The Disadvantages of Nickel Metal Hydride Batteries
What are the Limitations to the Nickel-Metal-Hydride Battery?
• Limited service life - the performance starts to deteriorate after 200-300 cycles if repeatedly deeply cycled.
• Relatively short storage of three years. Cool temperature and a partial charge slows aging.
• Limited discharge current - although nickel-metal-hydride is capable of delivering high discharge currents, heavy load reduces the battery’s cycle life.
• More complex charge algorithm needed - nickel-metal-hydride generates more heat during charge and requires slightly longer charge times than nickel-cadmium. Trickle charge settings are critical because the battery cannot absorb overcharge.
• High self-discharge - typically 50% higher than nickel-cadmium.
• Performance degrades if stored at elevated temperatures - nickel-metal-hydride should be stored in a cool place at 40% state-of-charge.
• High maintenance - nickel-metal hydride requires regular full discharge to prevent crystalline formation.
Nickel-cadmium should be exercised once a month, nickel-metal-hydride once in every 3 months.