# How To Connect 2 Solar Panels Together?

“Parallel Wiring” is the next method of connecting solar panels together that we’ll look at. The parallel connection is used to increase the overall system current and is the inverse of the series connection. Connect all of the positive terminals (positive to positive) and all of the negative terminals (negative to negative) on parallel connected solar panels until you have a single positive and negative connection to connect to your regulator and batteries.

When solar panels are connected in parallel, the overall voltage output remains the same as if they were connected in series, but the output current becomes the sum of each panel’s output, as indicated.

## How should two solar panels be connected?

One of the simplest methods to connect your solar power systems is to connect them in series. When two fixed solar panels of the same wattage are connected in this way, the system voltage is multiplied by two and the output current is maintained at the same level.

## Is it preferable to connect solar panels in a series or parallel configuration?

The most important thing to understand is that wiring in series raises voltage while wiring in parallel raises amperage. When constructing your system, both voltage and amperage must be taken into account, especially when looking for the ideal inverter for your needs.

A solar installation will almost always build a system that includes both series and parallel connections. This allows the system to run at a higher voltage and amperage without overheating the inverter, allowing your solar panels to perform optimally.

You may believe we’ve previously addressed this. However, there is one point to consider…

You’ll receive the most output if both panels are rated at the same maximum voltage. Our 115W SunPower solar blanket, for example, has the following specifications:

When you link two of these blankets in a row, you’ll get the following:

If you have two panels with different output ratings, the panel with the lowest maximum rated voltage determines the system’s maximum voltage.

Confused? Let’s have a peek at what occurs when our solar panel and solar blanket are connected.

Panel:

Blanket:

This is what you’ll get if you join them in parallel:

As a result, the solar blanket’s output will be reduced by 10% to (18.0 x 5.8 =) 104.4W.

It’s even better when you have a bank of panels connected in parallel, such as six on a motorhome’s roof. Then you begin to lose a lot of capacity.

If your battery management system can handle the maximum input power, you can link them in parallel.

How can you figure out what the maximum input power is? See the section above titled “Can two solar panels be connected to one battery?”

The maximum input power in our case is 304W. It’s fine because our REDARC Manager30 is rated for a maximum solar input of 520W.

The REDARC Manager15, on the other hand, is rated for 260W maximum solar input and would be too little for our needs. It would still work, but the extra capacity of the solar panel/blanket combo would be wasted.

• Determine which devices you want to use. Consider the following scenario:
• A refrigerator uses 7 amps and runs for 20% of the day (24 hours). So, in one hour, the average current draw is 7 x 0.2 = 1.4Ah.
• For 5% of the day, an inverter draws 45A. So, in one hour, the average current draw is 45 x 0.05 = 2.25Ah.
• For 20% of the day, USB ports and LED lights draw 5A. So 5 x 0.2 = 1.0Ah is the average current draw.
• For 5% of the day, the water pump draws 7.5A. 7.5 x 0.05 = 0.375Ah is the average current draw.
• When you add everything up, you get:
• 5.0Ah = (1.4 + 2.25 + 1.0 + 0.375).
• Let’s say it’s 6Ah.
• What exactly does this imply? So, in 24 hours, you’ll need 144Ah (24 x 6). 150Ah, please.
• Your solar panels should be able to provide this. Let’s see how big your solar panels are:
• Assume a maximum of 6 hours of sunlight.
• So they must give 150Ah to the battery in 6 hours, or 150/6 = 25A.
• At 25A, and assuming the solar panels supply 12V, you’ll require a solar panel capacity of 25 x 12 = 300W.
• Allow for at least 10% excess capacity:
• Solar panels of 300 x 1.1 = 330W are required.
• 350W is the most likely match for you.
• What kind of battery do you require?
• Deep cycle batteries don’t want to lose more than half of their capacity (Lithium batteries can go much lower without damage).
• In just 24 hours, you’ve used 150Ah. However, you cannot discharge less than 50%. So you’ll require 300Ah.
• In 24 hours, the solar panels provide 150Ah. Every day, they will fully recharge your battery (assuming 6 hours of usable sunlight).

In conclusion:

The solar panel and the battery are not simply matched. The loads on the battery must be known, the battery must be sized to fit the load, and the solar panels must be sized to fit both the load and the battery.

Yes! Never connect a solar panel to a battery directly. Between the panel and the battery, a regulator is required.

The regulator will be installed on the solar panel’s back or within a battery management system (BMS). The regulator controls (oddly enough!) the voltage from the solar panel and protects the battery from overcharging.

There are three different kinds. They are as follows:

## Is it faster to charge solar panels in series or parallel?

Solar Addict Supervstech explained that series charging is faster per day because low light conditions provide enough volts to start charging as soon as the light strikes the panels, rather than gradually increasing until the volts surpass the charging voltage.

