What Size Fuse Do I Need For A 50w Solar Panel?

What Size Fuse Do I Need For A 50w Solar Panel?

So you want to know what size fuse do I need for a 50w Solar Panel? Gauging fusing for PV systems can be a bit mysterious if you are not an electrician. In this post I hope to take some of the mystique out of the task.

I will be presenting how to fuse both single 50w panels and when connecting together in series or parallel. Using tables I hope to simplify the process of working fuse sizing out. I will include the size of the solar charge controller and cable you will need to pair with a fuse.

But after reading my post. If you are still unsure you should contact an electrical or PV professional for help and advice. Because it’s all about keeping yourself and others safe around electricity.

So without further ado here goes ….. 

What Size Fuse Do I Need For A 50w Solar Panel?

“For a single 50w solar panel that you are not intending to connect to other panels in parallel. You should size the fuse to the solar charge controller. For example if the charge controller is 10A then the fuse you should use should be 10A. The fuse should not be placed between the solar panel and the controller. But rather between the battery and the charge controller”

What Size Fuse Do I Need For A 50w Solar Panel? - Fuse Diagram

If you are using a 50w portable solar panel and 10A solar controller to charge a house battery. For example a soft fold up like the ACOPOWER 50 Watt Foldable Solar Panel. You can buy the lead and crocodile clips separately with a 10A fuse already built in.

Here are some other examples of fuse sizes for different individual solar panel setups. Note this table is not for use if you intend adding further panels down the line in parallel.

Solar Panel Wattage  Solar charge controller Fuse Size Required
30 Watt5A5A
100 Watt10A10A
175 Watt20A20A
200 Watt20A20A
320 Watt30A30A

At this point you might be thinking why do I need to use a fuse at all?

Windynation Says;

The first thing to know is that fuses and circuit breakers are primarily used to protect the system wiring from getting too hot and catching fire. Secondly, they also are used to protect devices from catching fire or from becoming more seriously damaged if there is a short circuit. (Source; windynation.com)

What Size PV Cable Do I Need To Match With The Fuse For A 50 Watt Solar Panel?

This is a video from
Duet Justus about Solar Fuse Sizing And Wiring Charge Controller to Battery Bank

Just a quick note here with regard to wiring sizes. The thickness (diameter) of wiring in the United States is called the American Wire Gauge known as AWG. The rest of the world may use mm but most do use AWG.

The Importance Of Using The Correct Sized Wire

It is really important that you use the right diameter of wire with any solar system. This is because if the diameter is too small the wire will heat up and may cause a fire. If you think of your wire as a pipe and the current (amps) as water flowing through it.

Fuse Flame

If the pipe is too small for the water current flowing through it. Because of the water’s pressure it will eventually burst the pipe. In the same way the amps (current) will eventually burst the wire. But instead of spewing water everywhere like in the pipe analogy. The heat generated can eventually cause a fire spewing flames.

What AWG Of Cable Should I Use with a 50w Solar Panel?

Again I hate to go on but this is for use with a single 50w solar panel. Not if you are going to add panels to your system in parallel at a later date.

The calculation to determine this is rather complicated. It involves amperage, voltage, cable length and voltage drop so I wont present it here. But I have used this ready made calculator provided by Explorist.life and you can too !!

The recommended diameter of cable you should use with a 50 watt solar panel is 14 AWG or 1.63mm. This is assuming:

  • A 10 feet/3.05 meter cable
  • A nominal 3% voltage drop 
  • A 10A charge controller.
  • A 12 volt system  

Other cable lengths are shown below assuming the same parameters.

Length Of Cable Recommended Cable AWG  Recommended Cable MM 
5 Feet/1.52 Meters16 AWG1.29mm
15 Feet/4.57 Meters12 AWG2.05mm
20 Feet/6.10 Meters12 AWG2.05mm
25 Feet/7.62 Meters10 AWG2.59mm
30 Feet/9.14 Meters10 AWG2.59mm

I know 15 feet/4,75 metres is most probably the longest cable you would use with a 50w solar panel. But I thought I would present the longer ones just in case. 

