Tracking Maximum Power Point For Solar Efficiency

In days of yore when solar panels weren’t dirt cheap, many people (and even large energy companies) used solar trackers to ensure their panels were always physically pointed at the sun to make sure they harvested every watt of energy possible. Since the price of panels has plummeted, though, it’s not economical to install complex machines to track the sun anymore. But all solar farms still track something else, called the Maximum Power Point (MPP), which ensures that even stationary panels are optimized for power production.

While small MPP trackers (MPPT) are available in solar charge controllers in the $200 range that are quite capable for small off-grid setups, [ASCAS] aka [TechBuilder] decided to roll out an open source version with a much lower price tag since most of the costs of these units are in R&D rather than in the actual components themselves. To that end, the methods that he uses for his MPPT are essentially the same as any commercial unit, known as synchronous buck conversion. This uses a specially configured switch-mode power supply (SMPS) in order to match the power output of the panels to the best power point for any given set of conditions extremely rapidly. It even works on many different battery configurations and chemistries, all configurable in software.

This build is incredibly extensive and goes deep into electrical theory and design choices. One design choice of note is the use of an ESP32 over an Arduino due to the higher resolution available when doing analog to digital conversion. There’s even a lengthy lecture on inductor core designs, and of course everything on this project is open source. We have also seen the ESP32 put to work with MPPT before, although in a slightly less refined but still intriguing way.

Thanks to [Sofia] for the tip!

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Boost Peak Power Tracking Battery Charger

[Rusdy] is building a solar charger for his electric bike, and quickly realized the lithium cells in his bike wouldn’t work well with the most common charge controllers out there. Solar cells have an IV curve, of course, and this changes with the amount of sunlight, requiring some conversion circuitry.┬áMost of the charge controllers out there operate in buck mode, but the commercial boost mode converters [Rusdy] needed for his 36V battery are pricey as all get out. What was [Rusdy] to do? Build his own Boost MPPT solar charger, of course.

The circuit used for the charge circuit is fairly similar to a boost converter, with a little bit of logic required to get the maximum power out of the solar cells. [Rusdy] had an Arduino lying around, so that took care of the logic, and by sampling the voltage and current with the analog pins, he can turn a MOSFET on and off to get the most out of his solar cells.

The finished product works perfectly with an efficiency greater than 87%. Charging current and the final trickle charge is adjustable through software, allowing [Rusdy] to get the most out of his solar panels and electric bike. The board itself is just a prototype and could use a layout revision, but we’ve got to hand it to him for cloning a >$300 charge controller with an Arduino and a few scraps in a part drawer.