Most batteries can handle a voltage between 10.5 to 14.6 volts. If this limit is exceeded, it affects the battery’s lifespan and risks the battery burning.
It goes without saying that most solar panels’ output voltage is higher than that limit. AS a result, you will always need solar controllers to regulate the voltage from the panel. However, in some cases, the power produced by the panel is too high such that one solar controller is not enough.
Fortunately, it is possible to connect two or more solar controllers to regulate and maintain the battery more efficiently.
Connecting two or more solar controllers makes the wiring slightly technical, but don’t worry, we will discuss that. Let’s get started.
Can I use two solar charge controllers?
Solar controllers regulate the battery by sensing the resistance of the battery and sending in current depending on the resistance.
For instance, if the battery is on a low charge, it has a low resistance. As a result, the solar controllers will charge in bulk.
Similarly, when the battery is almost full, its resistance increases. Hence, the solar controller decreases its charging current.
In some cases, the power produced by the panels is relatively high such that one solar controller can’t regulate it efficiently.
Luckily, you can connect two or more charge controllers to manage the current efficiently.
Besides, you will need more solar controllers if you plan to purchase more panels, resulting in a voltage increase.
Additionally, you will need two or more charge controllers if you consider connecting the solar panels separately to maximize sunlight absorbed.
Can I connect two charge controllers to the same battery bank?
Connecting more than one charge controller is more advantageous to the battery than the solar panel because it regulates the power stored in the battery, which prevents the battery from undercharging or overcharging.
Since the batteries have been charging during the day, they have a higher voltage at night. Considering the law of physics, there is a higher possibility of this current flowing from the battery to the panels.
Fortunately, with the charge controllers, the current drainage from the battery will be stopped.
As we earlier said, you will need more than one charge controller in some cases. This gets us to our question, can you connect two charge controllers on the same battery bank?
One battery can seamlessly work with several charge controllers connected if luck would have it.
This concept is quite helpful, especially if you connect the solar panel in parallel, which implies each panel will have its charge controller resulting in a parallel connection of the charge controllers.
However, if the solar panels are connected in series, which forces you to connect the solar controllers in series, the news might not be too exciting because there is no change in the battery wiring process.
Can you wire charge controllers in parallel?
After making it clear that you can connect the two solar charge controllers on the same solar panel and same battery bank, it is good that we explain to you how to make the wiring.
You can wire a solar two charge controllers in two main ways, parallel and series.
A parallel connection means that the charge controllers will be connected in parallel, creating several discontinuous lines.
This way of wiring is quite helpful, especially if the solar panels are in parallel connection, which significantly increases the solar energy absorption in places because you can tilt the panels differently according to the sun’s position at a particular time.
Let us get our hands dirty.
How to wire two charge controllers in the same battery bank
Now, we will focus on how you can wire and use two solar charge controllers. If you are more of a visual person, this video will help you.
Step 1: Make an equipment ground connection junction stud
Charge controllers are first connected to a link distributor using the equipment ground on the sides. However, you will need to connect points on the link distributor when connecting two solar charge controllers, but it only contains one connection point.
Thus, we must be more creative on how to connect the two devices.
It would be best if you created a junction to combine the equipment’s grounds before they get to the link distributor.
Use screws and any fastening device to hold the junction device in the wire duct, as shown in the video.
Step 2: Connect the wire lugs to the junction
Usually, the wire lugs should connect the charge controller equipment ground to the link distributor.
But in this case, the wire lugs from the equipment ground should connect to the junction point. Do that for both charge controllers.
Step 3: Connect the junction stud to the negative bus bar
Afterward, connect the two wires from the equipment ground to the junction stud.
Add another wire lug to the junction stud and connect it to the center terminal of the negative bus bar located in the link distributor.
Step 4: Secure the charge controllers
Next, you need to have the charge controller secured tightly on the barker board using screws.
Step 5: Connect the negative battery wire to the link distributor
All the wires from the controller should be connected to the bus bar in the link distributor with respect to their terminal type.
The negative cable from the controller should be attached to the negative bus bar and secured using a wire lug. Note: You should do that for the two negative terminals from the two controllers.
Step 6: Connect the positive battery wire to the link distributor.
Typically the positive wire is marked with a red color. We will be doing almost the same thing we have done in step 5, with a different cable and on a positive terminal.
That is, connect the red cable to the positive terminal on the controller and its other end on the positive bus bar terminal secured with a wire lug.
Repeat the same process for the other device.
Step 7: Connect the solar array to the solar disconnect
Before you jump ring in connecting the arrays to the solar disconnect, ensure that you have installed the breakers for both arrays.
Connect the positive terminal of array number one to the positive terminal of the first solar disconnect.
Similarly, you should connect the negative terminal of the first solar array to the negative terminal of the second solar disconnect.
Repeat the process to connect the second solar array to the second solar disconnect.
Step 8: Wire the solar disconnects to the charge controllers
After wiring the solar arrays to the solar disconnects correctly, you can move on to connect the solar disconnect to the charge controller.
The positive and negative wires from the first solar disconnect connect to the first charge controller’s positive and negative pv terminals, respectively.
Do the same thing to connect the second solar disconnect to the second charge controller
Step 9: Reconnect the battery and the solar panel
Next, you should restore the connection between the link distributors
Additionally, connect the solar disconnects to the solar panel.
You should have a complete circuit with current flowing from the solar panels to the battery at the end of this process.
Step 10: Cover the wire duct
Lastly, place in the wire duct cover to shield the wires.
Eng. Matthew Joseph Nandirio is the Founder of walkingsolar.
After graduating from the University of Houston in 2002, matt started working as a Solar Electrical Engineer for several multi-national solar energy companies.
He has a wide range of experiences including solar system requirement analysis, planning, maintaining, debugging and even solar device development through research.
He now shares his 20 years of expertise through his articles on the walkingsolar website.
Further, he is also the author of two books on Solar Technology, “Solar Power for Villages” and “DIY Solar System for Dummies”.