I also know that the number of amps produced by a single panel is nowhere near as high as 10A. But the solar charge controller and fuse are 10A. So I thought basing the calculation on them wouldn’t be unreasonable.

Amp Meter With Solar Panels

You have also probably noticed that the longer the wire the lower the AWG meaning you need thicker cable. So to save money it could be worthwhile keeping cable length as short as is practical. 

If you want to know more about the size and specifications of a 50 watt solar panel you can find more information in my article;

Related >>>>>>>>>> What is the size and specifications of a 50 watt solar panel?

What Size Fuse Do I Need When Connecting 50w Solar Panels Together In Series? 

I am going to assume we are using 12 volt panels with a maximum output of 2.9 amps. I know that some of you reading my post are new to solar. There is a little bit of math here but it isn’t difficult to follow.

What Size Fuse Do I Need When Connecting 50w Solar Panels Together In Series? 

Stringing solar panels together in series incrementally increases the voltage. But the amperage stays the same. This means that if you connect 4 x 50 watt solar panels together and they are 12 volts each. The result would be a 48V system (12 x 4 =48). But the amps would remain the same 2.9A. 

This means you do not need to place a fuse between the solar panel and solar charge controller. Or increase the fuse size between the controller and the battery. It also means you do not need to change the AWG of the cables.

What Size Fuse Do I Need When Connecting 50w Solar Panels Together In Parallel? 

How Are Portable Solar Panels Linked In Parallel?

Connecting 50 watt panels in parallel is a different proposition when it comes to fuse size. Because when connected in parallel you incrementally increase the amps while the volts stay the same. So it’s the opposite way around to stringing in series.

This means that the amps will increase to 11.6A (2.9 x 4 =11.6) and the 12 volts will remain the same. It also means you will need to increase the fuse size between the controller and battery. It is best for system safety and protection to place a fuse between the panels and controller as well.

But you only need to do this when connecting panels together in parallel Alternative Energy says;

There are a few places in a solar system where you need to use a fuse, of which the main one is between the charge controller and the battery bank. However, you will also need a fuse between the charge controller and the solar panels themselves. (Source; altenergoptions.com)

What Size Fuse Do I Need?

You will have noticed that we have also increased the number of watts we are putting into the system. So now it is a 12V 200 watt solar array producing 11.6A. This by the way is within an amp or two a single 200w solar panel will produce.

What size fuses do I need for it? First of all a larger solar charge controller is going to be needed because a 10A isn’t going to cut it.

At this point it would be better to use an MPPT controller because it will provide higher efficiency then a PWM. We also need to add a 25% safety margin to the amp output to account for fluctuations. This would take the amp output to 14.5 amps (11.6 x 25% = 14.5).

What Size Fuse Do I Need?

Because we are using a 20A charge controller and the amps are 14.5A. You would use a 20A fuse between both the panels and controller and the controller and battery. 

The cable AWG would also change shown in the table below. I have used the same nominal 3% voltage drop I used in my previous example for a single panel setup.

Length Of Cable Recommended Cable AWG  Recommended Cable MM 
5 Feet/1.52 Meters16 AWG1.29mm
10 Feet/3.05 Meters12 AWG2.05mm
15 Feet/4.57 Meters10 AWG2.59mm
20 Feet/6.10 Meters10 AWG2.59mm
25 Feet/7.62 Meters8 AWG3.26mm
30 Feet/9.14 Meters8 AWG3.26mm

So for example:

  • The charge controller is 10 feet/3.05 meters away from the solar array you would use 12 AWG. 
  • The batteries are 15 feet/4.57 meters away from the controller you would use 10 AWG

Once again if you are unsure speak to a PV professional or electrician. It is always better to be safe than sorry.

If you would like to find out more about 50w solar panels amp production you can here:

Related == >>>>>>>>>>> How many amps does a 50 watt solar panel produce?

