A portable solar panel produces around 5-6 amps of current in direct sunlight. Most portable panels are sized at or around 100W, which comes with a ‘maximum current’ rating of 5.5-6A and a ‘maximum voltage’ rating of 17-18V. As the word ‘maximum’ suggests, these are output values at perfect or lab conditions.
Under real-world conditions, the amount of amps a portable solar panel produces may vary between 50-100% of the value mentioned above. The number of amps depends on factors such as exposure to sunlight, the angle of sunrays, and panel cleanliness. Portable solar panels are a great way to partly or fully power your appliances. Many RV/camper trailer owners or solar users use portable panels with a charge controller to charge batteries, which then power several devices.
Understanding Power Output of Portable Panels
Though the amps generated by solar panels is essential information, it is part of a larger equation. Understanding the basics of solar power output is essential to be able to set up a sound system. The following are some terms and their significance in choosing a portable solar panel:
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 amps (current) generation from the panel.
Watts (Power) = Volts (voltage) × Amps (current)
Every thousand watts is also known as a kilowatt (kW). Speaking of a 100W solar panel as an example, the following is how the volts and amps bring us to the value of a hundred watts:
100W = 18V × 5.56A
Current is the transfer of electric charge, more precisely – electrons, from one point to another, which results in what we call electricity. The unit for measuring current is amperes, often called colloquially as amps.
Voltage can be roughly described as the force with which current is flowing from one point to another. This force results from a difference in electric potential (difference in the level of charge) in two points.
Ampere-hours/amp hours (battery capacity):
As evident from the name, amp hours are the capacity of the battery, derived from the multiplication of amperes and hours. It indicates how many amperes can be delivered for the given hours a day. This is best understood with an example:
A 100Ah battery means 10 amps of current can be drawn from it for 10 hours or 5 amps for 20 hours.
10A × 10 hours = 100Ah
5A ×20 hours = 100Ah
This applies not just for energy drawn from the battery (discharging), but also energy supplied to charge the battery. Considering the 100W panel we discussed previously, it has a maximum current of 5.56 amps. Supposing the panel performs in ideal conditions (peak capacity), we can find out the number of hours required to charge the battery (100Ah) fully.
5.56A × x hours = 100 Ah
Hours = 100 ÷ 5.56 = 17.98
While watt is the unit for power, it only signifies electricity generated or consumed per hour, which makes it necessary to have another unit that also takes into consideration the time for which the power was consumed or generated. Thus, the multiplication of watt and hour gives us watt-hour (Wh). Every 1000 Wh is also known as a kilo-watthour (kWh). For example, the 100W panel in discussion generating peak power for 4 hours will give:
100W × 4h = 400Wh or 0.4kWh
Pairing a portable solar panel with a battery
Solar panels are helpful devices to harness free, clean, and omnipresent energy. However, nights and cloudy days make it difficult to fully rely on solar. There can be times when there is more sunlight throughout the day than you need for power generation, and sometimes there is less than you need.
It is impossible to store sunlight, but batteries make it possible to store the energy generated from solar and use it later when direct sunlight is not available, such as during evenings or nights. Pairing a portable solar panel to a battery is relatively simple, whether it is a lead-acid battery or a lithium-ion battery.
A direct pairing involves making two simple electrical connections – connecting the positive terminal of the panel to the positive terminal of the battery and similar for the negative terminals.
As discussed previously, solar panels come with a voltage rating of 17-18V. Batteries, on the other hand, are nearly always rated at 12V. Pairing an 18V panel to a 12V battery is ideal for making sure the current always flows from higher potential (solar panel) to lower (battery) and not the other way. However, panels compatible with 12V batteries are often known as 12V solar panels.
Before you start pairing your solar panels to your batteries, make sure you go through a good set up guide for portable solar panel systems.
While solar panels can be directly paired with batteries, installing a charge controller between the two is recommended. A charge controller helps charge the battery in a more energy efficient/optimum manner. Based on the amount of sunlight throughout the day, the voltage and the amount of amps a portable solar panel produces may be fluctuating and even zero at times. A charge controller ensures to smoothen these fluctuations while passing the power on to the battery.
Typically, a charge controller satisfies the following purposes:
- Control the rate at which current is drawn from the battery
- Prevent overcharging of the battery
- Prevent reverse current from battery to panel
- Divert excess current (shunt charge controller) to another load
- Monitor battery temperature
There are two main types of charge controllers – PWM (Pulse Width Modulator) and MPPT (Maximum Power Point Tracking). Without going into the technical details, MPPT charge controllers are more efficient and capable, since they can track the maximum power themselves to adjust the voltage and current level. They are slightly more expensive, but worth the expense and hence are becoming the common choice nowadays.
For more complex systems, a battery management system can be employed, which also performs the task of reporting the system’s status. Once installed, it can also help measure portable solar panel efficiency.
How Many Amps Does a 100 Watt Solar Panel Produce?
As mentioned before, a 100W solar panels generates about 5.56A current. Depending on the intensity and the hours of direct sunlight received through the day, the panel generates between 20- and 30-amp hours (Ah) throughout the day. But this does not mean a 30Ah and 12V battery should be sufficient. Why?
As batteries are not supposed to be discharged fully, doing so can damage the battery. Batteries can be discharged only up to 60% of their capacity, and up to 80% for a deep cycle battery. Hence, in our case of a 100W panel, a 50Ah, 12V battery is more suitable.
How Many Amps Does a 200 Watt Solar Panel Produce?
200W is now becoming a common size for portable panels, thanks to better efficiencies leading to decreasing panel sizes. A 200W panel, unlike a 100W panel, can have two different types of voltage outputs:
- 28V (suitable for 24V system)
- 18V (suitable for 12V system)
The following is the current generation from 200W panels:
- For 28V panels – 7 amps
- For 18V panels – 11 amps
Naturally, the values mentioned above and hence the amount of power produced depend on the factors discussed before. Considering we charge a 12V battery using a compatible 200W panel (18V), you can get up to 50-amp hours of daily solar generation, provided there is direct sunlight. Thus, a 60Ah deep cycle battery or a 75Ah regular battery should suffice in this case.
What Can a Portable Solar Panel Power?
Solar power is a tremendously flexible technology. It can be used to power anything from calculators and wristwatches to towns and cities. Portable solar panels can be used to power nearly anything. Using a bunch of 100W or 200W panels can power your RV or mobile homes, and even a proper residence if you have enough panels.
But the question is, what are portable panels best suited for? When it comes to solar panels, there is no ‘one-size-fits-all’.
The application of a panel mainly depends on the size and power rating it comes with. Portable panels are thus an excellent choice for camper trailers with a dual battery set up or simple off-grid camping set-ups, but not so much for home solar installations.
For an average system size of 6kW, you would require 60 panels of 100W capacity, compared to just 17 panels of 350W capacity. No doubt it would make your home more energy efficient, but at a higher cost.
This does not make much financial sense, as pairing many 12V solar panels increases the complexity of your system and increases your cost of solar panels significantly. Using the greater amount of wiring that comes with it is also against electrical engineering advice. Larger sized panels thus make a better choice for your home improvement upgrades.
However, portable panels make a perfect choice for city solar panel kits, such as off-grid kits for mobile cabins that can power a couple of led lights, a small fan, and a mobile device. Most people use portable panels to charge a 12V battery and then use it as their source of energy for a decided period.
Most top-rated portable solar panels even last for over 20 years, making them a great investment. Portable solar panels often replace the bulky and smoke-generating diesel generators. Along with improving your energy efficiency, this adds its tiny share to slowing down climate change.