Folks, Hopefully this is the right place to ask this. I'm a software engineer with VERY limited EE experience and am trying to learn. At the moment, I've got a project that I'm trying to power using a 6v 6w solar panel, a load sharing solar battery charger, and a battery – though for this issue the battery is not in the loop. I'm also using a low drop out linear voltage regulator since based on the sun, voltages from the panel could vary.
When I plug the solar panel into the charger and take a voltmeter to the output leads, I get something nice and consistent around 5v (the panel is not in full sun at the moment). However as soon as I attach the voltage regulator (without any load) the voltage output from the charger goes pretty haywire jumping from 0 to 5. The output from the voltage regulator is around 1.8 or so. This definitely doesn't power my project since it needs 3.3v.
I'm using all purchased parts – didn't really design any circuit myself. The part list is above. Anybody know what is happening or how to get a consistent output? Thanks
Best Answer
The PV needs a minimum current to start the converter out in the sun, Indoors is like <1% of the current and insufficient to start it. It may need 5% of max to get started.
This has to do with the frequency range of the converter and the load impedance at a low frequency of the inductor. Once current source rises, it should be able to sustain the voltage until you apply a load that exceeds the supply. This is what a MPPT regulator will do match the load impedance between load and source to enable 80% of open circuit voltage. A simple LDO wont be able to capture the full power like a motor running a low RPM. You need a converter than runs at 80% full RPM or voltage in this case to convert to 4.2V.
Try measuring the following.
under a 300W lamp
then connect a large cap across PV , check voltage (1000uF)
then report results