How to Connect two Solar Panels to one Controller and one Battery

Connecting two solar panels to one controller and one battery is very easy.

This article will explain to you how to do it, including a circuit diagram.

Step 1: Connect your battery to the controller

The first step is to 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 the current that your charge controller is going to send to the batteries. For example, the Renogy Rover 20A delivers 20 amps to the battery. You need wires that are able to carry 20Amps or more and use a 20Amp fuse on the wire. Only fuse the positive wire. If you are using a flexible copper wire, you need this AWG12 wire with this fuse. Place the fuse as close to the battery terminals as possible.

You should end up with a setup like this:

connecting one charge controller to one battery
connecting one charge controller to one battery

Step 2: connect your solar panels together

In this step, you are going to connect your two solar panels together.

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. Here is the short version of that article:

Always wire in series unless you expect shade on your panels. If your panels have shade, wire them in parallel.

Connecting your two panels in series will add up the voltage, while parallel will add up the current.

If you wire in series, you need a smaller diameter of wire than parallel. See the following circuit diagram on how to wire them.

series and parallel connection of two solar panels
series and parallel connection of two solar panels

The fuse rating is specified in the solar panel datasheet or on the sticker at the back of the panel. You can use an inline MC4 connector fuse.

Step 3: Connect the two solar panels to the charge controller

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 wire from the solar panels to the charge controller, then shorten them to reduce losses.

Your DIY solar system will now look like this:

how to connect two solar panels to one controller and one battery
how to connect two solar panels to one controller and one battery

Step 4: Connect the loads

If you have small DC loads, you can connect them to the load terminal on the charge controller.

If you want to use an inverter, I recommend using the battery terminals.

See the following diagram as an example.

connecting loads to one battery
connecting loads to one battery

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 fuses for that current. I go into a lot more detail on sizing your own solar system and wires in my book off-grid solar power simplified. It’s available on Amazon in digital and paperback version.

Conclusion

Connecting two solar panels to one charge controller and one battery is not that hard to do.

You just need to follow these instructions on the page and use the circuit diagrams I have show you.

If you have questions, make sure to send me an email or leave a comment below.

20 thoughts on “How to Connect two Solar Panels to one Controller and one Battery”

  1. 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.

    Reply
    • 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.

      Reply
    • 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.

      Reply
    • 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.

      Reply
  2. 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?

    Reply
    • 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.

      Reply
    • 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.

      Reply
  3. 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.?

    Reply
    • 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.

      Reply
  4. 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?

    Reply
    • 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.

      Reply
  5. 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?

    Reply
    • The connection box is just a combiner box where you wire the wires together. Which charge controller and panels do you use?

      Reply
    • 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.

      Reply
  6. 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?

    Reply

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