Biosphere Solar DIY solar panel

Prepare the panel parts and remove the protective foil

Build only the solar panel. Follow the Biosphere Solar DEV KIT How-To, DEV KIT by Biosphere Solar BV, (c) 2024 Biosphere Solar, CERN-OHL-S-2.0. Part numbers are shown in brackets.

Wear latex gloves. Handle the solar cells gently: they are very fragile. Remove the protective foil from both PMMA sheets [1A, 1B].

Credit: DEV KIT by Biosphere Solar BV, (c) 2024 Biosphere Solar, licensed CERN-OHL-S-2.0. Source files and How-To: wikifactory.com/@biosphere-solar/dev-kit. Adapted by TwinWorks: the 3D model was assembled from the published parts, and the cells, seals, bolts, nuts and cable are simple stand-ins.

Arrange the bottom edge strips

Arrange the three bottom edge strips [11A] and the single bottom edge strip [11B] in their panel positions, with the square nut cut-outs facing down.

Press the M3 nuts into the bottom strips

Press the twenty nuts (M3) into the square cut-outs in the bottom edge strips [11A x3, 11B x1], with the nuts facing down. If the cut-outs are tight, use a hammer to seat the nuts.

Lay the bottom sheet on the strips

Lay the bottom sheet [1A] on the bottom edge strips. Keep the engraved stick seal between these lines side facing up and align the holes.

Apply the bottom EPDM seal

Stick the EPDM seal [2] onto the bottom sheet [1A], between the engraved lines. Cut the ends at 45 degrees and overlap them slightly.

Position the MDF cell template

Place the MDF cell template [3] on the engraved lines of the bottom sheet. Align OUTPUT with the template cut-out.

Place the cell beds and branding piece

Place the eight cell beds [5] and the branding piece [14] into their openings in the template.

Solder, test and place the eight cells

Wear latex gloves and handle the eight half-cut solar cells gently. Cut the dogbones in half and solder them to the cells using solder wire.

Measure each cell: it must read 0.2 to 0.6 V, with polarity matching the template's + and - marks. Place the tested cells in the cell beds, following those polarity marks.

Connect and test the cell string

Solder together the overlapping middle dogbones between the eight solar cells. Add tabbing wire at the template markings. Measure the complete string: it should read approximately 4 V.

Prepare and solder the output cable

Cut the cable to 0.5 to 1 m and strip the conductors. Solder the blue conductor to + and the brown conductor to - at the cell-string output.

Place the cell holder sheet

Place the cell holder sheet [9] over the template with its countersinks facing up. Align its four corner holes with the template.

Fasten the cell holder with the corner screws

Fix the cell holder sheet [9] to the template using the four small corner screws. Use a PH1 screwdriver.

Position the cork spacers

Align the four cork spacers [4A x2, 4B x2] with the holes in the bottom sheet [1A]. Leave the output-edge gap open for the cable-through piece [10A].

Fit the cable-through piece and TPU insert

Put the TPU insert [10B] into the cable-through piece [10A]. Run the cable through the insert and position the cable-through piece in the gap between the cork spacers, with the text facing up.

Seal and fit the top sheet

Apply the EPDM seal [2] to the top sheet [1B] between the engraved lines. Cut the ends at 45 degrees and overlap them slightly, as for the bottom sheet.

Lay the top sheet seal-down, aligning the holes. Sandwich the cable between the two seals at the cable exit.

Lay on the top edge strips

Lay the four top edge strips [11C] on the top sheet. Keep the countersinks facing up and align all bolt holes.

Fasten the panel with the 20 M3x18 bolts

Fit the twenty bolts (M3x18) through the top edge strips into the captive M3 nuts. Use a 2.5 mm Allen key and work around the panel, starting from one edge or corner.

Note: power output may be lower than expected.

Thread the cable through the core

The dongle converts the panel output to 5 V USB power. Keep the panel out of sunlight and leave USB devices disconnected during assembly.

Pull the free end of the panel cable through the dongle core (15), leaving enough cable to reach the converter input without strain.

Based on the supplied dongle instructions from the Biosphere Solar DEV KIT How-To. DEV KIT by Biosphere Solar BV, © 2024 Biosphere Solar, CERN-OHL-S-2.0. Part numbers are shown in brackets.

Position the cable clamp

Place the cable clamp (17) over the cable at the entry to the core (15). Align the two screw holes and keep the cable insulation beneath the clamp.

Secure the cable clamp

Install the two small clamp screws through the cable clamp (17) into the core (15). Tighten them evenly until the cable is held securely, without crushing its insulation or damaging the plastic. Gently pull the cable to check that it does not slip.

Solder the cable to the converter input

With the panel out of sunlight, solder the cable to the input terminals of the step-up converter (18): connect the blue conductor to input + and the other conductor to input −. Keep the conductors separate and avoid solder bridges.

Keep the hot soldering tip away from skin, cable insulation and the core (15). Work with ventilation and let the joints cool before handling them.

The converter is not represented in the 3D model.

Secure the USB port

Position the USB port (19) at the output end of the core (15) and secure it with its two screws. Leave the outer electrical pins accessible for soldering. Do not use either cable-clamp screw or the output-cap screw for this mounting.

The USB port and its two mounting screws are not represented in the 3D model.

Connect the converter to the USB port

Prepare two 1.5 cm pieces of tabbing wire. With the panel out of sunlight, solder them between the converter (18) output and the two outer power pins of the USB port (19): output + to USB +5 V and output − to USB ground. Use the port's pin identification to establish polarity, not its apparent left or right side.

Keep the wires clear of the core (15), adjacent pins and each other. Let the joints cool, then inspect for solder bridges and loose strands. Leave USB devices disconnected.

Adjust the output to a steady 5 V

Keep USB devices disconnected. Place the panel in sunlight and measure DC voltage across the USB power contacts, with the positive probe on +5 V and the negative probe on ground. Avoid bridging adjacent contacts with the probes.

Adjust the converter (18) until the USB output is a steady 5 V with correct polarity. If the output is unstable, do not connect a USB device. Return the panel out of sunlight before closing the dongle around the core (15).

Slide on the tube and fit the output cap

Slide the tube (20) over the core (15), taking care not to pinch wires or disturb the solder joints. Fit the output cap (16) at the USB end and align its screw hole. Keep the USB opening clear.

The tube is not represented in the 3D model.

Secure the output cap

Install the last small screw to secure the output cap (16). Tighten it until the cap is held securely without damaging the plastic. Check that the cap and tube are seated, the cable remains clamped and the USB opening is unobstructed.