How to build your own solar charger?
Since I plan on using my cell phone as a GPS tracker, I figured I will need much more battery time to keep it up for at least 12 hours. I also like the idea of renewable engergy very much and so I decided to build my own solar charger (the internet offers didn't seem too trustworthy on their specs).
We will build a charger having a nominal output of 5V and 500 mA. Exactly what comes out of a USB port.
We will build a charger having a nominal output of 5V and 500 mA. Exactly what comes out of a USB port.
STEP1:
The solar cells :)
I orderd mine from a swiss online store, that sells refurbished cells for quite good prices.
As you can see I got 4 cells, each providing 3 V and 250 mA.
The plan is to create a 2x2 configuration, doubling the voltage and current, and limitting it to 5 V afterwards.
I orderd mine from a swiss online store, that sells refurbished cells for quite good prices.
As you can see I got 4 cells, each providing 3 V and 250 mA.
The plan is to create a 2x2 configuration, doubling the voltage and current, and limitting it to 5 V afterwards.
STEP2:
Urgh, the back!
On the back of every cell, you have at least one + and one - ouput. In my case it is two each. As mentioned in STEP1, we need to connect two cells in a serial configuration increasing the voltage. The image above shows you how I connected the negative output of the left cell with the positive of the right cell.
The tape is just to keep the cells in place and isolate the other outputs for future handling.
On the back of every cell, you have at least one + and one - ouput. In my case it is two each. As mentioned in STEP1, we need to connect two cells in a serial configuration increasing the voltage. The image above shows you how I connected the negative output of the left cell with the positive of the right cell.
The tape is just to keep the cells in place and isolate the other outputs for future handling.
STEP3:
Argh, more back!
I agree and I am truely sorry, but this image is a mess. (but it's not difficult) :=)
Imagine your 2x1 cells from STEP2 as one big cell with one free + and one free - output. This step is to attach leads to all of those outputs. I simply rearanged the cells, so that the outputs are close to each other (use tape so they don't get in contact) and used more tape to keep the solar cells in place.
I agree and I am truely sorry, but this image is a mess. (but it's not difficult) :=)
Imagine your 2x1 cells from STEP2 as one big cell with one free + and one free - output. This step is to attach leads to all of those outputs. I simply rearanged the cells, so that the outputs are close to each other (use tape so they don't get in contact) and used more tape to keep the solar cells in place.
STEP4:
This is a mess too!
I have to agree (again). I have no idea why I tried to attach six leads to this small electronic device. The proper thing to do is to combine the leads you want, before connecting them any further.
What you see on the left side is a voltage regulator. It is powered with magic (at least in my mind), and will reduce voltages above 5 V to exactly 5 V by dissipating heat.
The device in its full glory is called a linear, positive voltage regulator and in this case, is a low-drop version (L4940V5) limited to 1.5 amperes. There are other "normal" versions, but since we are very close to the desired 5 V, compared to the nominal 6 V we are producing (at max), a low-drop regulator really is a must (and since we cannot exceed 500 mA in this configuration the current regulation is not of our concern anyway).
Viewed from above: connect the positive input to the left, both negative in and out to the middle, and the positive out to the right. This is important, because polarity does matter! There are negative regulators if you'd like to have it the other way around.
The USB-A connector to the right is fairly simple. Watching the (inside!) pins facing up, positive is to the very right, and negative to the very left (Look it up on the net if you're unsure). The middle ones are for data transfer which we don't need. If you want something else than USB-A, this is up to you.
I have to agree (again). I have no idea why I tried to attach six leads to this small electronic device. The proper thing to do is to combine the leads you want, before connecting them any further.
What you see on the left side is a voltage regulator. It is powered with magic (at least in my mind), and will reduce voltages above 5 V to exactly 5 V by dissipating heat.
The device in its full glory is called a linear, positive voltage regulator and in this case, is a low-drop version (L4940V5) limited to 1.5 amperes. There are other "normal" versions, but since we are very close to the desired 5 V, compared to the nominal 6 V we are producing (at max), a low-drop regulator really is a must (and since we cannot exceed 500 mA in this configuration the current regulation is not of our concern anyway).
Viewed from above: connect the positive input to the left, both negative in and out to the middle, and the positive out to the right. This is important, because polarity does matter! There are negative regulators if you'd like to have it the other way around.
The USB-A connector to the right is fairly simple. Watching the (inside!) pins facing up, positive is to the very right, and negative to the very left (Look it up on the net if you're unsure). The middle ones are for data transfer which we don't need. If you want something else than USB-A, this is up to you.
STEP5:
Yay :)
Everything is hooked up, taped down and actually working (you should check this with a volt meter before proceeding). I also isolated all the soldered pins to prevent shortening.
Everything is hooked up, taped down and actually working (you should check this with a volt meter before proceeding). I also isolated all the soldered pins to prevent shortening.
STEP6:
Cardboard please?
If you want to leave it just like this, that is entirely up to you. Since I wanted to make an outdoor friendly version, the first step was the ground...
If you want to leave it just like this, that is entirely up to you. Since I wanted to make an outdoor friendly version, the first step was the ground...
STEP7:
More tape!
...and a lot more adhesive, thik foil, to make it water resistant. This you should find in any well equipped stationary shop. Whilest making it rain proof, try not to completely cover the solar panels to maintain some efficiency.
...and a lot more adhesive, thik foil, to make it water resistant. This you should find in any well equipped stationary shop. Whilest making it rain proof, try not to completely cover the solar panels to maintain some efficiency.
STEP8:
CHAAAARGE!
Since we used a very good, low-drop voltage regulator and fairly good solar cells to start with, we may even charge our belongings in less light-happy conditions.
(Be aware that plastics generally age in UV-light. Try to keep your elctronic gadgeds out of direct sun light for too long. Hide them in the shade to keep them cool and fresh.)
Since we used a very good, low-drop voltage regulator and fairly good solar cells to start with, we may even charge our belongings in less light-happy conditions.
(Be aware that plastics generally age in UV-light. Try to keep your elctronic gadgeds out of direct sun light for too long. Hide them in the shade to keep them cool and fresh.)
Additional notes: if your device can handle more than 500 mA, go ahead and add further panels in a parallel manner. You need more voltage? Add more panels in a serial manner and also replace the voltage regulator with your specific needs. However, keep in mind that the USB port is only specified to 5V and 500 mA. I cannot be held responsible for any damage that might occur during production or usage of this and/or a similar device.
But if you have questions, feel free to ask and I migh even update this page. My mail adress is somewhere on my website. Have fun charging.
- Florian -
But if you have questions, feel free to ask and I migh even update this page. My mail adress is somewhere on my website. Have fun charging.
- Florian -