Primary Batteries i.e. Non-rechargeable
Zinc Carbon: This battery is nominal 1.5 V, an old type, cheap and voltage varies considerably during use.
Alkaline Manganese: This battery is nominal 1.5V, ubiquitous replacement for zinc-carbon, higher energy more expensive.
Mercury: This battery is phased out in many applications because mercury is very poisonous, was/is used in small applications e.g. cameras, hearing aids.
Lithium: This battery comes in wide ranging family with voltages varying from 1.5 V to 3.6 V, high energy density, voltage almost constant and very long shelf life. Sounds magic and indeed they are special but the downside is that Lithium is a very reactive element, which can lead to explosive consequences. Do not attempt to charge unless explicitly specified and avoid short circuits. They are also very expensive to buy.
Zinc Air: This battery is nominal 1.4V, as its name suggests must be exposed to the air (a seal is usually removed when first used), high self-discharge rate.
Silver Oxide: This battery is nominal 1.55V. Often sold as button cells, for use in calculators, cameras, watches etc where its stable discharge characteristics are valuable.
Secondary - Rechargeable
Lead-acid: This battery is nominal 2 V per cell, as used in cars, well known to be rechargeable, large capacities but lead is very poisonous. This battery can be either wet or dry and its disposal and recycling is easy because the large amount of lead in each battery has a value in the scrap metal industry. Lead-acid and Sealed Lead-acid (SLA) are used where relatively large energy ratings are called for but weight is not a major problem.
Nickel Cadmium (NiCad): This battery is 1.2 V per cell. Used extensively in rechargeable situations and because it exhibits a memory effect is either continuously trickle-charged or recharged after complete discharge (i.e. not partially discharged and then charged). NiCad can be recharged a large number of times (say, more than a thousand). NiCad's may be produced as dry cells or vented units, the manufacturer SAFT has subsidised the recycling of the vented units but this scheme is due to end in December 2003. Cadmium is very poisonous.
Nickel Metal Hydride (NiMH): This battery is 1.2V per cell. They are a new generation that can replace NiCad and have higher energy density and longer life cycle, and don't exhibit memory effect, are usually charged with constant current source. They do not contain the most dangerous heavy metals so are more environmentally friendly than NiCad. The disadvantage is that they cannot be recharged so many times as NiCad (maybe less than a thousand), but this is a theoretical constraint because many NiCad's fail to delivery their optimum number of recharges.
Nickel-zinc: 7 cells for 12V, is claimed to provide the lowest impact to the environment of any standard rechargeable battery technology mainly because of the absence of contamination from the dangerous heavy metals. They have lower cost than NiMH, are lighter and better performers than lead acid, have a high capacity per cycle and high cycle life and they also have low maintenance requirement. Size may be less than Lead-acid and about the same as NiCad.
Lithium Ion (Li-Ion): This battery is used, as well as NiMH, in special applications e.g. laptop computers, are expensive to produce and hence to buy. They have the advantage that they have about twice the energy density of NiCad and NiMH hence can be much lighter and smaller for the same capacity. They can be recharged up to 1000 times approximately. Lithium is a very reactive element, which can lead to explosive consequences, ruptured cells may cause fire and spent batteries should be stored with care.
Lithium Polymer (LI-Polymer): This battery could become the battery of the future. They are reputed to have similar characteristics to Li-Ion but should be much cheaper to produce
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