A Nickel Metal Hydride Battery charger or more commonly known as NiMH battery charger is an improvement over the traditional battery chargers. They can be recharged a lot of times, have a longer life and are way more environment friendly than the counterpart viz. NiCad batteries. A NiMH Battery charger is called a smart charger as they assess the remaining battery life, the required voltage for recharging and charges the battery accordingly. It uses the method of ‘trickle charging’ to avoid the battery from deplenishing once it is completely charged.
There are various questions regarding the selection and usage of a NiMH battery charger.
What’s the difference between a NiMH battery charger and a NiCad battery charger?
The biggest difference is in the charge rate (how fast the charger can charge batteries) and the charge control (how the charger determines when to stop the charge). Many of the inexpensive NiMH battery chargers are simply NiCad battery chargers that have been modified slightly. Typically a 5 hour NiCad charger has a switch that allows the charge time to be increased from five hours to eight hours. Thus a 5 hour NiCad battery charger becomes an 8 hour NiMH battery charger. While a timer type charger is less expensive to manufacture than a standard NiMH battery charger, it can lead to overcharging and damages the battery if they are frequently charged before they have been discharged (that is, the batteries are used for a short time and then fully charged again).
A NiMH smart charger has actually been designed to detect when a NiMH battery is fully charged and then shut off or go into the trickle charge mode. Because of the more complex NiMH charger circuit, this type of charger costs more, but also leads to greater battery life. It is recommended to invest in a smart charger for your NiMH or NiCad batteries.
Which are better, NiCD or NiMH batteries?
This really depends on what you are going to use them for exactly. NiCD batteries are commonly used for power tools and in that capacity they are in many ways superior to NiMH batteries. For high drain digital devices where weight is of primary importance, NiMH batteries are the best choice. NiMH batteries are also considered environmentally friendly. NiCad’s are toxic and recycling them is mandatory.