Connecting two solar panels to one battery with one charge controller is easy. This article will explain how you do it, including schematics.
First of all, you should know this:
You cannot connect your solar panels directly to a battery.
When you connect your solar panels directly to your battery, you will damage the battery (lead-acid or lithium). You need a device that measures the state of charge of your battery and charges it accordingly, just like a car battery charger.
The device we are going to use is called a charge controller. As the word says, it will control the charging of your battery.
Purpose of a charge controller:
- Stop charging when the battery is full
- Adjust the charging voltage and current
use my MPPT Charge Controller Calculator to figure out what charge controller you need.
Step 1: Connect Your Battery to the Charge Controller
When you want to connect two solar panels to one battery, you must first connect your battery to the charge controller. It is crucial that you do this step first. If you connect the solar panels to the charge controller, you might risk destroying the charge controller in the process.
Wire thickness depends on your charge controller’s current to the batteries. For example, the Renogy Rover 20A delivers 20 amps to the battery. You need wires that can carry at least 20Amps or more and use a 30A fuse on the wire. Only fuse the positive wire. If you use a flexible copper wire, you need this AWG12 wire with this fuse. Read my article about selecting the right fuse and wire size.
Place the fuse as close to the battery terminals as possible. The manual of the charge controller will tell you what wire to use.
It should look like this:
Step 2: Connect Your Two Solar Panels Together
In this step, you will learn how to connect two solar panels.
This can be done in series or in parallel. I have written an article about the pros and cons of both of them. You can read it here: Series VS parallel for solar panels (opens in new tab). You can also check out my video about series vs parallel here. Here is the short version:
Always wire in series unless you expect shade on your panels. If your panels have shade, wire them in parallel.
Step 3: Connect the two Solar Panels to the Charge Controller and Battery
The wire from the solar panel will be too short to run to your charge controller. Use this wire to extend it so it can reach your charge controller.
Most of the time, you are going to use the series connection. So we will continue the example with the series connection.
Place your charge controller as close to your batteries as possible. Place your charge controller as close to the two solar panels as possible to minimize wire losses. If you have leftover wires from the solar panels to the charge controller, shorten them to reduce losses. Click here to watch my video about voltage drop in solar systems.
Your DIY solar system will now look like this:
Step 4: Connect the loads
If you have small DC loads, you can connect them to the load terminal on the charge controller.
I recommend using the battery terminals if you want to use an inverter.
See the following diagram as an example:
The diameter of the wires will depend on the current that will go through the wires. If the inverter uses 100 amps of current, you need to size your cable and fuse for that current. In my book off-grid solar power simplified, I go into a lot more detail on sizing your own solar system and wires. It’s available on Amazon in a digital (Kindle) and paperback version.
Conclusion
Connecting two solar panels to one battery is not that hard to do.
You need to follow these instructions on the page and use the wiring diagrams I have shown you.
If you have questions, email me or leave a comment below.
FAQ
How many solar panels can I connect to a charge controller?
The amount of solar panels you can connect to your charge controller depends on the power output of your charge controller. This is usually written on the sales page of the charge controller you will buy. If your battery bank voltage is higher, then you can attach more solar panels to it. We can see this in the datasheet for the EPever Tracer:
- Model: Tracer2215BN
- Nominal System Voltage: 12V / 24V DC Auto
- Rated Charge Current: 20A
- Battery Voltage Range: 8V-32V
- Max. PV Input Power: 260W (12V) / 520W (24V)
Can I connect two different solar panels?
It is not recommended to connect two different solar panels together. For more information, read my article about series and parallel solar panels or my guide about wiring mismatched solar panels.
Can you connect 3 solar panels in series?
Yes, if your charge controller has a high enough input voltage.
Use the Voc of the panel. In our example this is 21.3V, then multiply it with the amount of panels in series and a safety factor of 1.25.
21.3V x 3 panels in series x 1.25= 80VDC
This is under the 100V max input voltage of most MPPT charge controllers.
Can I use two solar charge controllers?
Yes, you can. Read my article about connecting two or more charge controllers to one battery.
I’m an off-grid enthusiast. I created this website to give clear and straight-to-the-point advice about solar power. I’m also the author of the book ‘Off-grid solar power simplified‘. Read more about me on my about page, check out my Youtube channel, or send me a message.
I see that you have fuse’s on the + side of the panel , what size should this be? I’m installing 2 -100 watt panel’s series, going to a Mppt charger controller,voltage 12v/24v rated current 40a,max pv voltage 50v max pv input power 520watt(12v)1040 (24v) I will be running a 12v tv / 12v light’s / and one 12v ex-fan . I have a 20 ft.run from the panel’s to the controller using 6 gauge wire, only 2ft from controller to bat. also should I hook the rv wire that went to the bat. before to the load output of the controller? Thanks so Much for your help, new at this , plan to full time, BLM land.
Hello James, your solar panel specification sheet will indicate the maximum fuse you should use. In this case, you cannot go from the calculations of your wire because voltage drop needs to be taken into consideration.
