How to Fuse a Solar Panel Array for a DIY Camper Electrical System 

This is why I do single series string arrays haha I never put panels in parallel these days for this reason. I am too lazy to wire up a ton of breakers. Super good video! I will just direct my viewers to this video. Thanks

Excellent description explaining what was, at first, completely over my head. You are an excellent instructor sir! My journey through your series continues!

Glad to see another video !! This gives me something else of yours that I can share when people ask me questions about setting up electrics/solar/wiring/etc.. in a van.

Awesome! As an Electrical Engineer, I am quite impressed with your knowledge. Thank you!

I just wanted to thank you for your efforts in explaining how to wire up a van. I have been watching your RU-vid channel for about two years on how to build a van. I use to have a 5th wheel, but when I retired from being a higher education IT system admin and fix it all networking dude on 1/31/2020 my wife and I decided to get a van instead of another trailer. So in April 2021, we bought a 2017 Ford Transit 350 PowerStroke high-top extended. I downloaded your plans to add to my collection of two other van plans. I wanted to support folks who take the time to share accurate and easy-to-understand information. So anyway, I have a lot of van equipment in my dining room. I am working to get a minimal install in the van for our first trip in September. The van is not going to be completed, but I have a sliding bed and I installed two MaxAir fans. I told my wife that my goal was to get the fans installed, have a bed, and have batteries charging off of our van battery. When I was watching your Airstream build for the third or fourth time I realized that I had calculated my solar incorrectly and I had to order a different solar charge controller. I like the way you explain things in detail without glossing over what is important. Thanks again for all of your hard work.

Ask far your videos are the most complete and simple to understand I’ve seen. Thank you!!!!

Wow - I have been figuring this whole fuse issue wrong. Thanks so much for posting this information.

OMG!!! Your presentation has just cleared one of the biggest confusion i have been having on PV module installation . Keep up the good work. Thank you friend

These videos are going to save me a lot of anxiety and trusting others who may or may not be competent. Thank you so much for producing all of these instructional videos and blogs.

You make so much sence. I really don't need another source of information. Thank you from South Australia.

Your videos are so complete and so easy to follow! Thank you so much for all the time you spend making them.

Thank you for all information! Congrats from Brazil!🇧🇷

Amazing videos, I've been looking at battleborn batteries and some local suppliers of panels to try and offgrid some appliances but there was so much information and much of it conflicting. This entire series puts it all together in easy clear ways with fantastic visuals!

Enjoy ur vids, ur a great teacher, good info & content. Cheers

This was very helpful. Thanks!

Hey Nate, As I watch your videos to better my solar education, my girlfriend is listening in the background. She made a comment that should flatter you and your channel. She stated that your voice is soothing to the ear with good clearity and great vocalization of your words. Anyhow that tou should know. Love your channel

I think this answered the question I posed to your other video. 🙂

I must say, (and this is NOT a brown nose exercise) I find your PV calculator the easiest to use BY FAR

If you are providing good content then you deserve all the ad revenue you receive.

Very well explained thank you.

Thank Nate, understood after a few repeats.

This information is awesome, thank you!

Thanks Nate! I have 2 panels wired in series with no fuse. I THOUGHT that would be ok, but now I have the data to back it up.

Great to see you're back Nate! Your videos regarding solar anything are absolutely the best. Additionally, the interactive diagrams and associated ordering list are waaaaaay cool! Hope you and Steph are doing well.

Great videos, they are very helpful. I especially like the way you break things down into appropriate bite-sized chunks 👍 That said... I think you may have wrong video linked in the show notes for determining short circuit current. The URL provided goes to the series-parallel video a couple of episodes back, not the one linked elsewhere from fall 2019. A minor quibble, otherwise you're doing great!

Keep up the good work!

Great explanation for a very confusing subject.

Something I agree on. Thank you for enlightening the DIY group. I have yet to get serious about the 4S4P solution with my panels and inverter. I have a Growatt 80A with a 60-145V range. The panels are 260W 30.6V 8.5A and knowing the fuse solution leaves me cautious with a 3S2P. I could do 4s4P-5P even. 122.4V at 34A - 42.5A but then where goes the fuses? Brave men burn down their homes. I shall wait until I've absorbed more knowledge. Of course, there is always the wire to consider.

