Self-Discharge

• The amount of humidity, which is the percentage of water vapor contained in air, accelerates a NiCd batteries self-discharge rate. All NiCd batteries self-discharge over time, but the higher the percentage humidity the faster the battery will go dead.
  
  

Temperature

• If you combine humidity and heat you can expect a NiCd battery to possibly go dead inside one month. NiCd batteries exposed to a temperature higher than about 80F discharge quickly; the higher the temperature the quicker the discharge so even if the humidity isn't too high your battery will go dead.
  
  

Low Humidity

• Dry environments where the humidity level is less than 50 percent slows the self-discharge rate of a NiCd battery. In the correct humidity conditions, an NiCd battery will still power an electrical device even if it's stored unused for a year.
  
  

Effect 4

• With humidity below 20 percent and the temperature below 40F, a stored and charged battery will retain its charge even longer. Storing the battery in a dark place assists even more. A battery stored under these conditions will retain its original chemical composition inside the cell.