Batteries leak primarily due to internal chemical reactions that generate gases, causing pressure build-up inside the battery casing. When this pressure exceeds the battery's seal strength, the casing ruptures and releases the internal chemicals. This is most common when batteries are left unused for long periods, are fully discharged, or are subjected to heat or physical damage. The leaking substance in alkaline batteries is potassium hydroxide, a caustic alkaline electrolyte, not an acid as commonly thought.
Reasons for Battery Leakage
- Batteries produce hydrogen gas during chemical reactions that generate power. When batteries sit unused, hydrogen gas can accumulate inside until the pressure breaches the casing seals, causing leakage.
- Fully discharged batteries have more internal pressure because of ongoing chemical reactions, increasing the risk of leakage.
- Exposure to high temperatures or physical damage can rupture the battery casing, allowing leakage.
- Mixing different types or brands of batteries in one device can lead to uneven discharging and increase leakage risk.
What Leaks Out
- In alkaline batteries, the leaking substance is potassium hydroxide, which reacts with carbon dioxide in the air to form potassium carbonate, a white crusty residue.
- Zinc-carbon batteries leak an acidic electrolyte and degrade the zinc casing, causing corrosion and leakage.
How to Avoid Leakage
- Remove batteries from devices that are not used frequently.
- Avoid mixing battery types and brands in a device.
- Store batteries properly in a cool, dry place and avoid extreme temperatures.
- Use sealed, high-quality batteries designed to resist leakage.
In summary, batteries leak because of pressure buildup from chemical reactions inside, especially when they are not used or fully drained. Proper use and storage significantly reduce the risk of leakage.
