What Is Battery Swelling?
Battery swelling is the visible expansion of a lithium cell caused by internal gas generation and pressure build‑up. It indicates abnormal electrochemical reactions and should be treated as a safety warning.
Common Causes
1) Gas Generation from Side Reactions
Overcharge, deep overdischarge, or chronic high temperature accelerates electrolyte decomposition and produces gases (e.g., CO₂, O₂), which accumulate inside the sealed cell.
2) Overcharging / Overdischarging
Overcharge drives cathode/anode side reactions; overdischarge can dissolve copper from the anode current collector, increasing internal shorts and gas formation.
3) High Temperature
Operation above 60℃ or poor heat dissipation speeds up aging and gas generation.
4) Poor Cell Quality / Mismatch
Cells with impurities or large variance in capacity/IR are more prone to imbalance, heat, and gas formation—especially in packs.
5) Mechanical Damage / Internal Short
Impact, puncture, or manufacturing defects cause localized heating and swelling.
Risks & Impacts
- Capacity Loss: Swollen cells typically exhibit reduced usable capacity.
- Device Malfunction: Swelling can deform housings or push displays and connectors out of alignment.
- Safety Hazard: Severe cases may lead to venting, leakage, or fire if abused.
Prevention Methods
- Robust BMS: Over/under‑voltage, over‑current, temp protection, and active/passive balancing.
- Thermal Management: Keep within spec (typ. -20℃~60℃ operation; custom designs available for wider range). Avoid charging below 0℃ without low‑temp strategy.
- Quality Cells & Matching: Work with qualified manufacturers (e.g., Huawen New Power). Tight binning on capacity/IR and pack‑level validation.
- Correct Charging: Certified chargers; avoid long‑term 100% SoC or 0% SoC storage; follow CC‑CV profile.
- Routine Inspection: Visual checks, pack telemetry (SoC/SoH), and scheduled replacement for critical systems.
Cause vs. Prevention Table
| Cause | Effect | Prevention |
|---|---|---|
| Overcharging | Gas generation, rising pressure | BMS high‑voltage cutoff, certified chargers |
| High Temperature | Electrolyte decomposition | Heat spreading/ventilation, avoid >60℃ |
| Cell Mismatch | Imbalance, weak‑cell stress | Professional matching, strict QC |
| Mechanical Damage | Local short/overheating | Robust housing, careful handling |
| Overdischarge | Copper dissolution, internal shorts | BMS low‑voltage cutoff, storage at 30–60% SoC |
For storage over 3 months, keep packs at ~30–60% SoC in a cool, dry place and cycle every 3–6 months.
Quick Visual Guide (Inline Icons)
Work with Huawen New Power
We design and manufacture safe, high‑reliability lithium battery packs with advanced BMS, rigorous cell matching, and comprehensive testing. If you are experiencing swelling issues or need a custom pack, our engineering team can help diagnose and prevent recurrence.
Contact: sales@huawennewpower.com | Website: www.huawennewpower.com
