MPTT solar charger has reduced charging current

摘要

I built the Switchmode Solar Battery Charger described in Circuit Notebook,October 2018(siliconchip.com.au/Article/11274] to use with a 20W solar panel.I left out the sunset switch as I do not need it.I designed a PCB,made it using the laser toner method and assembled the board without any problems.It seems to work OK but adjusting VRl was a bit tricky.Initially,the wiper should be adjusted so that it provides a high resistance to the circuit.Otherwise,nothing happens when you connect it up,and you can't be sure of a wiring problem or not.An audible buzzing can be heard when the Mosfet is switching,and this can be used to confirm the unit is working and as an aid in adjusting the cut off voltage.The voltage at the panel is about 17.2V,as described in the article.