Damaged battery charge/supply circuit with solar panel regulator



  • I attempted to use two zener diodes to regulate the voltage of a small solar panel into the usb port of my expansion board (ver 3). It appears as though I damaged the batter circuit as the board no longer will run on battery (and no LED). The ciruit I designed may have been defective - see attached. I'm interested in any feedback. The purpose of the circuit really was to prevent voltage feeding back through the solar panel with a 48 v. ze![alt text](![image url](solar_lopy_diode (1).jpg image url))ner diode preventing reverse current on the positive side of the panel (it didn't have a diode) and to limit the charging voltage with the with a 'bypass' zener diode (6.2 volt breakdown voltage) bridging the +/- side of the solar panel output. See attached diagram.solar_lopy_diode_mess (1).jpg



  • Your solar panel shunt zener limits the max panel voltage to 6v2. Forward drop across the 48v zener would be about 0.6v so max voltage across the USB from the panel should be about 6.2-0.6=5v6. USB is normally max 5V but you'd think you'd get away with the extra 0.6v . You sure you didn't get the zeners mixed up?


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