Nice info, thanks.

Excellent explanation.

most helpful tips.thnx..

Great timing. This video I hoped would clarify, but, maybe it went by me too fast? I'll read the blog post too. Thanks. I was in the process of fusing my Lynx distributer, I'll send those Q's to the EL private crew.

Yes, but HOW do you know what your TOTAL short circuit current is of your entire array? Do you add up each one in series or parallel?

THANK YOU for these extremely instructive videos! They've given me enough knowledge to get most of the way into design on a motorhome roof 1200W 12V array. Panel: Newpowa 210S-12H. Vmp 16.77 V, Imp 12.48 A, Max Ser Fu rating 15A. Two 3-panel banks, S/P I see (2) series circuits producing 50.31V @ 12.48A. Paralleling them I calculate final out of 50.31V @ 24.96A (not adding for temp). Do I understand correctly that I need to fuse before or after the Y branch parallel cable(rated 30A) up on the roof, and if so, what fuse size in each leg? (figuring the Isc for the entire array is 39.27 x 1.25=49.1A and the Max Ser Fu rating is 15A) I'll be dropping to a breaker/disconnect before the Victron MPPT 150/85TR.

Thanks

Impressive...cool

You just saved me from doing it wrong. Thanks!

Your awesome

Hi Nate, Do short circuit issues only apply when panels are in parallel? I read all (most) of the comments before asking and it is not explicitly stated, but implied by several messages and your graphs. This is my understanding so far; a) Panels in series - no issues since amps are not added (only voltage is added in series). b) Panels in parallel - fuses may be required since amps are added (in parallel) and total amps may exceed short circuit amperage rating of of the panel (fuse rating). c) Panels in series-parallel - fuses may be required for same reasons as above. It appears only the panels in parallel when the amps are added is where the fuse question becomes an issue. Can you clarify? BTW, you have the knack for educating people on complex topics. Strong work. Tim

Let's see if I understood correctly: I have two panels connected in parallel both with short circuit current = 10.269A, would short circuit current be added, too, for a total of 20.538A? Max series fuse on the panel is 20A, so would I need a 20A fuse on both panel's positive cable before they go to the parallel connector? Loving the videos btw, I'm learning a lot and found I did a couple things right on my starter system!

Hey Nate... nice video... thank you for sharing. Speaking on sharing... would you share with us the excel spreadsheet ?

Good videos I have learn a lot question I am starting a system for my cabin have 4 panels 300watts each panel is better parallel or serial

Hi, you make one of the best learning videos. Question for you, on the back of my panel, the max series fuse rating is not written, Do you know how to get it if it's not possible to talk with the fabricant?

Hey Nate, watched a lot of your video's your doing a great job. I have a 76 GMC RV the electrical is totally trashed doing a complete rebuild but don't want to do the solar quite yet but want to have a build that will be able to add it later I like the smart inverter (that uses battery power to top up when shore power is not enough) plan to go with 3 lithium batteries and have a 3000 watt inverter generator and like the idea of charging with the alternator too do you have a list going for a build that leaves the option of solar later?

I don't have an RV but solar power is quite interesting.

Hi! Thanks for the video. I am far away not an electrician. What would be the functionnof the bypass diodes on the panels? Is there any additional protection from the inverter side? Thanks

Hello Nate, I am a new subscriber and find your videos very informative. I have a question about fusing. Do two 160 watt solar panels connected in parallel have to be fused. Both have a short circuit current of 8.37 amps, optimum operating current of 7.92 amps and a max. series fuse rating of 15 amps? I think the answer is no, but not sure. Much appreciated, thank you.

I am using the same Rich Solar 200w 12v panels as shown above. They will be wired in 3S2P. Each sting will produce the 9.8a but the strings when parallel will be 19.6a exceeding the individual panels 15a max fuse rating at the combiner. Where (if at all) would I fuse this array and what fuse capacity would I use? This is an amazing video btw. Thanks for all you do. You and Will Prowse have become my Gurus.

You're presentation of what the current does when a short appears in 3 panels connected in parallel was very helpful. Thank you, thank you, thank you! But once I understood it, I tried to apply that reasoning to the 3 panels in series and got confused. I came to the conclusion fusing in any pure series arrangement would never be needed since the currents never add. Is that right? (Still learning...)

