Using MCP73841 charge management controller chip, can be designed a very simple high efficiency charger electronic project for lithium ion or lithium polymer batteries .
This Li ion li polymer battery charger electronic project is very simple to design and require few electronic parts .
Due to the low efficiency of linear charging, the most important factors are thermal design and cost, which are a direct function of the input voltage, output current and thermal impedance between the external P-channel pass transistor and the ambient cooling air.
A standard value 110 mΩ, 1% resistor provides a typical fast charge current of 1000 mA and a maximum fast charge current of 1091 mA.
The current sense resistor, R1, is calculated by: R1=VFCS/IREG; where: IREG is the desired fast charge current .
A larger-value sense resistor will decrease the fast charge current and power dissipation in both the sense resistor and external pass transistor, but will increase charge cycle times.
The external P-channel MOSFET is determined by the gate-to-source threshold voltage, input voltage, output voltage and fast charge current.
Maximum power dissipation in this battery charger design occurs when charging at the 1C rate.
A status output provides information on the state-of charge. The current-limited, open-drain output can be used to illuminate an external LED. For powering this lithium ion , lithium polymer charger electronic project we must use a 5 volts DC regulated power supply .
For this Li battery charger circuit you can use Fairchild NDS8434 and International Rectifier IRF7404 MOSFETs transistors (both satisfy these requirements) or some other similar type .