most of its settings are automatic and do not allow customization.
o HBX works more efficiently with a larger renewable source, but there is no specification for renewable size. Mini Grid cannot work properly unless the source is larger than the size of the loads. If this condition is not met, Mini Grid will not disconnect the inverter from the utility grid.
o Mini Grid is one of seven inverter-level functions (modes) which share a single input. Selecting it prevents any other input mode from being used. HBX is a system-level function which can be combined with the settings of other input modes (other than Mini Grid).
* Mini Grid has similar priorities to the high-battery transfer (HBX) function used by a MATE3-class system display. However, it is not compatible with HBX and cannot be used at the same time. When using Mini Grid mode, the user should disable HBX to prevent conflicts. Mini Grid mode is also incompatible with the system display Grid Use Time and Load Grid Transfer functions. These functions do not have similar priorities to Mini Grid or HBX, but they do control the inverter’s grid connection and disconnection. Mini Grid should not be used with these functions.
* The Radian inverter will offset the loads with excess renewable energy if it is available from the batteries. Seei nverter manual for more information on Offset operation. However, Offset is inapplicable when the Radian/FXR disconnects from an AC source. The renewable energy supports the inverting function instead.