## What happens when solar panels are connected in series?

Photovoltaic cells generate electricity at a voltage of 0.5 to 0.6 volts DC, with current proportional to the cell’s area and irradiance. The quantity of amperage supplied by a panel, or pv cell, is ultimately determined by the resistance of the connected load.

Amperage, or “amps,” is a unit of measurement for current, which is defined as the rate at which electrical charge flows past a fixed point within a circuit; the higher the charge, the higher the current.

Irradiance is the amount of solar radiation received at a given location on Earth; as the current demand from a cell increases, brighter sunlight (measured in watts per metre squared, W/m2) is required to produce the full output power; however, no matter how bright and intense the irradiance of the sunlight is, there is a maximum limit to the amount of current a solar cell can generate.

While individual solar cells can be connected within a single PV panel, solar photovoltaic panels can be joined in parallel strings to form an array of interconnected panels, boosting the total possible power output for a given solar application.

If a solar panel’s terminals are connected to nothing, the panel will generate no current because there is no electrical circuit for it to go through. When the terminals are shorted together, however, the current demand is quite high, and the photovoltaic panel generates its maximum output current, also known as the short-circuit current, ISC, from the available light.

When solar panels are connected in parallel, the overall voltage output remains the same as if they were connected in series, but the output current becomes the sum of each panel’s amperage. As a result of parallel wiring, the voltage remains constant while the amperage increases.

## Is a solar combiner box required?

The combiner box’s job is to combine the output of multiple solar strings. Each string conductor falls on a fuse terminal, and the output of the fused inputs is pooled into a single conductor that connects the box to the inverter, according to Daniel Sherwood, director of product management at SolarBOS. “This is a simple combiner box,” he explained, “but once you have one in your solar project, there are often additional capabilities built into the box.” Additional equipment includes disconnect switches, monitoring equipment, and remote rapid shutdown devices.

Solar combiner boxes also combine incoming power into a single main feed, which is then distributed to a solar inverter, according to Patrick Kane, Eaton’s product manager. Through wire reductions, labor and material expenses are reduced. “To improve inverter protection and dependability, solar combiner boxes are intended to provide overcurrent and overvoltage protection,” he stated.

“A combiner box isn’t necessary if a project only has two or three strings, such as a standard dwelling.” Rather, Sherwood explained, you’ll connect the string to an inverter directly. Combiner boxes are only necessary for larger projects, ranging from four to 4,000 strings. Combiner boxes, on the other hand, can be beneficial in projects of all sizes. Combiner boxes can bring a limited number of strings to a single area for convenient installation, disconnect, and maintenance in residential applications. Differently sized combiner boxes are frequently utilized in commercial applications to gather power from unusual building layouts. By dispersing the combined connections, combiner boxes allow site planners to maximize power while lowering material and labor costs for utility-scale projects.

Between the solar panels and the inverter should be the combiner box. It can reduce power loss when properly positioned in the array. “Price can also be influenced by location. According to Kane, location is critical since a combiner in a less-than-ideal site could significantly increase DC BOS expenses due to voltage and power losses. “It’s only a few pennies per watt,” Sherwood said, “but it’s vital to get right.”

Combiner boxes require very little maintenance. “The level of maintenance should be determined by the environment and frequency of use,” Kane added. “It’s a good idea to monitor them occasionally for leaks or weak connections,” Sherwood said, adding that if a combiner box is put properly, it should last the life of the solar project.

“Combiner boxes are not expensive compared to other equipment in a solar project,” Sherwood said, “but a bad combiner box might break in a dramatic way, involving shooting flames and smoke.” According to Sherwood, “everything should be third-party certified to conform to UL1741, the relevant standard for this type of equipment.” Make sure the combiner box you choose fulfills your project’s technical requirements.

The use of a whip, which is a length of wire with a solar connector on the end, is a new trend. “Rather than having a contractor drill holes in the combiner box and install fittings in the field,” Sherwood noted, “we attach whips at the factory that allow the installer to easily connect the output wires to the box using a mating solar connection.” “It’s as simple as turning on the toaster.”

Due to recent amendments in the National Electrical Code that mandate them in many solar applications, arc-fault protection and remote quick shutdown devices are more popular than ever this year.

The NEC revisions, as well as the goal for more energy efficiency and lower labor costs, are driving new technologies and components, according to Kane. Higher voltage components, complete mounting hardware, and bespoke grounding choices are among the new components.

## Is there a limit on how many solar panels I can attach to my inverter?

You’re presumably considering three different solar upgrade options:

2) Purchase a new, larger inverter, as well as additional panels.

3) Install a completely new solar system alongside the existing one.

Let’s go through each choice in depth so you can decide which is the best option for you.

The first thing to remember is that you can have a panel array with a peak power of up to 133 percent of your inverter’s rated peak power (which not many people are aware of).

