Every battery wears out. The only question is when, and what you should do about it. Replacing a battery too late risks a failure at the worst moment, such as a power cut. Replacing it too early wastes money. These signs and checks help you decide.
Key takeaways
- Falling backup time, swelling, leaks, heat and age are the main warning signs.
- A capacity test or a load test tells you more than the voltage alone.
- Replace all batteries in a series string together, with the same type and age.
- Recycle the old batteries properly.
1. Warning signs
- Shorter runtime: the UPS or inverter lasts much less than it used to.
- Age: the battery has reached or passed its design life. Look at the date code.
- Physical signs: a swollen case, cracks, leakage, corrosion on terminals or a hot battery.
- Voltage collapse: the voltage drops fast when the load is applied.
- Alarms: the UPS reports a battery fault, replace-battery or failed self-test.
2. Testing
Voltage with no load tells little, since a weak battery may show normal voltage and then collapse. A proper test applies a load and measures the voltage and the time, or uses a battery tester for internal resistance or capacity. Many UPS units have a self-test; run it regularly and keep the results.
3. Design life and real life
Design life is quoted at 25 °C; heat, deep discharge, poor charging and long storage reduce it. A battery in a hot room may need replacing years earlier than the rating. Read temperature and battery life.
4. Replace as a set
In a series string, one weak battery limits the rest and wears them. Replace the whole string with batteries of the same type and size, from the same batch, so they age together. Do not mix old and new, which is covered in battery safety.
5. For solar and hybrid systems
If the battery no longer reaches full charge, drops quickly or shows a large loss of capacity in the app, it is ageing. Compare the capacity with the warranty terms; a battery that falls below the guaranteed level may be covered. See depth of discharge and battery life.
6. Disposal
Used lead-acid and lithium batteries must not be thrown away with household waste. Ask your supplier to take back the old ones for recycling, which is the common practice for lead-acid batteries.
Next step
If your UPS or solar battery shows the signs above, we can test it and quote a replacement; contact us through the contact page or see our repair service.
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