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A 350 watt solar panel can generate up to 350 watts in perfect conditions. That is a given. But how many amps can this solar panel produce in different circumstances? The answer depends on several factors.
A 24V 350 watt solar panel can produce 8.8 amps an hour with an MPPT charge controller. This is the optimum performance result, but the weather, solar panel efficiency, location and other factors will affect the output.
How Many Amps Does a 350W Solar Panel Really Produce?
There are two ways to find out. The first is to divide the watts by the voltage. The other is to look up the panel specifications.
Let us look at the first option. Solar panels are either 12V or 24V. If it is 200 watts and higher, chances are it is 24 volts so let’s assume it is 24V:
350 / 24 = 14.5
On paper, a 24V 350 watt solar panel has an output of 14.5 amps.
But in reality, solar panels charge at a higher level than their nominal voltage. A 12V panel charges up to 18 volts, and a 24V can reach up to 38 or 40 volts.
To get a more exact figure, check the label specifications on your solar panel. Look for two things:
Maximum power voltage (VMPP): The VMPP is the highest voltage the solar panel reaches as it converts solar energy into current. In a 12V panel this will be at 18 volts, and in a 24V system around 36 to 40 volts.
Maximum power current (IMPP): The IMPP is the maximum power current or amps. This tells you the maximum amp output possible.
For example, you check the solar panel specification sheet and see something like this:
- Max power voltage: 38.5V
- Max power current: 8.84 amps
No need to calculate how many amps the solar panel produces as it is right there. But how many watts is required to produced this current output? Simple, multiply amps by volts.
38.5 x 8.84 = 340
To produce an 8.8 amp output, the solar panel must generate 340 watts, or close to its maximum rating.
How Amps, Watts and Volts Affect Solar Panel Output
The higher the voltage, the less current required from your power source. In other words, a solar panel charging at a high voltage produces more watts and requires less amps.
What you want is the solar panel to produce the highest voltage possible so amp requirement drops. The lower the amps, the less power the system will draw from the battery bank.
Lower amps is also ideal for homes, because overloading an electrical circuit is dangerous. For RVs and smaller systems, low amp draws means longer battery life.
Going back to the numbers again, keep in mind these are the optimum settings. If the VMMP is at 38.5V and IMMP is 8.8 amps, it means that is what the solar panel produces at its peak.
A 350 watt solar panel cannot produce 350 watts all day. Even if the sun is shining, the most you can expect is probably 330 or 340 watts on average.
So while a 24V solar panel can reach 38 to 40V, it can also drop depending on the weather. If it gets too hot for instance, the voltage will drop and increase the amp draw.
Contrary to what some believe, intense heat is not good for solar panels. In fact it has a detrimental effect. Suppose it is a hot day and the voltage drops to 34V.
As the voltage drops, so does the watt output. The amps drawn increases. The more amps are pulled, the faster your power load will drain the batteries.
One way to manage the voltage and amps is to use a charge controller. With the right controller you can get the best performance regardless of the weather.
Which Charge Controller Do I Need For 350W Solar Panels?
If you have a grid tied or MPPT charge controller, the system will run at the highest possible voltage possible. With a PWM controller, the voltage is limited to 14.4V.
A charge controller is a device used to keep solar batteries from overcharging. In a solar power system, the charge controller is connected to the panels and battery bank. The controller ensures the solar power going into the battery does not overload it.
There are two types of charge controllers, MPPT and PWM. An MPPT controller is an advanced system that automatically adjusts the output for the best possible performance.
With an MPPT controller, the system can use the highest voltage possible. As the day goes by and the variables change, the controller adjusts the settings accordingly.
With a PWM charge controller, the solar system is limited to 14.4 volts. If the voltage is higher than 14.4. the controller will drag it down, wasting watts in the process.
To illustrate the difference, let us go back to our previous example. You have a 350 watt solar panel. its VMMP (max power voltage) is 38.5 and the IMPP (max current/amps) is 8.8.
With an MPPT controller, you get these exact specs. With a PWM, the VMMP drops to 14.4 volts.
8.8 / 14.4 = 126.7
Instead of 340 or 350 watts, the solar panel only produces 126.7 watts, with 224 watts wasted.
As the voltage drops, the amount of current / amps needed to run appliances increases. A 300 watt appliance running on 38.5V draws only 7 amps, but the same appliance will draw 20 amps at 14.4 volts.
What Batteries Should I Use For a 350 Watt Solar Panel?
Depending on your set up, you may not need a battery at all. Or you may require several batteries to power your system.
If you are on a grid tied home, there is no need for batteries. A large solar array can power a house and run essential appliances. If the output is lacking you can switch to the grid.
Any extra solar power produced by the your system is sent to the grid. You can access these anytime, which should come in handy during winter when solar production drops.
If you are off grid, a battery bank is a must. Without a battery you won’t be able to store any excess power generated by the panel. You also need the battery to run loads during evenings.
Most solar systems use an AGM or lithium battery bank. AGM are SLA (sealed lead acid) batteries with a DOD (depth of discharge) from 50% to 70%.
AGM batteries are ideal because it is a compromise between lithium and cheap lead acid batteries. They do not need as much maintenance as lead acid, but do not cost as much as lithium.
If money is not an issue get a lithium battery bank. They offer the best performance, up to 100% discharge rate and zero maintenance. Lithium batteries in particular are great for large solar arrays that demand high performance.
The number of batteries required will depend on your system. A 50ah battery is enough for a 350 watt solar panel. But you will need more than one 350W module for an RV or even a solar powered mobile home.
What Inverter Do I Need For a 350 Watt Solar Panel?
The inverter size must be equal to the load you will run on the system. if you want to carry a full 350 watt load on the solar panel, the inverter must be at least 350 to 400 watts.
Inverters are rated according to their efficiency. A rating of 85% is the lowest you should get, and 90% or higher is better. The higher the rating, the less power is wasted during DC to AC power conversion. This also means less watts will be wasted when you load the system.
The larger your solar array is, the larger the inverter has to be. Because solar panels do not always produce maximum output, you can make the solar array larger than the inverter – up to 30% bigger – without causing any damage to the system.
If you are going to buy a 350 watt solar panel, determine first if it is enough. As you can see, the voltage, the charge controller type, batteries and weather all play parts. Doing the proper research makes it easier to find out if 350 watts is sufficient.
I am an advocate of solar power. Through portablesolarexpert.com I want to share with all of you what I have learned and cotinue to learn about renewable energy.