Solar charger for smartphone:
How a small solar panel can recharge a smartphone through the USB plug:
Recently, I had to spend 4 days, walking in kind of desert and I need my smartphone for record the track.
No power supply was possible during that time and I should find a way to recharge my phone during the walk.
I didn t want to carry heavy power bank or buy an unknown quality cheap solar power bank.
So, I spent some time to find a suitable solution. the main issue is that the solar panel I'm using is max 500mA and even with a regulator, cannot be coeected directly to the USB. A high current was requested at beginning and the voltage drop. Never work.
So, I develop a simple solution, light with a small old 650mAh battery:
- An IC (EUP 8054) connected to the solar panel charge the small battery
- A low consumption comparator, Max931, with hysteresis wait the battery to be >=4v
- When the battery is >=4v, the comparator enable (through an Tr inverter) a DC-DC switch LT1302 (Linear), providing 5v 600mA to the USB plug and to the smartphone
- When the small battery is empty, the Max931 switch off the DC-Dc and wait the sun to recharge again the 650mAh battery
- I add also a button to press when I want to force the recharge (forcing the comparator to commut)
It works well. I put it on the top of my back bag. Recharged several time my mobile during these 4 days, trecking in Gobi desert...
Laurent
No power supply was possible during that time and I should find a way to recharge my phone during the walk.
I didn t want to carry heavy power bank or buy an unknown quality cheap solar power bank.
So, I spent some time to find a suitable solution. the main issue is that the solar panel I'm using is max 500mA and even with a regulator, cannot be coeected directly to the USB. A high current was requested at beginning and the voltage drop. Never work.
So, I develop a simple solution, light with a small old 650mAh battery:
- An IC (EUP 8054) connected to the solar panel charge the small battery
- A low consumption comparator, Max931, with hysteresis wait the battery to be >=4v
- When the battery is >=4v, the comparator enable (through an Tr inverter) a DC-DC switch LT1302 (Linear), providing 5v 600mA to the USB plug and to the smartphone
- When the small battery is empty, the Max931 switch off the DC-Dc and wait the sun to recharge again the 650mAh battery
- I add also a button to press when I want to force the recharge (forcing the comparator to commut)
It works well. I put it on the top of my back bag. Recharged several time my mobile during these 4 days, trecking in Gobi desert...
Laurent
Discussie (1 opmerking(en))
bruno4water 8 jaar geleden
Congrats Laurent but one could just buy it with a 4,6 larger 3000 mAh Li-Po accu at a lower cost than total of all the parts, PCB and case. By the way, it's not because it is cheaper that the quality would be less than a home built one. Trust me, I know what I am talking about.
Here is the link for Conrad and I'm sure there must be other suppliers.
http://www.conrad.be/ce/nl/product/1362996?WT.mc_id=Mail:woensdag:20160810:Solarlader1362996&insert=NB&utm_medium=email&utm_source=woensdag&utm_campaign=20160810&utm_term=Solarlader1362996&m_id=4027895
Bruno
Here is the link for Conrad and I'm sure there must be other suppliers.
http://www.conrad.be/ce/nl/product/1362996?WT.mc_id=Mail:woensdag:20160810:Solarlader1362996&insert=NB&utm_medium=email&utm_source=woensdag&utm_campaign=20160810&utm_term=Solarlader1362996&m_id=4027895
Bruno
Antwoord
gfaman 8 jaar geleden
Hi Bruno,
thanks for your comments. I looked the product you mention. My proposal here is little bit different. I'm using a small battery (400mAh or 600mAh) for fsat charge and increase the number of charging cycle to the smartphone. With less sunshine, it will take hours to recharge a 3000mAh. This has also a weight benefit.
Surely, it must be possible to find cheap and quality but most of time, miracle didn t exist in this industry. I bought several solar charger and most of time, never work well. I did a reverse schematic on one of them and obviously, it cannot work. Charging with only one diode and basic Dc-Dc after to the USB, never work.
Now, what is priceless, it is the pleasure to build and use something by ourselves. Maybe the cost is not the first advantage but the satisfaction is it.
Laurent
thanks for your comments. I looked the product you mention. My proposal here is little bit different. I'm using a small battery (400mAh or 600mAh) for fsat charge and increase the number of charging cycle to the smartphone. With less sunshine, it will take hours to recharge a 3000mAh. This has also a weight benefit.
Surely, it must be possible to find cheap and quality but most of time, miracle didn t exist in this industry. I bought several solar charger and most of time, never work well. I did a reverse schematic on one of them and obviously, it cannot work. Charging with only one diode and basic Dc-Dc after to the USB, never work.
Now, what is priceless, it is the pleasure to build and use something by ourselves. Maybe the cost is not the first advantage but the satisfaction is it.
Laurent
Antwoord
Toon meer
1 Opmerking(en)
Updates van de auteur
gfaman 8 jaar geleden
- Remove the dedicated IC for lithium charger and using simple 2n2222 to charge with the full current from the solar panel.
- The second 2N2222 disable the charge when the battery is above around 4.1V (commutation level of the Max931). This function is necessary only in case there is nothing connected to the USB output. In case a phone is connected, the battery will surely stop to charge.
- The Max931 is still here to detect the small battery full and enable the DCDC to work
- Use of a special DC-DC, 5V-400mA output, LTC3525. Why special ? The output is disable when shutdown. Most of standard DC-Dc will have the inductance always connected. So, the current can always go through the inductance to the output. This IC open the inductance, so, no leakage current.
- The principle still the same:
* The solar cell will charge the small battery until 4.1V
* When 4.1V is achieve, the MAx931 will stop the charge and enable the DCDC. The small battery will charge the smartphone
* When the battery level go below 3.5V, the DCDc is shutdown and the charge restart
* the hysteresis of the Max931 is 0.6V
- The small battery (lithium) must have low impedance or the hysteresis of the Max931 will not be enough.
Simple and working well...
Laurent
gfaman 8 jaar geleden
PPihkala 8 jaar geleden
gfaman 8 jaar geleden
It was not mention but the solar panel must be 5V, up to 800mA (current max of the 8054).
I have tested this IC with many different 5V solar panel, from 100mA (0.5W) to 800mA (4W) and always ok.
I agree that a Max tracking point could improve the efficiency (I have one idea under development) but the idea here was to make something easy to make, working well.