Using solar energy to recharge batteries and power Arduino Uno

Overview

This tutorial aims to provide a step-by-step instruction to implement arduino protype projects that use solar energy via a solar panel and a rechargable battery. This tutorial is built on top of:

• Hannah Bonestroo’s previous tutorial on this website
• Alex Beale – 3 Ways to Solar Power an Arduino (Step by Step!)

Hannah Bonestroo’s tutorial provides a detailed description on how to choose the right solar panel with the right batteries. First, the solar panel should have at least 1.5 times the voltage of the battery. A 3.7V rechargable lithium ion battery should be charged by at least a 5.55V solar panel. Second, the capcatiy of the battery, determined by milliamps per hour (mAh) should be around ten times the working current (divide by an hour) of the solar panel for the best efficiency. For example, a battery with 3500 mAh should be powered by a solar panel with around 350 mA of working current.

Alex Beale’s tutorial uses a solar power manager that does not require soldering. This makes the process easier for users who do not have a soldering kit. The voltage of the solar power manager needs to match the solar panel being used. The solar power manager in this tutorial meets the need of a 6V-24V solar panel, has a 3.7V 14500 lithium battery holder, and a ph2.0 connector for other types of 3.7V batteries. In addition, a boost converter was built into the solar power manager to give a steady output of 5V to power aduino uno. If more voltage is required, an external boost converter is still required.

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Parts

1. 6V DC 583ma solar panel
2. Solar power management module for 6V-24V solar panel
   • This solar power manager includes a 3.7V 14500 lithium ion battery holder, ph2.0 connector, and a 5V boost converter
   • If your solar power manager has no battery holder nor boost converter, you have to buy these parts separately
3. 3.7V 6500 mAh lithuim polymer ion battery with ph2.0 connector (I got 5000 mAh because 6500 mAh was out of stock)
4. Arduino Uno
5. Jump wires

Note:

I got a 3.7V 106090 battery instead of a 14500 lithum ion battery, because the common capacity of a 14500 baterry does not exceed 3500 mAh. Since I have a solar panel with 583 mA working current, I would need a battery with around 6000 mAh capacity.

I got my solar panel first, so I had to accomandate the requirement of my solar penel. For recommandation, you can buy a 6V solar panel with 250 – 300 mA working current if you would like to use a common 3.7V rechargable battery.

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Wiring Diagram

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Steps

1. Solder the solar panel with wires like below (some solar panels have direct cable connections; in that case no soldering is needed). Solar panels should have user manuals on the correct places to solder. In this case, it’s the middle section.

2. Turn the solar power manager around. Make sure that the “6V” switch is at the “on” side and every thing else is at the “off” side (Please adjust the switch based on the voltage of your solar panel).

3. Connect the soldered solar panel wires to the solar power manager at the “solar in” section. Make sure the postive terminal on the panel is connected with the “+” terminal on the solar power manager (you might need a little screw driver shown in the picture to help you insert the wires!).

4. Connect the battery to the ph2.0 connector on the solar power manager. The positive and negative terminals should be matched up with the ones on the battery (I had to mannually switch the side of ph2.0 connector on the battery). If the battery is connected incorrectly, the “battery warning” light would be on.

5. Switch the “Battery Switch” to ON. If the battery is connected correctly and is being charged, the “Solar Charge”, “Battery Capacity”, and “Boot” lights are on.

6. When the battery is fully charged, the “Solar Done” light will be on.

7. Connect the solar panel manager with Aduino Uno. Aduino Uno should be powered up and run the code

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Videos

When it is working:

When the “Battery Switch” is at Off:

When the “Battery Switch” is at On: