The Other Project - Solar Panels

In addition to the concrete counter tops we are also working on building our own solar panels from rejected solar cells. These rejected cells are available for about 20% of the cost of an unblemished solar cell. These cells were rejected because they either have very small chips or had some defect when they were being manufactured. We got 140 Watts worth of cells from eBay for around $120.

The soldering station that I setup on top of a table saw, and one completed series of cells

So we are in the process of building a panel for these cells to go on the top of the trailer. There was an old non-functional solar hot water collector laying around so that has been dismantled and a lot of the framing is being cannibalized to make the new panel frame out of. We cut down the frame to make some nice lightweight aluminum angle frame and the backing sheet metal will be the new backing on the panel as well as re-using the glass front panel.

The first step for the panels was to figure out the cell configuration. We are going with two series runs of 36 cells which will give about 20 V of output power each. These will be connected in parallel to provide around 7.6 Amps of charging current for the trailer battery.

The back of a set of cells... the three pads are where the next cell is connected

Each of the cells had to be soldered together. To fit the panel dimensions this means that creating 8 sets of 9 cells in series, 4 of which will be connected in each half of the panel. There are three solder pads on the back of each of the cells that need to be connected. This turns into a lot of soldering and the cells are very fragile. I managed to get all of the series connections, but just barely. All of the spare cells that we started out with were broken by the time I finished.

Putting flux onto the pads for the next cells to be connected

Soldering the cells into the string

The next step is to put together panel mounts for the cells and then get the frame put together. We are going to be using heavily primed and painted 1/4 inch plywood for the backing. The next step is working out the detailing for the panel edging. We'll post some of the work on that after we get it prototyped. More to come.

--Tom