Why is my battery not discharging during the evening peak?
If the battery is charged but the house still imports expensive electricity in the evening, the problem is often control logic rather than battery capacity. The exact cause is system-specific, but several settings repeatedly matter.
1. Is the battery in the right operating mode?
Australian Government guidance notes that battery management systems can be configured differently for bill savings, backup or VPP participation, and may need reconfiguration when your electricity plan changes. A system optimised mainly for solar self-consumption, backup reserve or an external energy service may not behave like a simple peak-shaving schedule.
Australian Government battery management guidance →
2. Is a backup reserve stopping discharge?
Many systems preserve a minimum state of charge for backup. Fronius documents a Reserve Capacity setting below which the battery does not discharge in normal grid-connected operation. A high reserve can therefore leave substantial stored energy unavailable for evening peak shaving.
Fronius battery management guidance →
3. Is the time-of-use rule actually commanding discharge?
Some platforms let you define explicit charging and discharging windows. Fronius documents time-dependent battery control with minimum/maximum charge and discharge power rules; GoodWe documents TOU schedules that can charge or discharge at selected times. A schedule that only creates a charging window does not necessarily create an evening discharge window.
Fronius time-dependent battery control → · GoodWe TOU controls →
4. Is another controller higher priority?
OEM systems can have multiple control layers. Fronius states that battery-management rules can be influenced by grid-charging permission, inverter/system power limits, Modbus commands and self-consumption optimisation, and that time-dependent rules may not always be fulfilled when higher-priority controls apply. VPP or retailer control can also deliberately hold, charge or discharge a battery at different times.
5. Can the battery see the household load correctly?
If CTs or meters do not measure the relevant load correctly, the battery may not respond to the household demand you expect. This is a commissioning and system-topology question, not something BecSpec can diagnose remotely.