DIY Bifacial Solar Panel Kit 190W – 36 Cells
36 bifacial monocrystalline 5BB solar cells, 156.75x156.75 mm (up to 5.4 Wp each on the front side) with 72 m of ribbon, a diode and a flux dispenser to build your own panel of about 190 W, 12V nominal, that also produces from the rear side.
A kit designed by MR WATT for glass-glass panels on pergolas, canopies, fences and balustrades, where light reaches both faces.
The MR WATT DIY bifacial solar panel kit contains 36 bifacial monocrystalline solar cells in M2 format, 156.75x156.75 mm, with 5 busbars on the front and solder pads on the rear, plus everything needed to connect them in series. With 36 cells you get a 12V nominal panel of about 190 W measured on the front side only: the rear adds energy whenever it receives reflected light. We designed this kit for people who want to build a transparent panel for places where a standard module would only cast shade.
When a home-built bifacial panel makes sense
A bifacial cell produces from the rear only if the rear sees light. The 5 to 20% gain stated by the cell manufacturer depends on three conditions:
- Transparent rear encapsulation: glass-glass, or glass on the front and a transparent backsheet. With an opaque white or black backsheet the cell works like a monofacial one.
- Free space behind the panel: pergolas, canopies, carports, fences and balustrades. A panel lying flat on a campervan roof or glued to a solid surface has its rear in the dark.
- A light-coloured surface below or behind: pale gravel, concrete, a white membrane or snow reflect far more light than grass.
If your panel will sit on a solid surface, choose one of our monofacial kits: they cost less and perform the same in that position.
Technical specifications K36BIFI-5BB-M2
| Number of cells | 36 |
| Technology | Monocrystalline silicon, bifacial cell |
| Cell format | 156.75x156.75 mm (M2), 200 µm thick |
| Busbars | 5 on the front (negative), silver solder pads on the rear (positive) |
| Power per cell (front, STC) | up to 5.40 Wp, efficiency up to 22.1% |
| Panel power (front, STC) | about 190 W, before lamination losses |
| Voltage at maximum power (36 in series) | about 20.7 V at 25 °C |
| Open-circuit voltage (36 in series) | about 24.4 V at 25 °C |
| Current at maximum power | about 9.4 A (short-circuit current about 9.9 A) |
| Rear-side gain | 5-20% with a suitable installation (cell manufacturer's figure) |
| Pmax temperature coefficient | -0.41 %/°C |
| Contents | 36 cells, 72 m of ribbon, 1 diode, 1 flux dispenser |
The panel's electrical values are calculated from the highest power class in the cell datasheet and refer to the front side only: always design on these figures and treat the rear contribution as a site-dependent margin.
How big your panel will be
- 4 rows of 9 cells: a cell area of about 64x144 cm, the classic 12V panel format.
- 6 rows of 6 cells: a square of about 96x96 cm, suited to one pergola bay.
Sizes assume 3 mm between cells, frame excluded. In a bifacial panel you can also widen the gaps: the light passing between cells makes the roof semi-transparent, at the cost of a larger panel for the same power. The 72 m of ribbon are enough to connect all 5 busbars of every cell, with margin for the string start and end connections. You need a temperature-controlled soldering iron with a flat tip, a smooth heat-insulating work surface and transparent encapsulation on both faces (double glass with EVA, or clear silicone resin such as QSIL 216), not included in the kit. 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
Counting the front side only, 190 W produce on a yearly average about 0.7-0.8 kWh per day in southern Europe and around 0.5 kWh in central Europe, with much more on summer days; on a pergola above a light floor the rear can add a few tens of watt-hours a day. With a charge controller and a 12V battery that means LED lighting for a pergola or gazebo all evening, an irrigation pump or a small 12V fridge for the garden, and power for cameras and an automatic gate on land with no grid connection.
Frequently asked questions
What exactly is in the kit?
36 bifacial monocrystalline solar cells of 156.75x156.75 mm, 72 m of ribbon for the connections, 1 diode and 1 flux dispenser. The soldering iron, glass and encapsulation materials, frame, junction box and charge controller are not included.
Does the panel produce more than a standard one?
Only if the rear receives light. With glass-glass encapsulation and the panel raised above a light surface, the cell manufacturer states a gain of 5 to 20%. Lying on a solid surface or closed by an opaque backsheet, it performs like a 190 W monofacial panel.
Which charge controller do I need?
A charge controller is always required: connecting the panel straight to the battery overcharges it, with the risk of electrolysis and explosion. With about 9.4 A at maximum power, and a little more when the rear is working, choose a PWM or MPPT controller rated at least 15 A, ideally 20 A.
Are bifacial cells soldered like standard ones?
Yes. The ribbon is soldered to the front busbars (negative) of one cell and brought to the rear pads (positive) of the next. Use the flux supplied in the kit and a temperature-controlled iron; at 200 µm these cells are sturdier to handle than the thin latest-generation cells.
Can I connect it to my home grid?
No. Home-built panels do not carry the certifications required for grid-connected systems: the kit is meant for off-grid systems with a battery and charge controller. If you need a finished, certified custom glass-glass bifacial module for a pergola, we can manufacture it for you.
