Batteries 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. Manufacurer of primary batteries are using 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. 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. 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. Both overcharging and over discharging the batteries will result in poor battery performance. Generally speaking, slow charging would lead to longer cycle life than high rate charging. Don't leave your rechargeable NiMH or NiCd batteries discharged or unused for extended periods of time. To keep batteries fresh, charge them at least every 6-9 months. Because of their relatively rapid self-discharge (1% to 3% of capacity per day), remember to recharge your battery a few hours before you want to use it. The Low Self-Discharge NiMH Battery (LSD NiMH) was introduced in November 2005. It reduces self-discharge and, therefore, lengthens shelf life compared to normal NiMH batteries. By using a new separator (usually a nickel hydroxide compound anode and an oxide absorbing alloy for the cathode) , manufacturers claim the batteries retain 70 to 85% of their capacity after one year when stored at 20 ºC (68 ºF). These cells are marketed as 'always ready', 'ready-to-use' or 'pre-charged' rechargeables. Aside from the longer shelf life, they are otherwise similar to normal NiMH batteries of equivalent capacity and can be charged in typical NiMH chargers. Low self-discharge NiMH batteries are good for photography and other high energy requirement applications. Due to the low self-discharge, they are also suitable for long-term intermittent or low-current uses; they might last up to a year between charges, much better than ordinary NiMH batteries. They can therefore also be used for electrical clocks, remote controls, etc. This new type of batteries is marketed with over a dozen different brand names, but only actually made by three companies: Sanyo, Gold Peak and Yuasa-Delta. Therefore most of the brands are rebranded OEMs. Store Batteries in a cool, dry and well ventilated place out of direct sunlight. The ambient temperature should be kept below 30 ºC for long-term storage, but refrigeration is not necessary or recommended. Alkaline batteries have the highest energy density. The negative on the Alkaline batteries and all other primary batteries is their relative high internal resistance, which inhibits current flow. High internal resistance has little affect when powering low-current devices such as a TV remote control or a kitchen clock. The problem arises with digital cameras and other power-hungry devices. Today's digital cameras are extremely high-drain devices. The batteries must power a color LCD, a motorized zoom lens, an autofocus system, the multi-megapixel imager and the associated processing hardware.