Consider the following scenario:

You can also claim the solar rebate (STCs) on those extra panels if you don’t go above the 133 percent threshold. This will pay a large portion of their expenses (excluding installation costs and installer margin).

Adding panels is a cost-effective way to get more energy if your inverter is large enough. You might be wondering how this is possible if the inverter restricts the power output. As an example, consider a 3kW inverter.

Due to losses, 3kW of panels will typically provide just 80% (2.4kW) of their rated peak output.

After losses, 4kW of panels will produce 3.2kW of peak power. This can be safely clipped down to 3kW using a 3kW inverter. So you’re only wasting 0.2kW of electricity. On a summer day, that’s only for a couple of hours each side of midday. The peak power will be far less than the inverter’s rated 3kW in the mornings, evenings, and winter.

So, increasing the size of your inverter by 133 percent is an excellent approach to get more energy out of it.

There are two major cautions here:

2)It depends on your installer obtaining panels that are identical or extremely comparable to the ones you already have.

If you need more panels than your inverter can handle (using the 133 percent rule), or if you can’t find panels that are suitable, you have two options:

Removing a perfectly good inverter appears to be a waste of money and effort.

However, the sad reality is that many of the installed inverters have been cheap and unpleasant for the past seven years and are now on their final legs. If your inverter is a Sunny Roo, KLNE, JFY, JSI, Aerosharp, Sharp, or another brand that has a habit of going bang after a few years, now is a fantastic time to replace it with a real quality inverter like SMA.

Another reason to take the plunge and replace your old inverter with a larger one is that it’s much easier to add batteries and backup to one inverter than it is to two separate ones. So, if you want a battery-ready system with backup, a single, massive inverter is the way to go. (A battery ready system with backup varies from a battery ready system without backup, as explained in this post.)

If you do decide to upgrade your inverter, keep an eye out for the following pitfalls:

a) Because panel technology is rapidly evolving, you may have difficulty finding replacement panels that match your present array. In this instance, you’ll want an inverter with two or more inputs so you may add more panels without disrupting the existing array.

b) If possible, have the work done by the original company, as they will be responsible for the system warranty.

c) I propose getting a SUNSPEC/MODBUS inverter. This is a communication protocol that will allow future battery additions easier. This is standard on all SMA models now on the market in Australia. SMA is the safest pick here, in my opinion.

ABB inverters can also communicate with MODBUS using a \$500 interface unit. Although Fronius’ data sheets say that all of their inverters support MODBUS, word on the street is that it is only available in their more expensive ‘hybrid’ variants. Perhaps someone from Fronius has anything to say?

d) You can’t get a rebate for the inverter, but you can get a rebate for the solar panels. So put as many panels on that inverter as you can (133 percent of the inverter’s rated output), because the rebate (STCs) will pay a big portion of their cost.

If you don’t want to replace your current inverter, you have three choices:

If backup batteries aren’t a priority, this approach makes a lot of sense. You get a brand-new system with its own warranty. Installers are so proficient at installing entire systems that they don’t have to tinker with old solar wiring, thus it can frequently be less expensive than replacing your existing system. Yes, you can claim the solar rebate (STCs) on your second system; however, any stated rates will already include it.

As a result, to summarize:

It’s important to note that most inverters can be legally oversized by 133 percent. With your current inverter, you may be able to get all of the electricity you require.

If 133 percent of your inverter’s rating is insufficient, you can replace it to allow you to install more panels. Just keep in mind that while it is not as simple as a new installation, it might be quite costly. If you’re buying a new inverter, look for one that has MODBUS/SUNSPEC connectivity so you may add batteries later. And if the work is done by the original company, your warranty should be valid. However, you are wasting your old inverter.

It is frequently less expensive to install a completely new solar system, whether utilizing a traditional string inverter or micro inverters. These two systems will operate well together in grid connect mode, however adding batteries and backup will be more difficult afterwards.

And I’d be remiss if I didn’t mention that you may use my free service to get prices for a solar system upgrade.

## Is it better to have more solar panels with greater amps or volts?

Through a solar charge converter, both volts and amps are fed into the battery bank. If you utilize an MPPT controller, the greater voltage is decreased to the correct charge level, and the amps that come off the panels rise as the voltage drops.

## How can two solar panels connect to a 12 volt battery?

Simply connect the positive terminal of one solar panel or battery to the positive terminal of another solar panel or battery, and vice versa (respectively) as illustrated in the diagram below to wire two or more solar panels and batteries in parallel.

## What is the best way to piggyback a solar panel?

Instead, connect the Positive Lead (+) on your Solar Panel to the Negative (-) on your Solar Panel, and the Negative () Lead to the Positive (+) on your Second Solar Panel to create a ‘Series’ connection.

When two panels are connected in series, the voltage and wattage are multiplied by two. (When two panels of the same Voltage are used) The Amperage rating remains the same.