(a) How much do you want to spend?
(b) How far do you intend to be away from a conventional power source and where would you be needing the charger?
(c) what are your environmental concerns?
(a) Before anyone buys anything whether it is something they need or want, the first thing to consider is affordability. The need might be there but they may not have the money to purchase the item.
A solar phone charger is not very expensive. A fairly decent hybrid would cost around $ 100.00 but one can get a less expensive one for about $ 30.00. Some are just designed to charge your phone proactively while other can store their charge and can be used later to recharge the phone even when there is no sunlight.
(b) If you are always on the go or traveling to a remote location where you would be for hours, or even days or months without access to a conventional power source; that may determine what kind of solar charger to buy.
How often do you have enough sunlight where you are going? For how long would you be comfortable waiting for your phone to charge. Those are all things to consider before making decision on what kind of charger to purchase
The amount of time it would take to fully charge a cell phone would depend on the type of cell phone and the output capacity of the solar charger.
The following formula is used, as a rule of thumb, to calculate the specific amount of time to charge a cell phone:
(Amperes per hour of the cell phone battery / Amperes per hour of the solar charger) + 10%. Example: Suppose the cell phone battery is 5 Watts / hour and the solar charger has an output capacity of 2 Watts / hour.
Step 1: The unit of measurement has to be converted to current in Amperes, and the current in Amperes of both devices have to be divided (cell phone battery Amperes / solar charger Amperes) to come up with the time it would take to fully charge a particular device.
In this case we need to calculate the number of Amperes / hour for both the cell phone battery and the solar charger by doing the following (Watts / Volts = Amperes): Cell phone battery: 5 Watts / 12 Volts = 0.417 Amperes Solar charger: 2 Watts / 12 Volts = 0.167 Amperes
Step 2: To determine the number of hours it will take the solar charger to charge the cell phone, divide the Amperes per hour of the cell phone battery by the Amperes per hour of the solar phone charger and add 10%: 0.417 Amperes (call phone battery) / 0.167Amperes ( Solar phone charger ) = 2.50 hours
10% of 2.50 is 0.25, so the total number of hours that it will take to charge the cell phone is 2.75 (equivalent to 2.5 + 0.25). From this example, it can be concluded that it will take about three hours of direct sunlight to fully charge a 5 Watt / hour cell phone battery with a 2watt / hour solar charger.
(c) If you are someone who is very concerned about the environment and you want to use devices that are Eco friendly then you would have to decide which type of solar phone charger to buy. Solar chargers come in basically two different configurations. There is one that receives and converts energy from the sun and transfers it directly to your cell phone just like you would normally charge your phone in a conventional electric outlet in your home or office. There is another one that stores the charge in a battery as the solar cells collect and convert the heat from the sun. This type of charger can store the charge to be used when there is no sunlight.
The hybrid solar charger on the other hand can charge your cell phone in a conventional electric outlet and can also use the sun to charge your phone. Its advantage is that it stores charge for a very long time than a conventional solar phone charger , usually for more than a year. The downside is that some people would not consider it to be eco friendly (green enough) because of the electrical components that are incorporated in it.
Purchasing a solar charger is a good investment provided you have use for it. It comes in very handy when you are in a situation where you have to make that emergency phone call, and the only thing that would have made it impossible to make that call would be a dead cell phone in the middle of nowhere. There have been situations where people have been lost in jungles, barren lands, or find themselves in situations where they never expected, even being involved in an accident. Perhaps they intended to be out only for hours, hours turn into days, and days into weeks. The only means of communication with the would be through their cell phone. What if their cell phone battery is dead? Here comes a solar phone charger to the rescue.