Shed Solar Panels

A local friend recently was doing some work upgrading some solar panels at a remote site he has, and offered me the older panels that weren’t optimized for his setup. I decided I’d pick them up and mount them on the shed to form a better, more permanent installation than I had previously, with a few random panels effectively just sitting in the yard.

They are slightly mismatched, but all 12V style panels, so close enough to work for my small needs. I replaced the cabling, and wired them all in series. With open circuit voltage on “12V” panels being ~21V, the six in series could generate about 126VDC. Fortunately I have a charge controller capable of handling that (TriStar MPPT-30). That feeds into a 100Ah lead acid deep cycle battery, and powers an inverter for some lights when required, and a small buck converter to run a Raspberry Pi out in the shed.

Overall the system is about 700W of total panels, by no means ideally placed or angled, so real generation is a fair bit less, but it’s enough for the very modest use I need in the shed, and it’s nice not to have to run an extension cord to run the lights for a few. I’d still like to add a bit more battery capacity, minimizing depth of discharge on lead acid batteries very much limits actual usage, but that can come later.

Mounting was accomplished with two ‘vertical’ rails of unistrut in the same direction as the ribs in the metal roofing, and then four horizontal unistrut rails to actually attach the panels to. A standard weather head from the hardware store brings the cables inside neatly.

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