This automatic NiCd charger for 9V NiCd batteries is using 555 timer properties and is very easy to build. Why is an automatic 9 volts NiCd battery charger? Because you can leave the battery for charging as much as you like: it will be always completely charged and ready for use when is needed. It wont be overcharged and it will not discharge.
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Button batteries or coin cell batteries charger circuit is simple to build, must be powered up from a 9V power supply circuit and can charge up to 5 button cell batteries.

D1 is a protection diode while R1 and C1 decouple the power live of the IC1 U2401B. D3 is for protecting the batteries in case we mount them wrong. R4 limits the current at 5 mA. After we connect the adapter to the main line, the button batteries will start to charge at maximum current for a period of time, after this it will start to charge in impulses. The impulse charging it is always made at 1/10 of the maximum charging current.
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This is a simple DIY iPhone charger circuit that can be built with a few resistors.
First, you need to buy 4 resistors with this values: 2 of 50 kΩ, 1 of 100 kΩ and 1 of 150 kΩ.
Ok, you got 4 resistors, now you need a 5V power supply, you guessed it, another USB cable. An USB cable has +5V on pin 1 and -5V (or ground) on pin 4.

If you can handle a cutter, gently cut off the isolation and reveal the wires inside. See what colors the wires have that are connected at pin 1 and 4. Note or remember and then with an soldering gun solder the cables to the iPhone charger circuit like in the schematic. continue reading…