I’m installing 2-40watts panels in parallel can I join the before reaching controller then I join them as one in controller,then I have a 12v tv/12v lights
Hello Daniel, I’m not sure what you mean. Why would you put them in parallel? The wires from the solar panels go to the charge controller. Then your battery bank, and then from the battery bank or charge controller (low amps) to your DC appliances. If you use an inverter of high power loads, I recommend not use the charge controller load terminals. They are not made for high loads.
Can i combine a small and big panel together e.g 40w and 100w to one battery
Hello, I recommend getting the same panels to charge the battery. The best way to charge a battery using different solar panels is to use two charge controllers (one panel on each charge controller) who can communicate with each other so the charging current of the battery is split between the two. Victron charge controllers have this function. There may be more brands, but i’m not sure.
Hi Nick,
I am installing 2 x 380w panels in parallel on my caravan. I am using only 1 x 100amp Solar charge controller. In-line Fuse from controller to battery all on 8mm twin core copper.
My query will twin core 6mm copper wire be ok in lieu of 8mm?
Keep up the useful information, I have already learned heaps from your easy to understand explanation. Thanks again, Eddy
Hello Eddy, length of the wire is important. Use the voltage drop calculator I’m assuming the 380W panel has an Isc of 10A at 40V. Paralleling these two together will give you 20A at 40V. If we take a one way length of 10meters to the charge controller, then we need a 4mm² wire.
I want to buy 10 solar panels. I want to connect 5 panels in parallel to on controller and another 5 to another controller. Then hook them both to two 12v batteries in series for 24v. The panel specs are;
Rated 240w
Open voltage 37.2v
Max voltage 30.4v
Short current 8.37A
Max current 7.88A
Fuse Rating 15A
IP65 junction box w/ standard con
Is this possible?
Hello David,
1. Why do you want to wire in parallel?
2. What is the max input voltage and current of your charge controller?
3. Your charge controllers need to be able to communicate with each other to share the charging current.
I do not recommend this setup. I recommend 3 panels in series and then those three panels connected in parallel x3. For a total of 9 panels.
This will put your input voltage at 90volts which will max out the input voltage of the charge controller (MPPT) while limiting the current. Max current will be 24 Amps.
Can run 2 100w panels in series to a pwm controller? Or will 40v be to much for it?
I suspect it will be too high for a PWM charge controller. Refer to the datasheet of the particular PWM controller for more details. It’s best to wire your panels in parallel if you are going to use a PWM controller. Keep in mind the thickness of the cable that needs to be bigger.
Good day sir, I’ve got 2 x200w solar panels and 2 controllers, wondered if it’s fine to connect both cables from each controller to 1 battery 12v120ah and then add my inverter.?
Yes, charging one battery with more than one charge controller is possible. They will charge the battery according to the internal resistance of the battery. If the resistance in the battery increases, they will both charge slower. One charge controller might reach float quicker than the other because the software might be different. I recommend having your wires the same length.
I’ve a 100W solar panel on my motorhome with a PWM controller, I’m looking at getting a 200w foldable panel (maybe dokio) that I can put up against the side of the motorhome and angle it towards the sun. Is it feasible to put this in series with the 100w panel and connect to a MPPT charge controller ? I imagine I’d need to put in a multiway switch (If one exists) so that I could easily switch the connections out for the portable panel when not in use. Or is there another way I could do it?
I recommend getting another charge controller for your foldable 200W panel. It’s bad to wire a 100W panel to a 200W panel in series, you will lose half the power of your 200W panel. So, keep the PWM charge controller for your 100W panel, get an MPPT charge controller for your 200W foldable panel and connect them to the same battery.
Good day sir pls i connected 2 150w solar panel using d parallel method but it seems like d charge is not goin d way i expected but i saw on ur diagram “connection box” which i do not have could it be the reason ime having shortage of charge
2, do u recommend i use d series method?
The connection box is just a combiner box where you wire the wires together. Which charge controller and panels do you use?
Hallow sir,is the fuse must to be put when you connect panels in series?
Hello Julius, because in series the current stays the same, you need to use the fuse that is indicated on the back of the solar panel. If you connect two panels in series with a recommended fuse of 10amps for each panel, you install a fuse of 10amps for both of them.
Hello i have 2 panels 200w each and a SML 20A controller,
I’m planning to connect the two panels in parallel to the controller and then out to 4 x 12v batteries (Total 400Ah) connected in parallel also ,..
The point is that my invertor is 24v
What do you recommend the best way to connect it?
You need a battery bank that is 24V. Because the current to your battery will be 400W/12v=33amps -> you have a charge controller rated for 20Amps which is not enough. Same calculation with 24V battery bank: 400w/24v=16.6amps. So wire your batteries in series/parallel. Check here on how to put your batteries in series/parallel: https://cleversolarpower.com/batteries-series-vs-parallel/
Hi Nick,
Following up on my previous.
Would I be better off having independent feeds for each 380w solar panel eg: using 6mm cable with 2 x 40amp charge controllers. Space not an issue thereby eliminating back-feeding issues which I believe the controllers already do. Thanks, Eddy
Hello Eddy,
No you don’t need two separate controllers because your solar panels are wired in parallel. If they were wired in series, it would have been better for shade optimization. Parallel = 1 controller, series = shade loss or 2 controllers.
