MCP1640 5V step up from 4V solar cells

Posted on Feb 5, 2014

Solar/battery powered FSK transmiter regarding power supply section, including battery management. My main goal is to charge battery and supply power to the transmitter over day via solar cells and use battery over night and during low light periods. Since I have access to relatively cheap 4V 100mA (under lo

MCP1640 5V step up from 4V solar cells
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ad) solar cells, I intended to use following combination. Feed four solar cells in parallel to MCP1640 to step up voltage to 5V, use 5V to power MCP73833 battery charger, connected to p-channel mosfet according to application note AN1149, and at the end use MCP1700 for 3. 3V regulated power supply. Hand drawn schematic is provided in the picture. I`m pretty certain that this combination would work during sunny days, but as for the low light periods and day-night transitions I think this circuit is full of holes, since I really don`t know how MCP1640 would behave with solar cells in this situation. With diminishing light, voltage on solar cells would drop, current draw will further increase this drop to the point when MCP1640 shut it self down and the battery kicks in. Is it possible that with current load turned off, voltage on solar cell would jump to the point where MCP1640 would be able to start working and system would start oscillating Look I havn`t looked at your project this in depth, but its not that comon to wire us solar cells in parrallel. Perhaps this is the first area you should look at. A more common setup would be to have a solar array, with a high voltage - panels in series. These feed into the battery (normaly setupdown converter) and then a voltage regulator from this to your circuit. Yes, you are right about parallel wiring. Only way to wire them that way is to have perfectly matched solar cells, pretty...

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