Published on June 26, 2025 | By EV Battery School
Introduction
Swollen lithium batteries are a serious safety concern for ebike users. This article will walk you through identifying a swollen battery, understanding the causes, and how to respond safely and effectively.
What Causes a Lithium Battery to Swell?
- Overcharging or poor BMS (Battery Management System)
- Excessive heat exposure
- Manufacturing defects or internal short circuits
Signs of a Swollen Ebike Battery
- Bulging battery case or housing
- Difficulty installing/removing battery from the ebike
- Decreased performance or fast discharge
Is It Safe to Continue Using a Swollen Battery?
No. A swollen battery can explode or catch fire. It should be handled with extreme caution and replaced or repaired immediately.
How to Safely Handle and Fix It
- Power off your ebike completely and unplug the battery.
- Do not puncture or press on the battery case.
- Place the battery in a fireproof container (like a metal box or LiPo bag).
- Use a multimeter to measure cell voltages — any unbalanced cell could be the cause.
- Consult a professional for repacking the battery or replacing swollen cells.
When to Replace the Battery Entirely
If the swelling is severe or involves multiple cells, replacement is safer than repair. Read this guide on battery repair vs. replacement →
How to Prevent Battery Swelling in the Future
- Charge only with compatible chargers
- Avoid charging in hot environments
- Never leave the battery charging overnight unsupervised
- Perform monthly checks using a multimeter
Conclusion
A swollen lithium battery is a warning sign. Don’t ignore it. Whether you’re performing the fix yourself or replacing it entirely, safety comes first.
Want to learn more? Check out our full Battery Repair Guides and download our free EV battery cheatsheet.
📌 Tags: swollen battery, ebike repair, lithium fix, battery safety, battery diagnosis
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