Homemade solar charger. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

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The summer season is coming, it's time for vacations and going out for outdoor recreation. So I, after several trips to nature and suffering with a gasoline generator, which is heavy, decently rumbles and stinks, I decided to get a solar charger. I need to charge my walkie-talkie, e-reader, laptop, LED flashlight, camera and mobile phones, use an LED lamp, and possibly recharge a 12 volt lead battery. On the Internet, chargers for charging the listed equipment exist, but at the same time they are very expensive, and they have a weak solar panel. As always, we, pensioners, are under the pressure of "toad" and we are not looking for easy ways.

I bring to your attention my design, collected on the basis of publications from the Internet and my improvements. My charger has a power of 20 watts and consists of two panels 12 V - 10 W 30x35 cm, in the unfolded position the solar panel is 35x60 cm. And it provides output stabilized voltages 14 V - 20 W, directly from the panels and from the built-in battery 14,8, 4,3 V - 5 Ah to power a laptop or tablet, as well as two USB outputs 4,3 V - 5 Ah each, for a total of 8,6 V - XNUMX Ah.

The panel is assembled in the form of a "diplomat", which, when closed, completely prevents damage to the panel itself. In fact, two independent chargers with built-in 7,4 V 4,3 ampere-hour batteries are made here. When connected in series, we get 14,8 volts at the output. 4,3 amp-hours, for our needs at night, or two 7,4v battery packs for a total of 8,6 amp-hours. There are also outputs for charging lead-acid batteries. I used lithium batteries from the outdated laptop batteries. As a rule, one section of the battery fails and the battery does not hold a charge. Selected only working banks. You can use any batteries, the circuit allows you to adjust the stabilized voltage at the output of the device. In my case, for charging 8,4 V lithium batteries, 14 V lead and USB devices and 5V mobile phones. With these voltages and using a current limiting resistor, you can charge all kinds of devices from 1,2V to 12-14V. You can use one 12V - 10W panel, then the diplomat will be half as thin and charge the battery longer.

Construction and layout

What we need is two solar panels 12 V-10 W, in my case these are Chinese-made panels worth $ 18, one piece, total 18x2 = $ 36. You can use other models in aluminum frames.

You also need a hinge to connect the panels into a "diplomat" you can use two suitable hinges from the lockers.

USB sockets in my case are additional sockets for the rear panel of the system unit, you can use USB sockets cut off from the USB extension cable, only they will have to be fixed in the panel with adhesive or clamps.

Batteries, two super-bright LEDs (can be from a flashlight) - are used to indicate the charge and at night to illuminate the tent if a powerful LED lamp is not used. Switches and other small things, everything can be seen in the attached photos.

Since a complete discharge of the batteries is not allowed, the design uses a battery discharge control unit that turns off the built-in battery when the voltage on lithium batteries drops to 6,1 V (you can easily reconfigure to any voltage for your batteries), the battery also turns off when the output is short-circuited .

The figure shows a complete diagram of one charger unit. I have my own block and my own batteries for each panel, you can simply parallel the panels and use one block, the dotted line on the diagram shows how to properly connect the second solar panel to one stabilization block.

(click to enlarge)

Since a complete discharge of the batteries is not allowed, the design uses a battery discharge control unit that turns off the built-in battery when the voltage on lithium batteries drops to 6,1 V (you can easily reconfigure to any voltage for your batteries), the battery also turns off when the output is short-circuited .

The figure shows a complete diagram of one charger unit. I have my own block and my own batteries for each panel, you can simply parallel the panels and use one block, the dotted line on the diagram shows how to properly connect the second solar panel to one stabilization block.

