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• Candle Power:  A single lit candle in conjunction with an inexpensive thermopile voltage generator provides enough power to charge a small battery when used with a small low voltage DC to DC converter.

• Solar Powered Lithium Ion Battery Charger     NEW
  The circuit below feeds a controlled current and voltage to a 3.6v lithium ion battery. The current is limited to 300ma and the voltage is limited to 4.2 volts. The circuit uses a LTC1734 IC from Linear Technology. No diode is needed between the circuit and a 6 volt solar panel....

• Two 12v Battery Isolator:  Linear Technology has just announced a neat little chip (LTC4412). It has been designed to be used in conjunction with an external P-channel power FET, to form an ideal diode function with a very low 0.05v voltage drop. The chip monitors the voltage on either side of the FET. As long as the voltage on the drain side is greater than the source side, the FET is turned on....

Muscle power drives battery-free electronics:  11/21/05  EDN Design Ideas  /  (added 10/06)  Your sweat and a super-cap replace the battery.

Nicad Battery Charger:  (schematic added 10/06)

Picref-5: Smbus Level-3 Battery Charger/Selector Reference Design Based on the PIC16C73a:  Microchip Application Note Published 11-May-98   (app note added 2/06)

Salt Water Battery:  (electronic circuit added 10/05)

Solar Cell Battery Charger:  (electronic circuit added 10/06)

Step Up supply charges battery while serving load :  The circuit in Fig 1 supports portable applications in which a microprocessor controls battery charging. Step-up switching regulator IC1 boosts VIN (5V) to supply a combination of charging and load current. (Note that the 5V source must have short-circuit protection.) IC2 is a high-side current-sense amplifier that monitors charging current. Commands from the processor are CHARGE ON /OFF and FAST/TRICKLE CHARGE  06/08/95  EDN-Design Ideas / (added 11/05)

The Amplified Zener:  A 13 volt Zener diode will work well for charging a 12 volt battery on Standby use. Or use a 14 volt zener a diode for a Standard 14.6 volt charge…. (circuit / schematic design added 10/06)

Zap Adapter:  "Don't throw away those seemingly un-chargeable, rechargeable batteries; they could very well be brought back to life with the aid of this simple circuit."  (circuit added 9/04)