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Battery Types

Ni-Cad (Nickel Cadium)

The basic voltage for Ni-Cads is 1.25V which makes them unsuitable for certain applications. The number of times they can be recharged is also limited, bad charging habits reduce this even more.

The main problem with Ni-Cads is the dendrite growths, miniature metal spikes which eventually short circuit the cell. This can be reduced by PCR charging.

Self discharge rate is 1% per day.

The lifetime is approx 1000 recharges in a cellular phone battery.

Ni-MH (Nickel Metal Hydride)

This newer rechargeable cell is free from toxic elements such as cadmium, they have around 30 to 50% more capacity than good Ni-Cad cells. They cost about twice as much as Ni-Cads, but have a shorter service life, up to 500 cycles compared with 1000 for Ni-Cad. They also have the same voltage per cell as Ni-Cads that is 1.25V per cell.

They use hydrides (metals capable of storing hydrogen) as the negative material in lieu of cadmium. They have higher capacity for the same size cell, and don't use toxic cadmium. They also are advertised as not suffering from memory.

They are trickier to charge. Delta V works, but the voltage drop is very small (2.5 mV/cell).It is far better to charge them to a point where the voltage stops rising.

They still suffer from memory effect, but it is much harder to see then it is with Ni-Cads.

Self discharge rate is 3 to 10% per day.

The lifetime is approx 500 recharges in a cellular phone battery.

Li-Ion (Lithium Ion)

No Memory effect is evident with these batteries, any problems with these cells can normally be contributed to poor charges and poor charging techniques.

Li-Ion batteries are VERY light.

Self Discharge is 1 to 2% per month.

The lifetime is approx 300 to 500 recharges in a cellular phone battery. This figure varies a lot as they are still really being developed and early batteries did not last very long.