NiMH and NiCD batteries serve the same purpose but have different properties.
People rely heavily on electronic devices. Even the kids' aisles in department stores are filled to the brim with items that are useless without power. As a result, people have a huge need for batteries. Two primary types of batteries are NiMH and NiCD. There are differences between these two battery types that indicate how a battery owner should handle them. Failure to recognize these differences can damage the batteries or cause injury.
Contents
The primary difference between NiMH batteries and NiCD batteries is the material that makes them up. NiMH stands for nickel metal hydride, while NiCD stands for nickel cadmium. The metal hydride or cadmium in each type of battery is what makes up the negative electrode in the battery. Nickel oxyhydroxide makes up the positive electrode in both battery types. It is these different components that produce the different properties of the batteries.
Duration and Charge
NiMH batteries have more than twice the storage capacity than NiCD batteries, according to maxwellcanada.com. NiMH batteries aren't equipped to handle high charge and discharge rates--more than 1.5 to 2 amps--the way NiCD batteries are, according to Servocity.com. This means that NiMH batteries are the better option for electronics that don't have high amp requirements but which need to operate for the long haul. The discharge rate for NiMH batteries is at least twice as fast as an NiCD battery, according to greenbatteries.com. Thus, a user may need to charge their NiMH battery more often than a NiCD battery.
Chargers
Because NiMH and NiCD batteries are chemically different, they cannot use the same type of charger. NiMH batteries need more sophisticated chargers than NiCD batteries, according to Servocity.com. The high rate, peak detection or time-based chargers people use with NiCD batteries can overcharge NiMH batteries and damage the battery cells.
Memory
There technically is no such thing as "memory" with a battery. However, there is voltage depletion or depression, which some people refer to as the memory effect, according to greenbatteries.com. NiCD batteries sometimes experience voltage and capacity dips when they are recharged without being fully depleted. As a result, the battery can't provide as much power or doesn't last as long. NiCD batteries thus have to be "conditioned" by fully draining them prior to recharging. NiMH batteries don't suffer from the memory phenomenon. A user can safely "top off" a NiMH battery and not worry about conditioning the battery improperly.
Environment
Cadmium is considered much more hazardous to the environment than metal hydride. As a result, NiMH batteries are considered safer than NiCD from an ecological standpoint, according to maxwellcanada.com.
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