Racing battery packs are specially selected to ensure that they are 'matched'. This means that they will all discharge their capacity at the same rate and at the same time. Each battery pack is made up of individual cells, it is these cells that are matched to make up the whole pack.

NiCd (Nicad)

These are probably the most widely used RC model batteries. Nickel-Cadmium rechargeable batteries are very durable and reliable. You may slow or fast charge most NiCd's, but some manufacturers make different types of cells specifically for rapid charging or specifically for slow charging. NiCd battery performance is improved dramatically by interspersing discharge pulses between charge pulses. This is known as "burp" or "reverse load" charging. This method of charging allows the battery to more efficiently degass while charging.

NiCd batteries should not be left in a charger for more than 30 hours. Also, NiCd batteries should not be subjected to shallow discharge (i.e. using the battery for a short period of time, then recharging). This type of use may result in crystalline formation inside the battery which will diminish performance. This is known as the "memory effect".

NiMH

Not so widely used. Nickel-Metal Hydride rechargeable batteries are the next level up from NiCd. They offer up to 40% more run time per volume than NiCd. They are also more environmentally friendly. The biggest advantage of NiMH over NiCd is their ability to accept a charge at any time without suffering from the "memory effect". The best way to charge NiMH batteries is either with the "burp" charging described above, or with a Delta V terminating charger. Before charging your NiMH battery, check with the charger manufacturer to make sure their charger can handle NiMH.

Li+

Lithium Ion is the latest technology in rechargeable batteries for portable equipment. They have the highest energy density among commercial batteries; twice that of NiCd. They also have a very low self-discharge rate.

Li-Ion batteries are the most expensive batteries available commercially. Disposal of lithium based batteries may cause some concern since any moisture which may creep into the cell after corrosion could present danger of explosion.