Description of the scheme

SZ1 - solar panel, diodes VD1 and VD2 protect the solar panel when charging from the mains adapter and from reverse polarity at the input. VD2 - protects the adjustable stabilizer DD1 from failure in the absence of voltage at the input of the stabilizer. Stabilizers DD1, DD2 allow you to get stable voltage for charging. Resistors R1, R2 set the necessary voltage to charge the batteries. Resistor R4 serves to limit the current when the battery is discharged, I have about 1-1 A with its nominal value of 1,25 Ohm. With resistor R5 we set the current through the indication and backlight LED VD4. The LED serves to indicate the connection of the built-in battery and indicate the presence of charge voltage. Dividers are assembled on resistors R6-R9, which set the necessary levels for USB.

The SA1 key switch allows you to select the mode of use, in the 14V position we can charge an external lead or other battery, while the SA1 / 2 contacts turn off the battery built into the panel. In the 8,4V position, the built-in battery is connected, it is supplied with voltage from the solar panel for charging, and it can also be used at night to charge any devices and power the LED lamp (I have a USB LED lamp for the computer).

In the economy mode, to illuminate the tent at night, it is enough for the glow of super-bright LEDs to be illuminated, while the total current consumption from the built-in battery will be 10 mA (5 mA LED and 5 mA KREN5V stabilizer). the output is a constant voltage of 1-20V at a load current of 16-1,5A.

Work with solar device

The device will turn on when the built-in battery is completely discharged (the battery protection unit disconnected the battery) only in the SA1 8,4V mode, while the SA1 / 2 contact group unlocks the battery, while it will be connected for charging automatically when the charge voltage is applied from the mains adapter or the solar panel is open. panels in sunlight, the illuminated LED will indicate the presence of charge voltage.

Switching on the operation with a charged battery, in the absence of sufficient lighting, is performed in the SA1 8,4V mode by briefly pressing the KN1 button, while the lit LED will indicate that the battery is connected. At the end of the charge of phones and other devices, by transferring SA1 to the 14V position, we turn off the built-in battery, the LED will turn off.

In the SA1-14V position and illuminating the solar panel with sunlight or connecting the AC adapter, the output connector for the external battery will have a stabilized voltage of 14V, which can also be used to charge the portable radio. In this case, the USB connector will have a voltage of 5 volts to charge USB devices, regardless of the built-in battery.

In the SA1-8,4V position and the solar panel is illuminated with sunlight or the AC adapter is connected, the output connector will have battery voltage and rise to 8,4 V during the charging of the built-in battery. At the same time, the USB connector will have a voltage of 5 volts. To light the tent, I use five-volt LED lamps designed for connection to USB, I connect them to the USB output, since the voltage of 5 volts is stabilized, and the lamp shines stably until the built-in rechargeable battery is completely discharged.

The battery control unit protects the built-in expensive battery from failure during a short circuit and from complete discharge, and also allows you to disconnect a fully charged battery from the circuit in standby storage mode. By replacing the zener diode VD1 and selecting the resistor R3, it can be adjusted to any cut-off voltage, for example, for a 12-volt lead battery, the minimum voltage should not be lower than 9-10 volts. A short press of the KN1 button allows you to connect the built-in battery in the 8,4 V mode, also in the 8,4 V mode, the battery is automatically connected when voltage is applied to the GN1 socket or the solar panel is opened to the sun.

Setup order

Block of stabilizers

To set up the stabilizer block, just in case, turn off the solar panel, apply voltage to the GN1 socket from the power source. We switch the switch SA1 to the 14V position and with the resistor R2 we set the voltage on 1 pin of the connector for an external battery of 14 volts, then with the built-in battery SA1 turned off, we switch to the position of 8,4V with the resistor R1 we set the voltage of 8,4 volts at 1 pin of the connector for the external battery (if we use another built-in battery, then set a different voltage). Be sure to start setting up with 14V mode! Then we connect a discharged built-in battery and by selecting a resistor R4 (made from a piece of a nichrome spiral from an electric stove), we set the maximum charge current to 1-1,25A. It should be taken into account that at the output for charging, the charge current from one solar panel will not exceed 500mA when two 1A panels are operated in parallel, when charging from a network adapter it will reach 1-1,25 A.

