Ni-Mh

The success of the NI-Mh has been driven by high energy density and the use of environmentally friendly metals. The modern Ni-Mh offers up to 40% higher energy density compared to Ni-Cad. There is potential for yet higher capacities.

The Ni-Mh has been replacing the NI-Cad in markets such as wireless communications and mobile computing. In many parts of the world, the buyer is encouraged to use Ni-Mh rather than Ni-Cad batteries. This is due to environmental concern about careless disposal of the battery.

The question is often asked, " Has Ni-Mh improved over the last few years? " Experts agree that considerable improvements have been achieved, but the limitations remain. Most of the sort comings are native to the Nickel based technology and are shared with the Ni-Cad battery. It is widely excepted Ni-Mh is an interim step to lithium battery technology.

Initially more expensive than the Ni-cad, the price of the Ni-Mh has dropped and is now almost at par value. This was made possible with high volume production. With a lower demand for Ni-Cad, there will be a tendency for the price to increase. 
 

Lithium ( ER )

The energy density of the lithium Iron is typically twice that of a standard Ni-Cad. Improvements in electrode active materials have the potential of increasing the energy density close to three times that of the Ni-Cad. In addition high capacity, the load characteristics are reasonably good and behave similarly to the Ni-cad in terms of discharge characteristics " similar shape of discharge profile, but different voltage". The flat discharge curve offers effective utilization of the stored power in the desirable Voltage spectrum.

The Lithium-Iron is a low maintenance battery, an advantage that most other chemistries Cannot claim. There is no memory, and no scheduled cycling is required to prolong the battery's life. In addition, the self-discharge is less than half compared to Ni-Cad and Ni-Mh, making the Lithium-Iron well suited for modern fuel gauge applications.

The high cell voltage of Lithium-Iron allows the manufacture of battery packs consisting of only one cell. Many of today's mobile phones run on a single cell, and advantage that simplifies battery design. Supply voltages of electronic applications have been heading lower, which in turn require fewer cells per battery pack. To maintain the same power, However, higher currents are needed. This emphasizes the importance of very low cell Resistance to allow unrestricted flow of current. 

Ni-Cad

The Ni-cad prefers fast charge to slow charge and pulse charge to DC charge. All other chemistries prefer a shallow discharge and moderate load currents. The Ni-cad is a strong and silent worker. Hard labor possesses no problem. In Fact the Ni-cad is the only battery that performs best under rigorous working conditions. It does not like to be pampered by sitting in chargers for days and being used only occasionally for brief periods. A periodic full discharge is so important that, if omitted, large crystals will form, ( also referred to as memory.) and the Ni-cad will gradually lose its performance.

Among rechargeable batteries, NI-Cad is a popular choice for applications such as two way radios, emergency medical equipment, professional video cameras and power tools.

The Button cell.

The main applications of the rechargeable button cells are " or were" older cordless telephones, biomedical devices and industrial instruments. Although small in design and inexpensive to manufacture, the main draw back is swelling if charged to rapidly. Button cells have no safety vent and can only be charged at a 10 -16 Hour charge rate. New designs claim rapid charge capability.