DIY USB or Solar powered Lithium ion or Lithium polymer battery charger
Lithium ion and Lithium Polymer batteries are very popular because of the very high energy storage capacity to weight ratio. Charging the batteries is very technically demanding as they must be precisely charged to 4.2 Volts other wise they can explode or catch fire. In this article I will show a circuit based on the CN3083 from consonance electrical company which you can easily build to make your own charger which will charge a single cell lithium ion battery. These are the batteries found on most mobile phones and also sold in shops. The CN3083 is a very good charging IC and is also far cheaper than most battery charger IC's. It is easily available on ebay.
The source for power for charging the battery could be a USB port or a solar panel. This IC is ideally suited for charging from a solar panel as it can automatically adjust it's current draw to prevent drawing too much current from the solar panel and causing too much voltage drop and charge interruption when there is low power from the solar panel.
Here is the schematic,
The IC is a SOP8, ie small outline package which is small but it is easily soldered if you have good soldering skills.
The circuits charging current is set to 1800 / R1 , which in our circuit comes to 1800/3.6 = 450 ma. A usb port supports a maximum of 500 ma so we are within spec with such values. It doesnt matter if your solar panel cant supply 450 ma, if so the CN3083 will automatically reduce the current so as to prevent overloading the solar panel.
Please note that although the attached datasheet is for CN3063, it is identical to CN3083's datasheet.
I will be adding the necessary schematic files shortly.
