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A solar battery that is losing capacity can show up in three places: your monitoring app, your electricity bill, and the length of time it keeps the lights on during an outage. Watch for a lower-than-normal state of charge, sluggish charging speeds, or faster evening run-down. If bills climb even though tariffs and habits have not changed, the battery may not be storing as much solar energy as before. And if backup used to last six hours but now cuts out after three, something is wrong. Confirm the figures against last year’s data, check that inverter settings still match your tariff, and make sure the battery is within its temperature limits. When error codes persist, or the cause is unclear, book a CEC-accredited technician. Timely action maximises self-consumption, safeguards warranties, and keeps the environmental pay-off on track.
How can you tell if your solar battery is underperforming?
Solar batteries are built to deliver a decade or more of service, but even premium units such as Sigenergy’s modular SigenStor or the ever-popular Tesla Powerwall will slowly lose capacity. Some decline is normal; accelerated loss is not. Because a battery sits silently in the background, it can be hard to tell whether today’s performance drop is normal degradation or a fixable fault. This guide explains the tell-tale signs of an underperforming solar battery, what you can investigate yourself, and when to call an expert, so you can keep reaping the financial and environmental rewards of clean energy storage.
Why early detection matters
Underperforming storage erodes solar self-consumption, forces more grid imports, and undermines the return on your investment in renewable energy. Catching issues early protects your warranty rights under Australian Consumer Law, prevents small configuration errors from turning into bigger faults, and ensures you continue to cut carbon emissions.
Spotting the warning signs in your monitoring app
Most modern systems provide granular data through a smartphone portal—solar battery troubleshooting starts here. Focus on four metrics:
- State of charge (SoC). Compare today’s maximum SoC with figures from the same season last year. A healthy lithium-ion unit should still reach its programmed upper limit (often 90– 100 per cent) on sunny days.
- Charge and discharge power. If a 5 kW battery now tops out at 3 kW, something is restricting throughput. Hybrid inverters such as Sungrow’s SH-RT series can flag this in their event logs.
- Daily energy throughput. Sudden dips that cannot be explained by cloudy weather or an extra household load point to a battery or PV issue.
- Error codes. Red flags from the Battery Management System (BMS) deserve immediate attention—consult the manual or your installer before attempting resets.
Tip: Export monthly performance reports and keep them in a cloud folder. Consistent record keeping makes genuine faults stand out clearly.
Clues from your electricity bill and backup time
A subtle signal that your battery is underperforming is a creeping electricity bill. If consumption and tariffs are unchanged but imports rise, the battery may not be supplying its usual evening energy. Households on time-of-use tariffs in NSW or Victoria should pay special attention—wrong discharge windows can add dollars quickly.
Likewise, for homes that rely on backup, measure how long essential circuits run during a blackout. If the original design promised six hours at 2 kW but you now get half that, capacity has slipped, or configuration has changed. Keep a log of each outage; this data helps technicians separate natural ageing from faults.
Common causes of poor battery performance
- Natural degradation. Lithium-ion cells lose roughly 2–3 per cent of capacity each year. Warranty documents usually guarantee at least 60–70 per cent of the original capacity after ten years or a set number of cycles.
- Mis-configuration. A firmware update can reset depth-of-discharge limits or tariff schedules. Check settings after major software releases.
- Temperature extremes. Prolonged operation above 40 °C, common in uninsulated Perth garages, can throttle performance and accelerate wear. Adequate ventilation or a shaded enclosure is vital.
- PV issues upstream. Dirty or shaded panels cannot deliver enough energy to fill the battery. Panels with advanced hotspot-mitigation, such as AIKO’s half-cut, high-efficiency modules, reduce shading losses but still need occasional cleaning.
- BMS or cell faults. Rare but serious, these require professional diagnostics and may trigger warranty replacement.
What you can safely check yourself
- Dive into the data. Use your monitoring portal to graph SoC, charge power, and PV production over several sunny days. Look for patterns rather than single-day anomalies.
- Review inverter settings. Ensure time-of-use discharge windows and DoD limits match your tariff and manufacturer guidelines. If uncertain, document current values and leave changes to your installer.
- Inspect the installation environment. Confirm ventilation grills are clear, the unit is dry, and no external heat sources are nearby. Feel for excessive warmth (without opening the casing).
- Assess PV output. Compare current kWh production on a clear day with historical data. If generation is down, clean panels or trim shading vegetation—seek advice before tree removal and replant where possible.
- Keep a performance diary. Note dates, weather, SoC highs and lows, error codes, and any unusual noises. Clear, time-stamped evidence speeds up professional troubleshooting.
When to call a CEC-accredited professional
Contact your original installer—or another Clean Energy Council-accredited electrician—if any of the following apply:
- Error codes persist or reappear after basic resets.
- Battery runtime or capacity drops sharply (for example, below warranty thresholds).
- You detect unusual sounds, smells, or heat.
- Configuration checks reveal no obvious cause for a performance dip.
- The battery is within its warranty period, and you need formal test results to lodge a claim.
Trained technicians carry specialised testing equipment, can balance cells, flash new firmware, verify compliance with AS/NZS 5139 and AS/NZS 5033, and ensure the installation still qualifies for incentives such as STCs or upcoming Federal battery rebates.
Keeping your battery working at its best
- Regular monitoring. Set a calendar reminder to review performance every quarter.
- Environment control. If temperatures regularly exceed the battery’s comfort zone, consider adding shading or ventilation.
- Software updates. Schedule updates at off-peak times and read release notes for changed defaults.
- Plan for growth. If you add high-load appliances or an EV, revisit battery sizing. Modular products like Sigenergy’s SigenStor let you add extra 5 kWh blocks instead of replacing the whole unit.
- Stay accredited. Use CEC-approved installers and components to keep warranties intact and meet DNSP requirements when upgrading.
Conclusion
A high-performing solar battery is the cornerstone of maximising solar self-use, shielding against rising power prices, and cutting household emissions. By tracking key performance indicators, understanding common causes of decline, and knowing when to engage a professional, you maintain both savings and peace of mind. If you are unsure whether your battery is underperforming—or need a trusted expert to diagnose an issue—Your Energy Answers can connect you with qualified, local specialists.
