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Using the BQ24002 from Texas Instruments it  is possible to build a simple and small charger  module for single lithium-ion (Li-ion) cells. The device is available in a SSOP20 package  and so does not require heroic assembly and  soldering skills. Individual cells are becoming available from  the main catalogue suppliers, but a much  cheaper option is to rescue cells from defunct  notebook  batteries.  In  most  cases  only  a  couple of cells are faulty and the others can still look forward to a long and useful life.  A single cell is ideal for any equipment that  needs a 3.3 V power supply, and will generally give a good operating life. The charger  circuit requires a 5 V input, which can readily  be obtained from a USB port or from any 5 V  power supply.   Circuit diagram: Single Lithium Cell Charger Circuit diagram   The  charge  process  begins  with  a  trickle  charge current. When the cell terminal volt-age is sufficiently high the charger switches  to a higher constant ...

4.2.4 Mercury Cell This cell is also m common use and consists of: an outer steel Container as the positive electrode, a cylinder of compressed zinc powder in the centre of the cell as the negative electrode potassium hydroxide as the electrolyte surrounding the zinc plate, and manganese dioxide and carbon as the depolarizing mixture. The cell is constructed so small that it is commonly used in watches, hearing aids, and miniature calculators. Its voltage is 1.35 V. Mercury cell The most important features of the mercury cell are: It can be stored for long periods without losing its charge through local action. It has a very high energy output for its size Its drawbacks are: It is toxic due to high mercury content It is expensive This cell has been replaced with a safer silver oxide cell.

Solar Cell Array Charger with Regulator circuit can be used to charge batteries from a solar cell array. The circuit consists of an oscillator, a DC-DC step-up or ‘boost’ converter and a regulator that pro-vides regulation of the output voltage.The oscillator is built around a hex Schmitt trigger inverter IC, the 40106B, one resistor, R1, inserted between the input and the output of one of the gates in the 40106 to supply charge to C3. Depending on the values of resistor R1 and capacitor C3 you’re using in the circuit, the oscillator will operate at different frequencies, but a frequency below 100 kHz is recommended.  By consequence, the oscillator frequency should not exceed the maximum ripple frequency of capacitor C2 connected on the output. C2 should be an electrolytic capacitor with a DC working voltage larger than the desired output voltage. Besides, it should have a low ESR (equivalent series resistance).  Solar Cell Array Charger with Regulator Circuit Diagram : IC1...