solar powered home battery charging system

Extending the battery life is a good alternative to consume as little as possible and to contain the generation of waste which, in the case of batteries, is very harmful. With the energy of the sun and a little patience, you can create your own solar system to recharge the batteries. We explain how to shape it in just nine steps.


If you’ve taken a look at the image, you’ll already have an idea of ​​what you’ll need to build your battery charger, but we’ll break it down below:

  • Your preferred size copper charger board. If you choose large, you can expand the system in the future.
  • Battery holder. If they are not included in the bracket, you will need two bolts, one for the positive and one for the negative.
  • 100 ohm resistance.
  • LED with a voltage of 3.2-3.6 and a current of 1400 mA. It is a high intensity light that emits a diode and that you will need to install in the circuit.
  • Diode 1N5817 for the current to flow in one direction so that the battery does not discharge overnight.
  • 4 wires, one black and one red for the solar panel; one brown as a bridge and the other for welding tests.
  • Solar panel. The one you see in the picture has an output power of 3v at 150mA.

You may also need a multimeter to get useful information about panel voltage and current under different weather conditions. You will probably also need to use a soldering iron to make the battery charger, so if you have one and know how to use it, it will be a great fit for this project.


Step 1: Connect the cables to the solar panel.

For the wiring of panels, the most suitable formula will be welding, although other methods are also possible. If you plan to use the panel a lot or place several, it may be beneficial to mount it on a piece of wood or plastic. This way, it will be easier to maintain the wiring and avoid strain on the positives.

As you can see in the photos, duct tape was used to secure the cables. The red rectangles in the image indicate where the contacts are. Precisely there, you will have to fix the end of the cables, previously stripped.

Make sure everything is secure and the contacts are perfectly clean.

Step 2: Insert the battery and connect the circuit.

Place a fully charged 1.2V NiMH rechargeable battery in the battery holder. This battery will not be able to light up the LED by itself, so its voltage will be combined with that of the panel to put it into service.

Connect the positive red wire from the panel to the negative from the battery holder. Use an additional small wire to connect the positive of the socket to the longer end of the LED. This is the part that must always be connected to the positive of a circuit.

If the battery has been charged and the day is sunny, the LED should light up.

Step 3: Charge the battery.

The production of your own battery charger begins at this stage, for which it will be useful to review the scheme. As you can see the positive of the solar cell connects through the diode with the positive of the battery. If the panel voltage drops below 1.4 volts, there will be insufficient power to charge the battery. The reason the diode is used is precisely that current does not flow from the battery to the panel when there is a voltage drop.

Step 4: Charge the battery II.

The complete circuit is the one you see in this picture. For your understanding, the red lines marked at the bottom of the card show how the copper tracks align with the other side of the card. On the other hand, the lines marked in blue illustrate how the circuit is completed. Thus, the small silver strip at the end of the diode is positioned towards the positive terminal of the battery, thus allowing flow to but not from the battery.

Step 5: Charge the battery III.

In this image from the back of the board, you can see how the connections have been soldered and how they pass through the copper tracks. As you can see, the blue line corresponds to the diode, while the positive and negative of the battery should be placed as in the photo.

Step 6: Additional charger information.

Throughout this process, it is important to consider how many batteries you want to be able to charge at one time and how fast. With the charger mounted as before, the time you will need to charge your batteries will be approximately 13 hours. Therefore, it may be beneficial to add more panels to the system and thus improve its performance.

Step 7: What if I want more tension?

To double the voltage, you will simply need another panel in series. To do this, the negative of one panel must be connected to the positive of the other. This way you will reach 6v at 150mA, under maximum performance conditions. Remember that it will also be necessary to connect the batteries in series, that is, the negative with the positive.

Step 8: Add more current.

This way you will also be able to recharge your batteries at a higher speed. To multiply the current by two, you will need to connect the panels in parallel. So, connect the positive of one with the positive of the other and the negative with the negative. With this you will reach 3V at 300mA, instead of 150, although the voltage is maintained.

Step 9: Final ideas.

To make sure you don’t make a mistake when creating this system, it is important to use a multimeter. You should also be careful with the current entering the battery to avoid overcharging, damage and even explosion. With these precautions and if you have followed the steps outlined, you can begin to enjoy your own battery charging system.

Original project in Instructables.