Lightweight Solar Panel (12V Battery Charger)

My plan is to eventually install a considerable number of dismountable panels on a sailboat. For that, they have to be lightweight, efficient, relatively inexpensive, and relatively rugged. For efficiency, I chose monocrystalline wafers and an MPPT charge controller. These wafers are brittle with a relatively large minimum bending radius, so I needed a rigid yet lightweight support. I’m using a plastic honeycomb sandwich with polyester GRP skins. The finished panel with 35 wafers weighs 1.5kg, not including the controller. For redundancy in the face of wafer breakage, I chose a wiring scheme where groups of wafers are wired in parallel and then groups are connected in series. In the prototype, which I completed before finding a controller, there are 7 groups of 5 wafers. Each wafer gives about 0.6V, so that I have a total of about 4V. Failure of a single wafer will not break the series circuit, so that the panel should function with one or more wafers completely cracked. However, I could not find a commercial boost controller with a minimum voltage less than 5V. Chips exist from e.g. Texas Instruments to extract power from a single wafer (or N in parallel), but I chose to build a second prototype panel to connect in series with the first (giving 8V total) rather than design and build a custom controller.”

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