How to Tell if a Battery Needs a Warranty Claim

Not every battery issue is grounds for a warranty claim. But some are. Here is a guide on how to tell the difference — and how to prepare documentation so your claim gets approved.

When a Warranty Claim is Justified

1. SOH below 80% during the warranty period

Pylontech guarantees a minimum of 80% capacity for the duration of the warranty (typically 10 years or 6,000 cycles). If SOH drops below 80% earlier, you are entitled to a warranty claim.

The problem: The SOH shown by the BMS is not always accurate. The BMS calculates SOH based on an internal algorithm and sometimes displays 100% even for a battery that is actually at 85%. That's why it is important to monitor other indicators as well.

2. Persistent Imbalance above 200 mV

If one cell permanently has 200+ mV more or less than the others and balancing doesn't fix it even after a week, it is a defective cell. This is a manufacturing defect or premature degradation.

3. Cell with Zero Voltage

If you see a cell at 0 mV or below 2000 mV while the others are at 3300+ mV — it is dead. An internal short circuit or broken connection.

4. Battery is Not Charging/Discharging Even at Normal Temperature

If the temperature is within normal limits (15–35 °C), SOC is not at its limit, and the battery still refuses to charge/discharge — the BMS electronics may be defective.

When it is NOT Grounds for a Warranty Claim

• Imbalance of 50–100 mV after 2 years of operation — this is normal aging
• Reduced capacity in winter — this is physics, not a defect
• Alarm after an overvoltage from the inverter — this is an installation error, not a battery fault
• SOH 90% after 3 years — this is within normal limits

How to Prepare Documentation

Distributors don't care about "the battery doesn't work". They care about:

• Serial number — precise battery identification
• Date of manufacture — from the info command or label
• Firmware version — essential for assessment
• Cycle count — how many charge/discharge cycles the battery has completed
• Voltage of all cells — proof of imbalance or a defective cell
• Alarm history — what the BMS reported
• Temperatures — proof that the battery was not operated outside of specifications

Warranty Claim Report from PylonCheck

That is exactly why we created the "Warranty Claim Report" feature. With a single click, you can generate a PDF document with all the necessary data:

• Battery identification (SN, model, FW, date of manufacture)
• Current status (SOC, SOH, cycles, temperature)
• Voltages of all cells with problem cells highlighted
• Health Score (0–100)
• Alarm history
• Recommendations

Send this to the distributor, and you have a 90% chance of getting the claim approved. Without data, it's just your word against theirs.

Final Tip

Start monitoring batteries AS SOON AS POSSIBLE — ideally right after installation. If you file a claim in 2 years, you will have a complete history. Without history, it is difficult to prove that the problem is a manufacturing defect rather than misuse.