This is a charger for lithium ion batteries which takes its power from the USB port of a computer.It uses the MCP73861 or MCP73863 Li-ion battery charger chip manufactured by Microchip.The circuit is very simple to build based on the application note.source

This is a fast-charges 500-mAhr circuit for AA Ni-Cd cells. The number of cells can select by two switch, the circuit handles two to eight of AA Ni-Cd cells,The input voltage must be at least 15V. Charging starts when you plug in the battery.There is LED to indicate when the battery is fully , and the charger switches to trickle-charge mode.source

This charger is intended for charging small 12 Volt lead acid batteries, such as the gelled or AGM batteries of capacities between about 2 and 10 Ah, using a car’s electrical system as power source, regardless of whether the car engine is running or not.source

This circuit is intended for charging sealed lead-acid batteries with a solar panel in small and portable applications. The customary diode that prevents the battery from discharging through the solar panel has been replaced by a FET-comparator combination. The charger will stop charging once a pre-set voltage (temperature compensated) has been reached, and recommence charging when the voltage has dropped off sufficiently. The load is disconnected when the battery voltage drops below 11V and reconnected when it gets back to 12.5V.source

Here’s how to charge your lead-acid car battery with a solar panel.The simplest way: Get a voltmeter and a solar panel. Connect the panel to your battery and watch the voltage rise. When it gets near 14 volts your battery is charged. Disconnect your solar panel to keep it from overcharging your battery.Your battery can be damaged if you charge it too fast, so don’t get a panel that’s too big for your battery. Consult the battery manufacturer’s data to see how many amps it can handle, both while charging and discharging. If you happen to have a big panel and a little battery, there are tricks further along in this instructable.source