This cheap and easy to build NiCd/NiMH Battery Charger is suitable for automatically charging a wide range of batteries for many applications. Proper chargers are usually expensive and cheap chargers supplied with the original equipment often incorrectly charge the cells and dramatically shorten their life. This ‘intelligent’ charger was designed for high current and rapid charge applications such as cordless power tools and model racing cars.source

This article describes the construction of an AA battery powered 67 1/2 volt “battery”. This new rechargeable “B battery” is slightly smaller than the original Eveready 467 battery and is the same weight. The substitute battery can be made in different voltages and can be powered from a wide variety of sources.source

This is a solar charge controller, it’s function is to regulate the power flowing from a photovoltaic panel into a rechargeable battery. It features easy setup with one potentiometer for the float voltage adjustment, an equalize function for periodic overcharging, and automatic temperature compensation for better charging over a range of emperatures.source

This design is a 3A battery charger intended for use with 5-cell Ni-Cd or Ni-MH battery packs (but can be modified to suit other numbers of cells). The circuit includes automatic shutoff that occurs when the battery temperature rises 10°C above ambient.This battery charger was developed specifically for applications using either Nickel-Cadmium (Ni-Cd) or Nickel-Metal Hydride (Ni-MH) batteries that will accept a 3A fast-charge rate, and provides automatic shutoff of the high-current charge when the battery is full.The circuit use LM2576.source

This circuit can output 5V.The circuit can charge things like Ipods, PDAs, other devices that plugs into a USB to charge.The circuit very simple.All the parts can be easily purchased at your local electronic store, like Radio Shack.source