You have a tray of SunPower C60 or Maxeon-style IBC cells on the bench. What happens between that tray and a panel that survives five years outdoors is a seven-step workflow, and most of the cost of getting it wrong lands in steps you have not thought about yet — handling, sorting, and encapsulation.
This page is the map. Each step links to the detailed guide for that step, so you can read the whole workflow first and then go deep only where your build actually needs it.
The Seven Steps Between a Tray of Cells and a Working Panel
Bare cells are a component, not a product. Everything that makes a finished panel reliable — the mechanical support, the moisture barrier, the electrical interconnect — is work you are taking on yourself when you buy cells instead of panels.
| Step | What it decides | Where it goes wrong |
|---|---|---|
| 1. Receive and inspect | Whether you got the grade and bin you paid for | Accepting a shipment before checking the bin against the datasheet |
| 2. Store | Whether cells survive until you use them | Humidity and stacking pressure between delivery and build day |
| 3. Test and sort | Final string current | Skipping it — one weak cell caps the whole series string |
| 4. Cut or buy pre-cut | Voltage, physical fit, breakage cost | Cutting in-house without the tooling or the yield to absorb losses |
| 5. String and solder | Long-term joint reliability | Thermal shock cracking cells; cold joints that pass day one and fail in month six |
| 6. Encapsulate | Service life outdoors | Wrong encapsulant for the environment — this is the top cause of early field failure |
| 7. Build for the application | Whether it survives its actual duty cycle | Designing for bench conditions instead of salt air, vibration, or weight limits |
Steps 1–2: Receiving and Storage
Check what arrived against the datasheet before the tray leaves the packing area. Grade and bin are the two things a listing can misrepresent without the cells looking any different, and they are the two things that set your finished panel's output.
Grade determines what you can build: A-grade cells go into anything you will sell, B-grade and cut cells have a narrower set of honest uses. The difference between them is covered in SunPower cell grades explained, and if you are still deciding what to order, the C60 listing buying guide covers what to verify before you pay.
Storage is the step people skip. Cells are stored in trays under controlled humidity for a reason — moisture on the busbars and pressure from over-stacked trays both cause damage you will not notice until the cells are already soldered into a string. The full handling procedure is in our cell storage and handling guide.
Step 3: Test and Sort Before You Commit
In a series string, the weakest cell sets the current for every cell in the string. This is the single highest-leverage step in the workflow, and it costs nothing but time.
Measure each cell before you solder anything, then group cells with similar output into the same string. Cells sold in the same bin are already grouped by the manufacturer, which is exactly why the bin on your packing list matters — it is the sorting work you are paying not to redo.
Testing procedure, meter setup, and how to read the numbers you get are covered in how to test and wire SunPower cells.
Step 4: Cut, or Buy Pre-Cut
Cutting cells changes voltage and current: a half cell produces roughly the same voltage as a full cell at roughly half the current. That is how you hit a target voltage in a small footprint, and it is why cut cells dominate IoT and small-format builds.
The trade-off is yield. In-house cutting without laser tooling produces breakage, and for small runs the scrap usually costs more than buying cells already cut to size. Standard sizes and the custom-cut path are covered in 125mm and 166mm cell sizes and custom cuts; if your format is not standard, our IBC custom cut service covers the tooling and minimums.
For sensor nodes and other small loads, size the cell count from the power budget rather than picking a size first — the method is in cut cells and IoT power budget sizing.
Step 5: Stringing and Soldering
IBC cells put both contacts on the back, which changes the soldering geometry compared with front-contact cells: interconnects run on the rear surface, and there is no front busbar to shade the cell. That is the efficiency advantage and the handling difficulty in the same design.
Two failure modes dominate. Thermal shock cracks cells when iron temperature is too high or dwell time too long — the crack often will not show until thermal cycling opens it. Cold joints pass a continuity check on the bench and fail months later in the field, which is the expensive version because the panel is already deployed.
Use tabbing wire sized for your cell format, keep iron temperature controlled, and reflow test every joint before encapsulating. Once a cell is laminated, a bad joint is not repairable — you scrap the panel.
Step 6: Encapsulation Decides Service Life
Encapsulation, not the cell, is what usually fails first in the field. A high-efficiency cell inside the wrong encapsulant is a panel with a short service life.
The three common paths are glass, ETFE, and PET. Glass is the most durable outdoors and the heaviest. ETFE is the standard choice when weight or flex matters. PET is the cheapest and yellows and delaminates fastest — it is why a low-priced flexible panel often stops performing within a couple of years.
What "flexible SunPower cells" actually means on a listing, and how encapsulation choice interacts with it, is covered in SunPower flexible solar cells: panel vs cell listings.
Step 7: Build for the Environment, Not the Bench
The last step is where identical cells produce very different results depending on the duty cycle you are designing for.
- Marine — salt air attacks joints and edge seals long before it affects the cell. Corrosion and vibration design is covered in SunPower cells for marine and boat builds.
- Drones and RC aircraft — every gram is a design constraint, which rules out glass and usually rules out rigid backing. See cells for drones and RC aircraft.
- Portable chargers — folding stress and connector choice matter more than peak wattage. Walkthrough in building a portable solar charger from SunPower cells.
- RV and off-grid — roof curvature and mounting method drive the encapsulation decision. See SunPower cells for RV and van builds.
When to Stop Building and Have It Built
Building from cells makes sense for prototypes, one-off formats, and learning what your product actually needs. It stops making sense at volume, and the crossover is earlier than most people expect.
The honest test: if you are producing units to sell, your scrap rate and labour hours per panel are now real costs, and lamination equipment is the line item that does not amortise at small volumes. At that point a factory-built panel to your spec is cheaper than the same panel built in-house — and it comes with process control you cannot reproduce on a bench.
We supply bare cells through our solar cells collection — 125mm cut cells and 166mm cut cells are the two standard formats — and we also build finished panels to spec through our partner factories when a project outgrows in-house assembly. Custom voltage, dimensions, and encapsulation are covered on our custom solar panels page.
Sampling runs from 5 pcs, with samples typically in 7–14 days. Send your cell format, target voltage, and annual volume and we will quote both paths — cells for in-house assembly, or the finished panel — so you can compare them against your own labour cost. Request a quote.
