DIY Solar Panel Kit 200W – 72 Mono Cells 5x5

The MR WATT 200W DIY solar panel kit contains 72 grade-A monocrystalline 5"x5" (125x125 mm) solar cells plus the accessories to connect them. They are the same cells as in our 100 W kit, in double quantity: enough to build one 24V nominal panel or two 12V panels, depending on your system and the space you have. We designed this kit in-house.

One 24V panel or two 12V panels: how to choose

• 72 cells in series (24V panel): about 38 V at maximum power and about 5 A. The current stays low, so thinner cables and lower losses over long runs. It is the right choice for 24V batteries, or for 12V batteries with an MPPT controller that converts the extra voltage into charging current.
• Two 36-cell panels (12V each): about 19 V and 5 A per panel, around 10 A when wired in parallel. They can be laid on two different areas of the roof and also work with a simple PWM controller on a 12V battery.

To avoid: a 24V panel with a PWM controller on a 12V battery. PWM does not convert voltage and roughly half of the power would be lost.

K72M-125x125-A technical specifications

How big the panels will be

• One 24V panel, 6 rows of 12 cells: a cell area of about 77x153 cm.
• Two 12V panels, 4 rows of 9 cells: about 51x115 cm each, easy to fit between skylights and antennas.

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 200 W produce on average about 0.74 kWh per day over the year and almost 0.9 kWh on summer days. On a campervan travelling in summer, that means running the 12V compressor fridge, lights and pump and charging laptop and phones without plugging into shore power; on a boat, keeping the service battery charged even with the autopilot running for a few hours.

Frequently asked questions

What exactly is in the kit?

72 grade-A monocrystalline 125x125 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 and charge controller are not included.

I have a 12V battery: is a 24V panel worth it?

Yes, if you use an MPPT controller: at about 38 V and 5 A the cable current is half that of two panels in parallel, and the MPPT converts it into roughly 14-15 A of charge at 12V. With a PWM controller, build two 12V panels and wire them in parallel instead.

Which charge controller do I need?

A controller is always required, because connecting the panels straight to the battery overcharges it, with a risk of electrolysis and explosion. For 200 W on a 12V battery you need at least a 15-20 A controller; on a 24V battery a 10 A one is enough.

Can I use the included diode with two panels in parallel?

The Schottky diode is fitted in series with a panel's output to stop current flowing back at night or in shade. With two panels in parallel it is good practice to give each one its own blocking diode: the second must be bought separately.

Is it suitable if I have never soldered a cell?

Yes, the 125 mm cell is one of the most manageable formats. With 72 cells the job is longer: build a 9-cell string first, check its voltage with a multimeter, then carry on. The spare cells included are there precisely to cover your first breakages.