Swollen Battery Survival Guide: How to Test Salvageability with a Multimeter
Swollen drone batteries pose fire risks and performance issues, but not all are beyond repair. Using a multimeter, you can determine if a puffed battery is safe to reuse or must be recycled. This guide explains how to diagnose swollen batteries step-by-step, balancing safety and cost-efficiency.
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1. Initial Voltage Check
Set your multimeter to DC voltage and measure the battery’s terminals. A healthy lithium battery should read 3.0V–4.2V per cell.
Salvageable: If voltage is 3.3V–4.1V, proceed to further tests.
Critical Risk: Below 3.0V indicates severe degradation—dispose immediately.
2. Internal Resistance Test
Switch the multimeter to resistance mode (milliohms). Connect probes to the battery’s positive and negative terminals.
Safe Range: ≤50mΩ per cell (e.g., 150mΩ for a 3S battery).
Unsalvageable: >100mΩ signals damaged electrodes or separators.
3. Load Test for Stability
Attach a 2C load (e.g., 10A for a 5000mAh battery) for 30 seconds. Monitor voltage drop:
Stable: Voltage dips <0.3V and recovers quickly.
Unstable: Drops >0.5V with slow recovery—discard the battery.
4. Check for Self-Discharge
Leave the battery unused for 24 hours, then remeasure voltage.
Salvageable: Voltage loss <0.05V.
Faulty: Loss >0.1V indicates internal short circuits.
Why Swelling Occurs
Gas buildup from overcharging, deep discharges, or aging damages cell integrity. For example, a 4S battery stored at 100% charge for months often swells due to electrolyte decomposition.
When to Stop Testing
Physical Damage: Leaks, cracks, or hissing sounds.
Heat Generation: Warmth during testing signals thermal runaway risk.
Odors: Chemical smells indicate electrolyte leakage.
Conclusion
A multimeter is your best tool to evaluate swollen drone batteries. If voltage, resistance, and load tests pass, cautiously reuse the battery with frequent monitoring. Otherwise, recycle it responsibly. Never gamble on questionable cells—safety always comes first.
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