Battery Technology Overview – Part 1
There are three main types of battery technologies used in laptop computer batteries; the main difference is the chemical structure in which they store the electricity which affects their charging and discharging as well as the maximum voltages able to be held. Nickel cadmium batteries have a nominal cell potential of 1.2 volts, and changes little, if any, as the battery discharges. This makes it difficult to determine the battery’s charge and remaining power. Nickel cadmium batteries have a low internal energy density and have been steadily being replaced by nickel metal hydroxide and lithium ion batteries.
However the nickel cadmium batteries are more durable and can sustain longer storage times as they do not discharge quickly. NiCd batteries can also be charged and recharged more often than their competing alternatives extending battery life. The nickel cadmium batteries are more sensitive to temperature; they lose internal resistance and thus deliver less power in high temperature environments. Nickel metal hydroxide (NiMH) batteries are similar to NiCd in that they are widely used for rechargeable battery applications. The main difference is that the NiMH battery has two to three times the internal capacity of a NiCd battery. Nickel metal hydroxide batteries are well suited to high current drain applications like powering LCD screens.
This is due to their low internal resistance, lower than the NiCd batteries providing more reliable constant high currents. NiMH batteries are also considered to be more environmentally friendly than NiCd batteries due to the lack of toxic cadmium. The use of a hydrogen absorbing alloy allows the batteries to be charged and recharged hundreds of times decreasing the cost of ownership. As opposed to NiCd batteries the NiMH batteries can be charged without the use of a special charger. Manual charging is possible but only if monitored closely and charged at a moderately high rate.
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