Why does my battery only charge from solar?

That may be the intended operating mode. Solar self-consumption and tariff arbitrage are different control strategies. A system configured to maximise solar use may wait for daytime excess PV instead of charging from the grid overnight.

Solar self-consumption mode

Australian Government guidance describes the common pattern: excess rooftop solar charges the battery, then stored energy is used later when solar output is low. That strategy does not require overnight grid charging.

Tariff optimisation mode

With a time-of-use tariff, some systems can also charge from cheap grid electricity and discharge during expensive peak periods. Solar Victoria explicitly notes that overnight grid charging requires the right battery functionality and smart software; Australian Government guidance likewise recognises grid charging for tariff arbitrage.

Solar Victoria overnight charging guidance → · Australian Government tariff arbitrage →

What can prevent grid charging?

The battery may be in self-consumption rather than TOU mode; grid charging may be disabled; the configured off-peak window may be wrong; the battery may already be at its target SOC; or another EMS/VPP rule may have priority.

Why not just fill it every night?

Because overnight grid energy occupies storage that might otherwise absorb excess solar the next day. A good tariff strategy may deliberately grid-charge only enough to cover an expensive morning or evening period, especially when tomorrow's solar forecast is strong.