Reg: circuit to charge ultracapacitor from solar cell

Discussion in 'The Projects Forum' started by saranyaselvam, Mar 6, 2008.

  1. saranyaselvam

    Thread Starter New Member

    Feb 27, 2007
    Hi every1,

    I am designing a battery charger system which charges a 3.7 V Li-Ion battery from the solar cell stack (3.0 V).I use an ultra capacitor in between to store the energy whenever it is available from the solar cell.

    I face problem in connecting the solar cell stack to the ultra capacitor.

    can any1 suggest some circuit for this?....:confused:

    would a universal diode connected in between be helpful...

    I also face difficulty in getting digital voltage comparator circuits (which compares the voltage across the battery at every instant to that of its max voltage to produce control waveforms to the transistors in the circuit) because i always end up getting readymade IC's instead of the exact circuit.

    can someone suggest me any of the digital voltage comparision circuit...:confused:
  2. John Luciani

    Active Member

    Apr 3, 2007
    I would trickle charge the ultra-capacitor with a current sink circuit. Take a look
    at the National Semiconductor current source devices for some ideas.

    You can also build a simple current-sink circuit with an op-amp and a P channel

    (* jcl *)
  3. rwmoekoe

    Active Member

    Mar 1, 2007
    are you going to build a full functioning li-ion battery charger powered by solarcells?
    if so, the trickiest part will be the charger, not the solar cell power supply connection i guess.
    why don't you use a regular li-ion charger (find it at a hobby shop or r/c toys store), and provide the input supply voltage from solar cells.