Electronics > Power/Renewable Energy/EV's

nano-solar bench experiments.

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paulca:
Hi,

I'm looking to have a play with some mini solar panels on the bench, then work up from there to bigger panels.

The first project I want to try is a solar powered MCU.  The idea covers everything from MPPT to CCCV charging to boost/buck feedback loops.

The panels I have range from ones about the size of a watch face to 6 inch square.  From 100mW to alleged 3W.

The basic idea I had was to take a small STM32, an 18650, buck/boost convertor and write the MPPT control logic for the buck/boost feedback (injecting a pwm signal to the adjust voltage divider).  The MCU code is doing the boost/buck duty cycle regulation while moving the target output voltage to gain MPPT... or... run into "battery charge parameters" when they take over.

There is a lot of fun coding to do there.  With small micro panels the biggest risk is the 18650 battery. 

The thing I'm struggling with:

Picking a boost/buck circuit to start with.  I can pick from any number of chinese modules, but a lot of them seem to be aiming for much higher power and much lower efficiency than I will likely need to use small 1 watt solar panels.

On the other extreme I can order some tiny little SMD IC that will do it all internally.  Boring.  In the middle are buck/boost adjustable regulator ICs with impressive efficiency figures, but only supply 200mA up to 5V.  I believe it's something more like the later I need if I'm going to keep any power from the panel to charge the battery.

There are dozens of these chips, so trying to locate a dev board or module to play with is tricky.

Are there any "defacto" low power buck/boost ICs which are common enough to have dev boards on Ali/Ebay?

Any other suggestions?  I mean I could just use a mosfet, diode and coil, but I figured a bespoke buck/boost is likely to be inefficient?

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