Batteries available in the market are usually classified as primary batteries and rechargeable batteries.

   Primary Batteries

are sometimes called "throw-away" batteries because they will be discarded when they are flat, as they cannot be recharged for reuse. Common types of primary batteries include alkaline, zinc carbon, lithium, silver oxide and zinc air batteries.

   Rechargeable Batteries

can be recharged and reused for up to 1000 times depending on usage conditions. Common types of rechargeable batteries include Nickel Metal Hydride (NiMH), Nickel Cadmium (NiCd) and Lithium Ion (Li-ion) batteries.

You may have come across terms like "heavy duty", "super heavy duty", and "longer lasting". However, they do not necessarily reflect the service time of batteries, as battery performance depends very much on intrinsic qualities.

Despite the higher initial cost, alkaline batteries last five to ten times longer than zinc carbon batteries on higher current drains, making it more economical when the current drain is high. Rechargeable batteries are more expensive than alkaline batteries especially when you include the upfront cost of the charger. However do not forget that they can be recharged up to 1000 times. Hence they end up much more economical in the long run.

NiCd and NiMH batteries display similar characteristics, but for the same size, NiMH batteries can double the run time compared with NiCd batteries per charge.

Trickle charge refers to an extremely low charging current that is enough to keep the batteries in fully charged condition but without overcharging the battery.

Fast chargers and slow chargers have their respective merits and demerits. You should choose a charger that meets your performance and cost requirements.

A fast charger delivers speed, but its design is more complicated, and therefore is usually more expensive than a slow charger. Overcharging can shorten a NiMH battery's cycle life. Hence a well-designed fast charger has to incorporate certain protection mechanisms that prevent the batteries from being overcharged.

These protection mechanisms, ranging from sophisticated voltage detection to temperature monitoring and timer control, can be expensive. Normally a fast charger has to incorporate at least one of these mechanisms. The more mechanisms it has, the better the protection and thus the higher the price. Therefore, when charging speed is not a priority, it would be more cost effective to select a slow charger, which also gives longer battery service life and enables fuller charge of a battery compared with a fast charger.

However, for applications that require fast charging speed, e.g. remote control racing toy car and digital cameras, it would be worthwhile to invest more for a fast charger to ensure continuous supply of energy.