Why is my battery always full and not doing anything?

A battery that spends sunny weeks pinned at 100% means your surplus far exceeds what the battery shifts into the night — common in summer, and usually amplified by conservative settings: charging first thing in the morning, or a high overnight reserve. It is not broken, but it is not earning either, and combined with an export limit it can quietly waste real energy.

Why this happens

In peak season a typical array can refill a home battery before noon. If the inverter’s default strategy is “battery first”, it tops up in the morning hours — exactly when you could still be exporting at decent value or running loads directly — and then sits full while the afternoon surplus exports anyway. The battery ends up cycling a fraction of its capacity, contributing little.

The costly variant: with an export cap (common in UK and Australian connections), a full battery removes the only escape valve for above-limit production, and the inverter curtails instead. Those kWh are simply lost. There is also a battery-health angle — lithium cells age fastest held at 100% in heat, so a summer at full charge is the worst resting state you can pick.

What to do

1. Delay battery charging into the midday peak — most hybrid inverters can prioritise loads and export in the morning and fill the battery from the surplus that would be clipped or poorly paid.
2. Drop the overnight reserve — a 30–40% floor made sense for blackout fears; if outages are rare where you live, a 10–15% floor puts more capacity to work daily.
3. With an export limit, choreograph against the forecast — leave enough empty battery to swallow the above-cap production window; a per-system forecast tells you each morning how big that window will be.
4. Consider whether the battery is simply oversized — if it is full year-round even after retuning, the sizing answer is worth a re-read before you add more panels to “fix” it.