Battery control unit

Instead of a battery, we connect an adjustable power supply to the input of the block, set the voltage to 12-14 V, and connect an LED to the output through a 1k resistor. Briefly press the KH1 button, the LED should light up, then gradually reduce the voltage from the power supply until the LED goes out and measure the voltage at the input of the battery control unit, this voltage will correspond to the battery shutdown voltage. By selecting the resistor R3 of the battery pack, we set the protection operation voltage to 6,1v. By alternately increasing the voltage of the power supply and pressing the KN1 button, we start the battery and by reducing the voltage we take measurements several times, making sure that the protection settings are correct. Also, the closure of points A and B between themselves should lead to an immediate shutdown of the battery, regardless of the voltage at the battery input. By replacing the zener diode with a higher or lower voltage and selecting the resistor R3, you can rebuild the protection for any voltage.

Installation

The blocks are mounted on two separate fiberglass boards, the parts are located on the side of the printed wiring. Mounting tracks are made by cutting with a cutter from a hacksaw blade under a metal ruler. The dimensions of the boards allow you to use any parts. A drawing of the board of the battery control unit is shown in Figures No. 1 and No. 2, a drawing of the stabilizer board in Figures No. 4 and No. 5

Figure 1-3:

Battery control unit

Figure 4-5:

Stabilizer Board

Stabilizer ICs mounted directly on the aluminum frame of the solar panel through insulating spacers taken from a failed computer power supply. Boards and batteries are glued with double-sided adhesive tape and additionally glued along the contour with silicone hot glue. The indication LED is also glued with silicone hot glue. The field effect transistor of the battery pack is soldered directly to the board foil with a 60-watt soldering iron.

Internal view of the device

Details

Stabilizer DD1 can be replaced by any adjustable stabilizer for 3-5 A voltage up to 35 V, for example LM317, LM117.

The USB 5 V DD2 stabilizer is replaced by any 5-volt one for a current of 2-3A, for example, KR142EN5A or LM 7805.

Stabilizers

Diodes FR156 are replaceable by any silicon diodes designed for a current of at least 1,5A, for example, FR302, FR207, CT2A05, etc.

The KT361E transistor of the battery pack can be replaced with a similar one with any letter or with KT3107.

The field effect transistor of the battery pack can be replaced with any field effect transistor soldered from the old motherboard with an N type channel (N-Channel Enhancement Mode MOSFET), as a rule, the power and current of transistors in the motherboard in such cases is not lower than 10 A.

Field-effect transistor

The design of the "diplomat" latch is made of a piece of leaf spring from a hacksaw blade for wood or any other. The holes are punched with a puncher, since it is not easy to drill it without releasing the metal.

Diplomat latch

The connectors for connecting the AC adapter and an external battery can be any, but preferably with contacts isolated from the case, since I have two separate chargers and you can connect the panels in series using jumpers through these connectors and get a total voltage of 28 volts for charging 24 volt devices. If the common wire and one of the contacts are connected to the panel body, then it will be impossible to connect two panels in series. To isolate the common wire from the panel case, the DD2 chip is isolated through a gasket, if you do not plan to connect the built-in batteries in series or use one stabilizer unit for two solar panels, then the DD2 chip can not be isolated.

The reverse side of the panels is closed with plywood covers, plastic can also be used, the appearance of the "diplomat" will largely depend on the quality of the covers. The covers are screwed with M3 countersunk screws recessed into the plywood so that the screw head does not scratch the table. M3 threads are cut in the panel bodies for fastening the covers

For carrying, a nylon shoulder strap with carabiners from a student bag is used, and loops for carabiners are fixed on the body of the charger.

That's probably all. I think there is enough information for repetition or creative processing for my own conditions.

73! With respect to all!

Author: Milyushin Sergey Anatolyevich, ur3id@yandex.ru

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