The charging current is controlled by the current control circuit. General-purpose 3 terminal voltage regulator is used for control of voltage and current.
http://www.hobby-elec.org/e_car2.htm
An advanced battery charger design based on Maxim's battery charger IC MAX712. This device can fast-charge an NiCd/NiMH rechargeable battery.
http://wiredworld.tripod.com/tronics/batt_chg.html
a single LED indicates whether the battery charger s delivering a trickle charge or a fast charge, cricuit designed to charge 2-14 cells
http://www.edn.com/archives/1995/052595/11di1.htm
This circuit derives its power from a USB port and produces 5 and 3.3V supply rails for portable devices, such as digital cameras, MP3 players, and PDAs. The circuit allows the port to maintain communications while, for example, charging a lithium-ion bat
http://www.edn.com/article/CA185954.html
http://www.uoguelph.ca/~antoon/gadgets/solar1g.htm
This circuit is designed to peak charge Rx and Tx batteries. It's programmed for a C/2 charge rate for 250mAh and 500mAh batteries (charge currents of 125mA or 250mA). It'll charge Rx from 12V at the field, Tx from a 15V supply (like a car w/engine running). Use a 15-18V supply to charge at home (you should be able to find wall cubes with this rating). It is based on a Maxim IC, the MAX713.
http://www.uoguelph.ca/%7Eantoon/gadgets/peakchrg.htm
prevent overcharging and electrolyte loss by stopping charging when the cells warm up.
http://www.solorb.com/elect/tmpchrg/index.html
a shunt method is preferable than series regulation in solar-powered systems.
http://www.edn.com/archives/1997/112097/24di_05.htm