How Do I Know If My Solar Battery Is Bad?

Knowing when your solar battery is no longer performing as it should is crucial to protecting your return on investment, ensuring consistent energy savings, and making informed upgrade decisions.

In this guide, we’ll walk you through the tell-tale signs of a failing solar battery, why performance matters, and what you can do about it.

How Can You Tell If Your Solar Battery Is Going Bad? 6 Key Signs to Look For

Recognising when your solar battery is underperforming can help you take proactive steps to resolve issues before they impact your energy system. Here are the most common warning signs:

1. Reduced Storage Capacity

One of the clearest indicators of battery degradation is a noticeable drop in how much energy your battery can store. If your battery used to power your home through the night but now struggles after a few hours, it may be a sign the cells are losing their capacity.

2. Inconsistent Power Output

A healthy solar battery should deliver a steady stream of power. If you're noticing flickering lights, appliances shutting down unexpectedly, or inconsistent energy supply, it could point to a battery problem.

3. Longer Charging Times

A faulty battery may take significantly longer to charge. This may be caused by internal resistance increasing due to cell degradation. If your battery isn’t reaching full charge even on sunny days, it’s time to investigate.

4. Visible Physical Damage or Swelling

Any visible signs of damage, corrosion, bulging or leaking are red flags. A swollen battery, especially lithium-ion, can pose serious safety risks and should be replaced immediately.

5. Error Codes or Alerts from Your Monitoring System

Most modern solar systems come with a monitoring dashboard or app. These systems often flag performance issues or display error codes when your battery isn't functioning correctly. Check your manufacturer's manual or dashboard for guidance.

6. Shortened Discharge Time

If your battery seems to drain far quicker than usual, even under the same usage conditions, this is a common symptom of capacity fade.

What Causes a Solar Battery to Go Bad?

Several factors influence the health and longevity of a solar battery, including:

Overcharging and Deep Discharging

Both lead-acid and lithium-ion batteries degrade faster when frequently overcharged or completely discharged. Using a battery management system (BMS) helps mitigate this risk.

Temperature Extremes

UK weather isn’t extreme, but cold winters and unexpected summer heatwaves can affect battery efficiency. According to the , storing batteries in an insulated, indoor environment like a utility room or garage can help maintain optimal performance.

Poor Installation or Maintenance

Improper wiring, low-quality components, or lack of ventilation can reduce lifespan. Always choose MCS-certified installers.

What Steps Can You Take If Your Solar Battery Is Failing?

If you suspect your solar battery is going bad, here’s what you should do:

1. Check Your Monitoring System

Your first step should be checking the data available via your solar battery’s monitoring software or app. Look for alerts, abnormal charging patterns, or sudden drops in capacity.

2. Schedule a Professional Inspection

Engaging a certified technician can help identify issues and recommend the right solution, whether it’s recalibration, repair, or replacement.

3. Check Warranty Coverage

Most solar batteries come with warranties of 5 to 10 years. If you’re within your warranty window, contact your installer or manufacturer to check eligibility for repair or replacement.

Can a Faulty Solar Battery Affect Your Entire Solar Panel System?

Yes, a degraded or malfunctioning solar battery can compromise the performance of your entire system. 

While your panels will still generate electricity during daylight, a bad battery limits your ability to store and use that energy efficiently, especially during the evening or cloudy periods.

If your battery consistently underperforms, you may find yourself relying more on grid electricity, which diminishes the financial and environmental benefits of your system.

This is especially important as electricity prices continue to rise. 

How Do You Prevent Your Solar Battery From Going Bad Prematurely?

Preventative maintenance is key. Here’s how to keep your battery healthy:

• Avoid deep discharges: Repeatedly discharging a battery to 0% shortens its lifespan.
  
• Maintain moderate temperature: Batteries function best between 15°C and 30°C.
  
• Install in a ventilated space: Proper airflow reduces overheating risk.
  
• Annual servicing: Get your system checked by a qualified engineer.
  
• Monitor performance regularly: Catch minor issues early using your monitoring system.

Tip: The Microgeneration Certification Scheme (MCS) provides accreditation for certified solar and battery installers in the UK. Always choose an MCS-certified provider to ensure compliance with best practices.

Is a Bad Solar Battery Dangerous?

Yes, particularly in older or neglected systems. Issues like:

• Thermal runaway in lithium-ion batteries
  
• Gas buildup in lead-acid batteries
  
• Acid leakage or corrosion

...can pose fire or chemical hazards. That’s why routine maintenance is key. 

When Should You Replace Your Solar Battery?

Most solar batteries last between 10 and 15 years, depending on their type and usage. If you’ve noticed any of the signs above and your battery is approaching the end of its expected lifespan, it may be time to invest in a replacement.

You can also check the battery’s performance through your inverter monitoring app or system dashboard. Some systems will display battery efficiency or even issue alerts when performance drops.

Pro Tip: If your battery’s storage capacity drops below 60% of its original rating, replacement is often more cost-effective than trying to repair or maintain it.

What Are the Costs of Replacing a Solar Battery in the UK?

Solar battery replacement costs in the UK vary based on size, type, and brand. Here’s a rough guide:

FAQs

1. What happens if I don’t replace a faulty solar battery?

If you don’t replace a failing battery, you may lose the ability to store and use solar energy when you need it most. It can also place unnecessary strain on the rest of your system.

2. Are solar batteries safe when they start to degrade?

Degraded batteries can pose safety concerns, particularly if they are physically damaged or swollen. Always consult a professional if you notice these signs.

3. Can I upgrade just the battery and keep my existing solar panels?

Yes. Many homeowners upgrade their battery storage systems without changing their panels. Just ensure compatibility with your existing inverter and system specs.

4. Does the UK climate affect solar battery lifespan?

Yes, extreme cold or heat can impact performance. However, proper insulation and temperature control can help mitigate these effects.

5. Is there any government support to help with battery replacement?

Some schemes, like the ECO4 scheme, may cover solar and battery upgrades for eligible households. Always check current eligibility criteria.

Our Verdict

Spotting the signs of a bad solar battery early can save you money, protect your energy efficiency, and ensure your system continues to deliver strong returns. From inconsistent power to visible damage, being proactive is key.

If you're concerned about your solar battery's performance or thinking of upgrading your system, Eco Answers' free quote-comparison tool makes it easy to connect with trusted UK providers and find the best deal for your needs.

Investing in quality battery storage and proper maintenance today ensures long-term energy security tomorrow.