Kia ora Nick
Great site thanks. I have yacht with a wind turbine and solar panel and a dual charge controller for two wet-cell battery banks – motor and house. I’m thinking of replacing the house batteries with lithium. However, the charge controller is only rated for wet cell, but remotely controls the turbine, and I don’t want to replace it. Is it possible to have a second controller in series for the lithium bank? So one feed from the existing controller goes to the wet motor battery and the second feed goes to a second controller which charges the lithium house bank?
Hello Rob, If I understand it correctly, do you want to keep the same setup but use all the wet cell batteries for the motor? How can the charge controller control the turbine?
I would use the turbine to charge the motor battery and get a new charge controller which is compatible with lithium to charge the new house battery. I don’t think the motor battery has to be charged up all the time.
Hello sir, You are doing a great works thanks.
1. I have 300watt x 2 panel ( connected in series )
Now i have just gotten another a 340volt panel and 2 replacement batteries
i intend using 2 pwm charge controllers, how do i make the 2 controllers communicate and then connect it to 200ah x 2 batteries. kindly help with a diagram please.
2. my installer does not use any fuse in the initial installation either at the panel or at the battery area and this is 3years down. what are the implications. thanks
1. You cannot connect a 340volt panel to a PWM charge controller. I assume you meant Watts? Check out my article about multiple charge controllers: https://cleversolarpower.com/multiple-charge-controllers/
2. You need a fuse for every series string of panels. You also need a fuse on the positive of your battery. and the positive of your loads. The fuse protects the wire. If your wire gets too much current, the fuse will blow instead of the wire catching fire.
i need to connect a 250w panel and a 65w panel to one mppt charge controler 40amp to a 2 car 12v batteries is this possible ,can u explain how to do it please.?And can u tell me the result of watts and amps please?
Hello Brian, you cannot connect these two together to one mppt charge controller. If they don’t have the same current OR voltage. It’s best to each have their own charge controller. More information: https://cleversolarpower.com/multiple-charge-controllers/
hi nick tnx for your reply,just one more question ,if i use 2 solar panels same voltage and same current can i connect to one mppt charger?
I have 3pieces of 40watts,1piece of 20watts and 1piece of 10watts panels;12volts and 30amps controller
Advise me on how to connect them
Thank you
Without knowing the voltage and current of each panel it’s impossible to tell.
You have probably already answered this but I missed it.
1.) How many watts can a 10 Amp Controller handle?
2.) What size Controller do I need for a 200 Watt panel?
1) It depends on your battery voltage. A 10 amp charge controller at 12V can handle 120W. The same charge controller at a 24 battery bank can handle double, 240W.
2) A 20amp controller is your battery is 12V. If your battery is 24V, you can have a 10A controller.
Hello,i have two 100w panels,2 30A PWM controllers and a 3000W/24V pure sine wave inverter,and 2 deep cycle batteries for my camper.How do i go about connecting all of these and not destroy the inverter built into the camper for campground supplied power.
Connect the battery to the charge controller, connect your solar panels to your charge controller and use a precharge resistor to connect your batteries to your inverter. If you do not use a pre-charge resistor, there will be a big spark.
Hi Nick,
I have 2 x 200watts solar panel and 1 x 30 solar charge controller.
I have connected 2 x 200watts solar panel in parallel to 1 x 100Ah battery Whats the recommended inverter to be used?
Need your help to this.
Assuming you have a 12V LiFePO4 battery, I recommend using a 1,000W inverter if your battery is made for 1C. If your battery is limited to 0.5C, you can only use a 600W inverter. For lead acid (0.2C), the maximum inverter you should get is 240W. Check out my video about C-rate and my article about how many batteries for a 3,000W inverter.
Hello sir,
I have two 40watt solar panel and one 12V battery, one ss10L PWM conttoller. I have to operate my device on solar. My device works on 24V and also my device have one Internal battery. Kindly suggest me connection, please also share diagram. when I connect my device 24V connector in device motherboard, voltage iss dropped, not showing 24 V.
Kindly revert ASAP. today.
Thanks
Hello Sheelesh,
You need a 12V to 24V converter. There are many options available. Just choose the right power (watts).
If the voltage drops too much, your battery is not big enough to handle the power draw. You need to upgrade your battery to a higher capacity.
Lastly, your request to get an answer today is not appropriate. I’m providing free information, so I’m not obliged to answer you on the same day.
I have one 160 watt, MMPT panel connected to a MPPT 30 amp controller in a 12vdc system on my boat. May I connect a 100 watt MPPT panel directly to this existing controller? Must I provide another controller for the 100 watt panel?
You say you have an MPPT panel. Is there already a charge controller combined with the solar panel? If not, then I recommend reading my article about mismatched solar panels.
Hi Nick,
I have 2 solar panels with 120W 12 V, with short circuit current 18 V/SC: 7.02 A max. Current/Imp Power: 6.67A
I want to connect both solar panels in parallel and I’m using 20A PWM charge controller for this. What do you think?
Yes, that will work. Parallel is better for PWM indeed. Check out my article about the PWM efficiency.