DIY Solar Panel Kit 490W – 108 Mono Cells 6x6

The MR WATT 490W DIY solar panel kit contains 108 grade-A monocrystalline 6"x6" (156x156 mm) solar cells plus the accessories to connect them. It is the largest kit in our range: enough cells for three 12V panels or for a high-voltage string feeding a small off-grid system. We designed this kit in-house.

Three panels or one string: the design choices

• Three 36-cell panels in parallel: about 19 V and 8-8.5 A each, around 25 A in total on a 12V battery. With three or more panels in parallel it is good practice to fit a fuse on each panel: if one fails or is shaded, the other two can push more current into it than its cells and ribbons can handle.
• 108 cells in series: about 57 V at maximum power and about 8.5 A. This is the cleanest solution for a fixed system: thinner cables, no parallel connections, but you need an MPPT controller with a PV input of at least 100 V, preferably 150 V. At 25 °C the open-circuit voltage is about 67 V, and in sub-zero winter weather it exceeds 72-75 V.

K108ML3-AH technical specifications

How big the panels will be

Each 36-cell panel in 4 rows of 9 has a cell area of about 63x143 cm; three panels side by side take up about 1.9x1.4 m. Sizes assume 3 mm between cells, frame excluded. You need a 60-80 W soldering iron with a flat tip, a smooth heat-insulating surface and an encapsulation method (EVA, clear silicone resin such as QSIL 216, or double glass), not included. Guides and videos are in the Learning Zone on mrwatt.eu and on our YouTube channel MRWattDIY.

What you can do with it every day

In Southern Europe 490 W produce on average about 1.8 kWh per day over the year, around 2 kWh on summer days. With a suitable battery and a small inverter, in a country cottage or a frequently used cabin they cover an efficient fridge, LED lighting, TV, laptop, router and a water pump.

Frequently asked questions

What exactly is in the kit?

108 grade-A monocrystalline 156x156 mm solar cells, a few spare cells to make up for breakages during soldering or shipping, tab wire and bus wire, flux and a Schottky diode. The soldering iron, encapsulation materials, frames, junction boxes, fuses and charge controller are not included.

Which controller do I need for 490 W?

A controller is always required. On a 12V battery the charging current reaches about 36 A, so you need a 40 A MPPT; on a 24V battery a 20-30 A one is enough. With the 108-cell string the PV input must withstand at least 100 V.

Why are fuses needed with three panels in parallel?

If one panel short-circuits or is heavily shaded, the other two can dump their current into it, about 17 A, twice what its own cells produce. A fuse of about 15 A on each panel cuts the fault before it damages cells and ribbons.

Can I connect it to my home grid?

No. Self-built panels lack the certifications required for grid-connected systems: the kit is designed for off-grid systems with a battery and charge controller.

How long does it take to build?

With 108 large cells this is a multi-day project. Finish and test one 36-cell panel in the sun before moving on to the other two. The spare cells included cover the most common breakages.