Off grid solar: Introduction and Parts

Parts list

Solar panels – 8x Siemens SP75 75w 12v solar panels. I picked these up for free from someone on Craigslist who was cleaning out his garage. He used them for a few months around Y2K in case the world fell apart, then took them down and they sat in his garage since. Can’t beat free. I’ll be wiring these in a 4S2P configuration.

Batteries – 40 used LiFePO4 cells, supposedly CALB brand but I can’t identify them with any labels. The seller said they were used for a year by a STEM program at a local school. I will be capacity testing, shuffling cells around as needed, then wiring these up into a 24v system of 8S5P.

All-in-one charge controller and inverter – MPP Solar PIP-2424LV-MSD. This is a 2400w, 24v inverter with 80A Maximum Power Point Tracking (MPPT) charger. It is a “low voltage” model, supporting up to only 145v Voltage Open Circuit (Voc) DC from the panels. Many larger systems accept much higher voltage, but as this is an experiment with 12v panels in 4S, this will work just fine. One downside of this device is the high idle power consumption. Per the manual it uses about 50w at idle with nothing else plugged in. But for more efficient electronics, I would be looking at a few times the cost and I couldn’t justify that for this small setup.

Surge protection device – MidNite Solar MNSPD-300DC. This is an older version of their suppressor that supports both DC and AC systems. The newer versions are DC or AC – separate products. I will be wiring this attached to DC to protect the charge controller from surges from the panels in case of lightning.

Circuit breakers – 20 amp on the panel input. 125 amp on the batteries. I’m wiring in a box that also came with the solar panels.

Wire – 4 AWG pure copper welding wire for the batteries as the charge controller supports 4 AWG max. 12/2 AWG UF-B (Underground Feeder/Branch) wire for panels to charge controller. This wire can be buried or exposed to sunlight, which I will be doing for my temporary installation. Pure copper tinned lugs for battery connection.

I will show a wiring diagram in a later post.

Note that I am no expert on solar installation. This is my first attempt at taking what I have read online and seen on YouTube and setting up a small scale system. Comments and suggestions along the way are welcome! Stay tuned.

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