Portable solar panels produce about 5-6 amps of current in direct sunlight. Most portable panels’ sizes are around 100W. The "maximum current" is rated at 5.5-6A and the "maximum voltage" is rated at 17-18V. However, these "maximums" are perfect or laboratory conditions only. In practice, the amperage generated by a portable solar panel may vary by more than 50%.
The amount of current produced depends on factors such as sunlight exposure, angle of the sun, and panel cleanliness. Many RV owners or solar users use portable panels with charge controllers to charge batteries that then power multiple devices.
To better understand and choose the portable solar panels you want, you need to know the basics of solar panels. Here are some factors you must know, as well as selection criteria.
The basic measure of a solar panel’s performance is "watts". It is a unit of power and is the product of the voltage and amperage (current) produced by the panel.
Watt (power) = Volts (voltage) x Amps (current)
Current is the transfer of electric charge, or more precisely - electrons, from one point to another, which produces what we call electricity. The unit for measuring current is the ampere.
Voltage can be roughly described as the force of current flowing from one point to another. This force is caused by the difference in potential (the difference in charge levels) between the two points.
Amp hours (Battery capacity)
As you can see from the name, amp hours are the capacity of the battery. It is derived from the product of amperes and hours. It indicates how many amps can be delivered in a given hour of the day. You can understand this with an example.
A 100Ah battery means that 10 amps of current can last for 10 hours or 5 amps of current for 20 hours.
Not only do you know the approximate amperage and time based on the battery capacity, but you can also get an approximate charge time based on the power and amperage of the panel. For example, for the 100W panel mentioned earlier, assume it has a maximum current of 5.56 amps. When the panel is operating under ideal conditions, we can calculate the number of hours it will take to fully charge a 100Ah battery. Hours = 100 ÷ 5.56 = 17.98 h.
Pairing solar panels and batteries
Storing sunlight is not possible. However, batteries can store the energy produced by solar energy and be used when there is no direct sunlight, such as in the evening or at night. Pairing a solar panel with a battery is relatively simple, whether it's a lead-acid or lithium-ion battery.
You can make a simple connection directly - connect the positive terminal of the panel to the positive terminal of the battery and negative to negative. Generally, manufacturers do a good job of making the distinction between positive and negative terminals, such as color distinction.
Make sure you read the installation guide for solar panels before you start pairing them with your battery.
Although the solar panel can be connected directly to the battery, it is recommended to install a charge controller, sometimes called a maintainer, between the two. It can be very energy efficient and charge the battery in the best possible way. The charge controller also has the function of protecting the battery from overcharging and over-discharging.
How big of a battery does a 100-watt solar panel need?
As mentioned earlier, a 100W solar panel can produce about 5.56A of current. Depending on the intensity of direct sunlight received and the useful hours in a day, the panel will produce between 20 and 30 amp-hours (Ah) throughout the day. But that doesn't mean that a 30Ah and 12V battery is enough. Since the battery should not be fully discharged, doing so can damage the battery. Batteries can only be discharged to a maximum of 60% of their capacity, and for deep cycle batteries, up to 80%. Therefore, in our 100W panel case, a 50Ah, 12V battery is more appropriate.
Solar energy is a very flexible technology. The portable solar panel can power almost anything you can think of. Using multiple 100W panels can power your RV or mobile home. If you have enough panels, it can even provide you with pretty good accommodations.
Most top-of-the-line portable solar panels can even last more than 20 years, making it a great investment. It can also replace bulky and polluting diesel generators. In addition to improving your energy efficiency, this contributes its own energy to climate change mitigation.
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