Backpack with a solar panel charger

Portable module for a backpack (Pmpp~5 Wt)

Module specification:

dimension: 240x170x1.6 mm;

mass: 0,09 кг;

The module consists from 8 cells serially connected with dimensions: 100×30 mm.


There is a USB2.0-AF port to connect mobile devices to module studs.  In addition, there are some eyelets along the module’s edges to facilitate fixation and sun tuning.

Electrical data

Isc, A Voc, V Pmpp, W FF, % Impp, A Vmpp, V
1.01 5.74 4.45 76.52 0,92 4,81


Current/voltage diagram of 8-celled portable module.


Field tests of man-portable charge.

As a result of the tests it was identified that full charging of mobile devices demand a solar module with Q-point voltage value 7-8 Wt and current value ~1-1.5 А  (especially in low insolation environment of St. Petersburg, i.е. a module with power Pmpp=7-9 Wt. At such voltage charging a mobile device you have to use a 5W reductive power pulse stab, and for efficient use of power supply you should use a MPPT-controller.

Folding portable module (Pmpp~9 Wt)


Module specification:

General dimensions for unfolded module: 490×240 mm;

General dimensions for folded module: 185×240 mm;

mass: 0.28 kg;

quantity of assembly units in module: 2;

dimensions of a single unit: 170×230 mm;

One unit consists of 12 serially connected cells with dimensions: 102x20mm;

Shell material: waterproof Oxford 600D with polyurethane coating.

The result of the existence of two units of 12 serially connected cells in module is necessary charger output electrical characteristics. All the wires are hidden with waterproof fabric and lead-out wires are in a special pocket   There are two types of ports to connect devices and power pulse stab: USB2.0-AF port and input circular plug 5.5х2.1mm (female).


Current/voltage diagram of 12-celled units (1 and 2) and folding module (1+2).

Specification of used 12-celled units:

Unit Isc, A Voc, V Pmpp, W FF, % Impp, A Vmpp, V
1 0.73 8.53 4.75 76.29 0.68 7.02
2 0.69 8.47 4.52 76.84 0.64 7.03


Folding module specifications (2 units):

Isc, A Voc, V Pmpp, W FF, % Impp, A Vmpp, V
1.40 8.53 9.05 75.62 1.33 6.81


The module was tested with LSB set with radiation level close to 1,000 Wt/m2. The reductive power pulse stab was used to get 5W in output.

Stab specification:

-input voltage from 5W to 20W;

-output stabilized voltage — 5.4W;

-output max. current: 1.5А.

Output voltage is 5.4W, so it is 0.4W higher than USB standard. It was made to assure charger of mobile devices because as a rule they get charged with voltage higher than 5.2W only. 5.4W voltage is USB-friendly.


Power bank junction to solar charger with power stab.

Therefore, the tests of the folding module using reductive power pulse stab have showed that 9Wt solar module is enough to charger modern smartphones. However, there is still some design questions to solve connected to smartphone verification by solar charger (a stab with smart-ic function) and maximum power point tracking (MPPT-controller).

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