Solar PV is very famous on phone charging application. Typical phone charging requires between 5W to 10W charging power. However, not all solar panels are made suitable for phone charging. Some may charge faster while some may charge slower with power limitation thus selection of solar panel is very important. Besides wattage rating, the voltage rating of the panel also determines the expected power generation. From the experiment in the video, same panel wattage but different voltage determines the power output quantity of a Solar Phone Charger.
For Solar DC direct application, the solar panel is directly connected to the DC load without the Maximum Power Point Tracking (MPPT) device in the system. The Solar Panel and the load will operate at their equilibrium voltage point which normally near to the nominal voltage of the load. The equilibrium point is where the intersection between the I-V characteristic graph of the solar panel and the operation voltage of the load. The operating voltage is then shifted away from its maximum point thus limiting the power production.
Solar Panel Foldable Charger
Solar Panel with foldable USB charger is a commercially available type of solar PV system which is specially designed compact for portability and convenience. Kindly check it out some good manufacturer at out affiliate link here !!!
As a comparison example, the sketch above shows the comparison of I-V curve between a 6Vmp and a 18Vmp solar panel. Both will operate at their maximum point if there is a MPPT device. However, here is not the case if solar panel is directly connected to the DC load. Both operating voltage will shift toward load operating voltage. If the solar panels are used in phone charging, the load operating voltage is somewhere about 4.2V which is the maximum allowable charging voltage for the Lithium Ion inside the phone or USB gadget. From the graph we can see both will be operating at same level of operating voltage but 6V solar panel has higher current.
6V Solar Panel
6V Solar Panel is best for powering USB application including 5V Phone charging. For a typical 10W application (2A 5V), it is recommend to use about 20Wp Solar Panel. Grab one of the solar panel at our affiliate link here !!!
Keweisi USB Meter
This is a very useful energy meter to record the necessary electrical parameter. It is not only useful for energy monitoring but it is also good tool for troubleshooting Solar Generation. Get one here at our affiliate link here !!!
Based on the I-V curve, the area under the graph is the power generation of the solar panel. Although both not operating at maximum power, but 18V solar panel has lower power generation due to I-V curve limitation. This will happen only if Solar Power cannot generate enough power to support the load.
Solar Panel will balance its output power to suit the load by tuning along the I-V curve. If the Solar Panel is large (for example 50W solar on a 5W load), the operating voltage will shift toward right side from the Maximum Point. This is why we need a DC converter to regulate voltage output to prevent the load from operating at high voltage and over powered. We do not have much concern about overpowered since the DC converter can take care of it. Less generation is happening most of the time especially during cloudy and low solar radiance level.
2 core Flexible Cable
Flexible cable is a synthetic rubber cable mostly used in portable tools such as hand drill or welding cable. It is made flexible and reasonably good resistant against outdoor and weather. Try surf and compare them at our affiliate link here !!!
5Vmp Solar VS 6Vmp Solar
In this case, you may think that 5Vmp Solar Panel should performs even better than 6Vmp. In my opinion, it maybe just in a grey area which this matter is arguable and may not be as much difference as you may think. A solar panel may need to overcome three possible voltage drops; 1) the temperature effect on Vmp value 2) the converter voltage drop and 3) Vmp dropped due to low light or cloudy condition.
If using 5Vmp Solar Panel, assume voltage drop only due to temperature effect, a hot sunny day the de-rated Vmp can be about 4.25 to 4.5 Vmp while a 6Vmp should be operating within 5.1 to 5.4 Vmp. If there is significant voltage drop in converter and low light condition, the 5Vmp may expect to be undervalued. Undervalued power dropped is very steep compared to having higher Vmp relative to operating voltage. Thus for overall assessment, I believe 6Vmp is still a better choice especially it is more superior in performance in cloudy or lower light condition.
Ferrule Lugs and Crimper Set
Ferrule lugs are used at terminals for tight and secure connection. Besides, it also prevent stranded cables accidentally touching adjacent power line that may cause short circuit. Grab 1 at our affiliate link here !!!
For a DIY Solar Phone charger, you need a Solar Panel, a DC-DC step down converter and the two core flexible cable of size about 0.5 to 1 mm square. As a rule of thumb to select the suitable capacity size of the solar panel, it should be at least 2 times the power requirement. If you are charging a 5W (5V x 1A) phone, a solar panel at least 6V 10-15Wp is highly recommended while charging a 10W (5V x 2A) requires a solar panel at least 6V 18-25Wp. Higher power rating ensure charging stability and higher speed especially during cloudy condition.
There are a lot of DC – DC step down converters or regulators in the market which allows you to convert from a regular solar panel to a regulated 5V power supply. DC -DC step down or buck converter need to be in USB converter module type. If you solder your own USB socket from a 2-wire DC-DC converter, it may not able to charge a certain phone especially apple phones. A USB converter module links the two data terminals as well to trick the phones to allow it for the charging. The cigarette lighter charger and solar USB charger are two of the best example.
Kindly take note on their supported input voltage range. Some USB charger might not support or not efficient in converting low voltage input such as 6V or lower. A good design is not only about correct selection of Solar Panel, but also the perfect match with its regulator to ensure conversion is efficient.
12V to 5V cigarette Lighter Charger
Cigarette Lighter Charger can be used as DC regulator for Solar DIY charger if the solar panel does not come with a DC regulator. Not all cigarette lighter may support as low as 6V input. Be sure to test it out or ask supplier. You can find them at out affiliate link here !!!
Solar USB Regulator
Solar USB Regulator is a DC – DC step down converter that used to convert regular solar panel and regulate into 5V output. It requires soldering to be made. Mostly can support wider range of voltage input from a Solar Panel. You can check it out at our affiliate link here !!!
My overall design Tips :
- Use 6Vmp Solar Panel rather than other voltage level. Do not get higher than 12Vmp Solar Panel which will have a large power cut.
- Use semi flexible solar panel type which is lightweight for easy portable. Second option would be standard aluminium frame solar panel. If possible avoid the PCB epoxy type Solar Panel as it may be easily damaged by outdoor weather.
- If possible avoid buying solar panel with built-in converter at the back. The converter is an electronic device and is not recommended to regularly heat up under hot sun. Furthermore, it may be hard to get replaced if the converter is faulty; better to have its own external converter.
- Get at least a 1 to 1.5 meter flexible cable so that the converter and the gadget can be placed under shade to prevent baking your phone or gadget under hot sun.
- Facing the solar panel directly to the sun when using. It will gain up to 20% more compared to panel facing other direction. Sun moves from East to West every 15 degree along the equator path. You may slightly moved your panel every couple of hours but I believe if under full sunlight your gadget should be charged fully under 2 hours.
- If you use other types of DC-DC converter especially cigarette Lighter USB Charger, be sure the charger support wide range of input voltage with high conversion efficiency even at low operating voltage.
Terminals Crimping Plier Set
This is a crimping tool with interchangeable jaw for crimping many types of terminals. It is a must have for DIY electronic and electrical for professional installation work. You may choose at out affiliate link here !!!
Before we end, we would like to give gratitude to you for taking the time to read the post. We would need readers like you to support us in order to keep growing. You can support us in the following ways :
Donate & Fund Raising
If you like my work, please send me a donation to encourage me to do more. Thanks
Aliexpress Affiliate
We are the member of Aliexpress affiliate marketing. Do support us by clicking the affiliate product links if you do wish to purchase them.
Like and Share
If you like our post, we need your support to like and share our posts or videos so that it can reach more and more people like you !!