Nickel-Cadmium Batteries
Mechanism
Nickel-cadmium batteries are secondary batteries, which use a solution of potassium hydroxide as the electrolyte, nickel hydroxide as the cathode and cadmium as the anode. This is one of the oldest rechargeable batteries, however, their continued use is due to the fact that they are robust and safe generators.
Capacities and life cycle
These are characterised by the fact that they admit overcharges, that is to say, they can continue to be charged when it no longer admits charging but does not store this excess, in addition to the fact that they admit a wide range of temperatures for their operation, the repetition of charge and discharge cycles progressively destroys the internal structure of the battery so that its useful life is limited to approximately 500 complete charge and discharge cycles. The useful life can be extended if the battery is never discharged below 50% and over-discharges are avoided, reaching 1500 cycles under these conditions. In any case the useful life will depend on the conditions of use.
Applications
These generally have an economic price that is around 155 $ per kWh, these are usually used in a wide variety of applications within industry and the home.
Advantages
Advantages include a wide range of sizes and performance options, can be stored discharged, are less likely than normal batteries to lose electrolyte, maintain near constant voltage for nearly 90% of the discharge cycle, can be recharged quickly, have extremely low internal resistance and have good low temperature performance.
Disadvantages
Among the disadvantages is that they have 20% less voltage compared to normal batteries, due to its low internal impedance can not be charged at constant voltage because they would generate very high currents that produce the heating of this which can lead to its destruction, have memory effect, ie when recharging a battery that is not fully discharged, there can be a temporary loss of charge which causes the cadmium to crystallize which reduces the area exposed to the electrolyte resulting in a decrease in performance and finally, when it reaches the end of its useful life should be considered that cadmium is a toxic material so it can not be disposed of in landfills, so it is expensive to waste it.