Solar Charger Circuit (2nd Prototype)
Introduction: Solar Charger Circuit (2nd Prototype)
This time I'm trying to make some more practical solar charger circuits with multiple small size solar cells.
The capacity of the individual solar cell (Actually it's a small panel) is 5V 60mA.
A total of ten cells are interconnected together as parallel to support 5V output with a maximum 600mA current producing solar charger circuit.
This circuit will be a more practical solution than the previous prototype using only a single solar panel.
I'm interesting this circuit can support adequate capacity for fully charging 2900mAh 18650 battery within daylight hours.
Along with the charger circuit, I'm including additional circuit consuming generated electrical power during night hours with 1W LED.
As I mentioned in the previous solar circuit Instructable, this is an experimental circuit project to make a practical solar street lamp using high-power 12V Photovoltaic devices.
Step 1: Schematics
As shown in the schematics above, the solar power generating circuit itself is simple.
As I'm interested in the operational scheme of the solar cell, several measuring circuits are included such as a voltage meter, ampere meter, and battery capacity level meter.
I'll explain each measurement circuit one by one in the later step or at the other instructable as each device is a little bit complex.
The operational scheme of this solar circuit is simple like below.
- Solar cell produces about 50mA current when it receives sunlight (Although the solar cell specification claims a maximum of 400mA, the actual current I got under the sunlight through windows is 50mA)
- TP4056 lithium-ion battery charger circuit storing electric energy from the solar cell to 18650 battery (This module prevents overcharging and over-discharging of 18650 battery while operating)
- The 18650 battery storing energy from TP4056
- Battery level indicator circuit showing the capacity level of 18650 battery (This circuit was explained in other Instructables)
- 1Watt LED circuit is a load of this solar circuit and consumes energy stored in the 18650 battery
As this kind of solar circuit that charging battery is very common, maybe no further explanation will be necessary.
Step 2: Parts
The first design of this solar charger circuit was not much complex.
But I had tried to make this circuit more useful and more sub-components are added subsequently.
I'll explain the detailed circuit operation scheme in the later step (Step 5. operation scenario).
For making this circuit, the following components are utilized.
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- 5V 60mA solar panels (10EA, 68mm x 35mm size)
- 20L15T Schottky diode as blocking current from battery to panel
- Arduino Uno board
- TQ2-5V relay (2 contacts)
- 2N3904 NPN transistor
- 1N4001 silicon diode
- Resistors (1.2K, 330ohmx5, 10Kx2, 100K)
- LEDs (Greenx2, Yellowx2, Redx1)
- 1W white LED
- LDR (photo-resistor sensor)
- TP4056 Lithium-Ion battery charger
- 5V Boost-up voltage regulator (input 3V ~ 4.2V to 5V output)
- Push-button
- PCBs, metal supporters
- DuPont wires (male, female) and interconnection wires
- 18650 battery
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You can see each component in the schematics depicted in the steps later.
Step 3: Electricity Generating Capability of New Solar Panel
The most interesting part of this project is how much electricity can be produced by the newly made solar panel.
Therefore, I measured voltage as current on a very shiny day (1st April 2022) and the result is shown in the graphs above.
As my apartment is facing the western side, sunlight is bombarding the solar panel from 11:50 AM.
Again far less current is produced from the claimed solar panel capacity.
As 10EA of 5V 60mA panels are used, theoretically about 600mA should be produced.
But the actual is about 1/4 of current (160mA) is produced at its maximum.
Maybe as the panel is located inside balcony windows, the strength of sunlight seems a little bit degraded.
But the voltage measurement is quite OK as 3.8~5.2V is observed and most time more than 4.1V is produced by the new panel.
As the nominal voltage for the TP4056 charging battery is 4.1V, I can see the 18650 battery charging slowly but continually.
Therefore, the battery voltage increases from 3.6V to 4.1V while the solar panel gets sunlight.
As conclusion, new solar panel can support adequate energy producing capability for charging the 18650 battery. 267