NiCd = This is the lowest cost battery but it loses capacity due to "memory effect". NiCd batteries can sit for long periods of time while retaining a charge. For maximum battery life, completely discharge the battery before recharging.

NiMh = (Nickel metal hydride) This battery generally has a greater capacity (30%) than NiCd batteries and does not suffer as much from "memory effect". Storing this battery for more than 3 weeks is not recommended as the battery will discharge quickly. Frequent recharging without completely discharging the battery will not cause "memory effect", however the maximum number of charge cycles is lower than NiCd batteries.

Li-Ion = (Lithium Ion) This battery is very lightweight and does not suffer from "memory effect". It requires a special charger (tri-chemistry) to charge the battery. If you have the proper charger, this battery will be your best choice. It is more costly upfront to purchase, but a longer life with no "memory effects" can offset this initial cost.

Memory Effect - Repeatedly charging a battery builds up a resistance which lowers the batteries maximum capacity. Example: If a 1000mah NiCd battery is charged and discharged every day for one year, at the end of the year it's capacity may only be 850mah. After a 2nd year of usage the battery may be at 700mah etc.

MilliAmp Hours (mah) - Think of this rating as the size of your gas tank. The higher the number the longer you can go without refueling. However, the higher the number the heavier the battery will weigh and cost to purchase. If you're constantly running down your battery before you can recharge, you may need a higher capacity. Otherwise we recommend you keep the same rating as the battery you have been using.

OEM versus aftermarket batteries - For 95% of users, aftermarket batteries are a perfectly fine substitute for OEM batteries. Nearly all batteries (aftermarket and original) are made in Asia, mostly China. The cells used in these batteries either come from Japan or China. Japanese cells are considered superior to Chinese cells in both operating temperature and charge cycles. The plastic case (housing) on most aftermarket batteries is a copy of the original, in both fit and function. The big advantage of aftermarket batteries is cost (about half price of OEM) with little difference in durability or lifespan for the typical user. When operated in extreme environments (hot/cold) or in critical situations (Military) we recommend OEM batteries. For everyone else concerned about cost, we would recommend aftermarket batteries.