My Closing Thoughts

I hope that working out the fuse size for a 50w solar panel doesn’t now seem as mysterious. For a single 50w panel with controller and battery using a 10amp fuse is the way to go. But if you know about PV systems you will know that you can get away with a 5A fuse.

This is because even on a day with full sun and no clouds. It is unlikely a single 50w solar panel will produce more than 3A or so. This means if you are not going to expand your system at a later date you can use a 5A charge controller. 

I believe it is better to use a 10A fuse and controller from the start. Because it gives you the option of adding a second 50w panel at a later date. 

Plus you won’t have to change the wiring or the charge controller. As 2 x 50w panels pumping out 6 amps max connected in parallel. Is well within a 10A charge controllers tolerance. 

If you would like to take a peek at some 50 watt solar panel types, uses and specifications you can here:

I hope you enjoyed this post and have found it helpful. If you have any questions about 50 watt solar panels and fuse sizing. Or want to leave your own personal review, please feel free to leave a comment below.

Spread The Solar Love

8 Comments on “What Size Fuse Do I Need For A 50w Solar Panel?”

  1. I have been thinking about adding some solar panels to my home to help reduce the amount of electricity needed from the power plant. This information was very informative and will help me learn more about setting up a solar panel.

    Now I need to figure what size solar panels would work best for me.

  2. Hi Steve,

    I am not an electrical specialist and i am new to the game. i learn alot by doing things myself and if i dont do things myself and rather pay for a service provider (in this case an Installer) i atleast understand why things are installed or done the way they are. i learned alot about the fuses and the math behind it. i do have a question. For what purposes would you connect solar panels in series vs parallel?

    1. Hi Louis

      Connecting solar panels provides more power. For instance, 2 x 200w solar panels equal 400w. Combining the panels in series also increases the voltage, but the amps remain the same. Connecting in parallel increases the amperage, but the volts stay the same. 

      You can find out more about this by looking at my article:  Is there a way to link portable solar panels together?

      Hope it helps

      Regards

      Steve

  3. Hi Steve,

    You nailed it my friend. What a great guide to have my own solar generator. You put your effort to explain in details, materials to be used and emphasizing safety.

    Is there any governing laws in installing solar panel? Ordinary person like me can buy materials to be used for my own solar panel generator?

    Greatly enjoy reading/studying your post. If given a chance I will built my own solar panel power supply.

    Cheers,

    Al

    1. Hi Al, 

      As a 50w solar panel is undersized, you would only use it for installation with smaller projects or portable use. I don’t know where you live, but it is always worth checking local building regulations for prohibitions or permits.

  4. Hi – really hoping I can get a straightforward answer to what I think are pretty simple questions. So far I’ve had no luck with this elsewhere.

    I’m looking for the right size charge controller and information on what I need in the way of fuses to safely and efficiently run a small 12 volt exhaust fan and occasionally used LED light in an off-grid greenhouse. The panel is 50W. My hope is to use a a basic 50AH lead/acid car battery to keep the fan running in the summer months when it could get and stay too warm in the greenhouse after dark when the panel is no longer charging/running the fan. Daylight hours in the summer here are from about 5am-9:45pm in July and August.

    A 12V 50w solar panel that came with a 12″, 4.7 amps exhaust fan I am using in the greenhouse. The fan has a thermostat attached between the solar panel and the fan itself – it is internally set to go on at 85 degrees and off when the temp in the greenhouse reaches 65 degrees. I live in the Pacific Northwest, so the greenhouse heating to 85 for extended periods of time are limited to sunny days when it’s 65 or above. In the summer, cooling the greenhouse could mean the fan may be running from morning until past sundown and up to 11pm. Since the greenhouse can get condensation on the roof panels and drip a bit, since there will be humidity in the greenhouse, a waterproof charge controller would be nice.

    I want to plug in a small 1.6 watt USB LED light to be used rarely and with its own power switch, so it will only be on at will and not often at all, so the charge controller should have a USB port.

    What size charge controller do I need? What type of fuse set up do I need? What kind of wiring do I need?

    I look forward to your response. Thank you!

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