Friday, September 25, 2009

                  I received many e-mail from people asking me how the capacitor charger work.
If you put, lets say 16V on a capacitor that needs to be charged then it would start to charge very fast and then slow down the closer it gets to 16V (look at a capacitors charging curve).The last 2 to 3 volts can take 75%  longer than the first 13 to 14 volts. To overcome this slow down effect we need a more constant current and it's done by increasing the voltage to +- 36VDC (rectified 24VAC). This DC voltage is used to charge the cap and the processor turns the charging mosfet off within 4uS when it reached it's set point (max 20V).
If the set point is lower than the capacitor volts, the processor will turns a mosfet on that connects a resistor bank to discharge the capacitor. EASY HUH?

The photos shows the LCD display with a 1 Farad Pro Ice capacitor that has been charged to 19.1VDC with a switching (processor controlled) rectified 24VAC.


  1. I am starting to collect components. What are the specs on the contactor?

  2. Hi Fritz, This is amazing. I would love to tackle this project. I'm not very skilled in electronics but I try to help myself. I did build a simple welder with CGC caps nothing fancy, I found the schematic on the net. Can you provide a parts list and also did you ever decided to source the PCBs? Does this involve any type of programming? I hope not because I've no clue of but willing to learn. Any help will be much appreciated.


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