I have small toy and it’s not used for three weeks, later I found out one side of the battery holder at (-) negative polarity spring got eroded. I knew battery gets discharged without using the device but how come the chemical reaction occurred and entire spring disintegrated?
- The quality of batteries. Branded batteries can be of bad quality. Be cautious of Panosanic or Sanio batteries;
- Damaged batteries, e.g. the parcel full of batteries have fallen to the floor during transportation, and interior and exterior battery structures get damaged, causing the leak shortly;
- The position of storage. Note that third battery did not leak, because it is located upside down.
The pic of the batteries would help to diagnose the problem better.