Hello, nice video. ISC of my solar array is 22.44A Maximum series fuse is 20A Must I put 20A fuse on each Double 2 in 1 MC4 combiner? Thanks in advance

When is the "next video" coming out? I am looking for info on the breaker between the solar panels and the charge controller. I checked your web page but did not see an article there yet either. Looking forward to it !

Thank you. I don’t need my inline fuses then.

HOWdy E-l-DIY-C, ... Thanks COOP the WiSeNhEiMeR from Richmond, INDIANA ...

So, my solar setup doesn't require fusing based on your video. Does it also not need a DC breaker? Could I just use a DC isolator? Love your content - thank you.

Great videos. Best help I have found. I cannot figure out the fuse between battery and controller. Manual of Renogy Rover 40 amp Mppt states to match the rating of the controller, so 40 amps. I am running two 160W renogy flex panels in parrallel. 8.88a short ciruit current. 20 amp Max Series fuse rating. Is it even possible to achieve 40 amps of current with that setup? Thanks for what you do!

Great video. Love the schematics. May I ask what do you use to draw them.

If Voc panel voltage is an issue, i.e., it exceeds solar charge controllers max input voltage, does it make some sense just to install an additional MPPT vice putting up to parallel wiring issues?

what about matching panel VOC to the controllers stated maximum VOC input ?

are these concepts usable with home installation

This might seem like a silly question.. I am getting ready to install my panels. I plan on adding tilt bars, does it matter when laying them out if they tilt lengthwise vs width? If I lay them out to tilt up lengthwise (taller vs wide) I can fit more panels in the future. I can still fit all 4 width wise but it leaves little room for expansion later on down the road.

Hi Nate, we are wiring 840 watts of solar in series/ parallel and am wondering if our short circuit amp is 10.86 per series would we only need a 15 amp fuse or 20 amp fuse? our specs our for a 20 amp fuse. Thanks

Do the fuses in a combiner box pretty much do the same thing?

I am looking at a 600 watt solar array. (sailboat with some shading possible) 100 watt panels. 2 x 100 watt panels in series. the the 3 sets in arrays. The panels have this rating: Open circuit voltage 21.6 V Maximum power point voltage 18 V Short-circuit current 6.11 A Maximum power point current 5.55 A Would I need a fuse in this scenario? the set up i believe would be: SERIES PARRALELL 3 solar banks (each 2x100 watt panels) 3 - 200 watt solar banks in series then parallel 600 watts (40 volts at 15 amps) 100/50 charge controller 10 Gauge Wire Am I correct on all this? These videos are AMAZING!!!!! Best Ive seen

Thanks so much Nate for all the immensely helpful videos you have made... Question for you... in Case study #1 at 3:18, you show panels A, B, C where C is the right most panel and it has a failure causing it to short out. From Kirchoff's current law, you get the 20.4 amps (total from panels A and B) going through panel C. The part I am unclear on is you show the total potential current thought panel C at 30.6 amps. In a real world scenario, if though panel C has a failure (e.g. short), it is *possible* for it to still be operational to produce current? I have no knowledge of the mechanism of solar panels and hopefully I will learn something but it would seem if the panel fails, it wouldn't be capable of producing current. However, even if the 20.4 amps were the only current, based upon your example, the fusing would still be required. Thanks!

What do you use to make your wiring diagrams? Always so clean.

Hi Nate, thanks for the very informative videos. Could I use the x 1.25 rule to size the fuses for the panels? I gather you use the maximum fuse rating as the panels components can handle that amount of current and is probably simpler to do, but I've already bought a bunch of 10a fuses for solar panels with a 5.51a short-circuit current, would they still be ok to use? Just out of interest, why do you place the fuses before the branch connectors and not afterwards? Just I noticed alot of places like Renogy specify placing fuses after the branch connectors. Does it mean that in the case of a short circuit and the fuse is blown, that just the one panel would stop working rather than all 3 tied into that branch? Many thanks in advance! Joe

Nate....all great info...quick question on future solar expansion...any reason to not oversize solar controller with expansion of panels and batteries down the road...?

So I have 8-200 watt rich panels that I plan on wiring in 2 series strings then connecting those in parallel so I can max out my watts input for eco flow power station. The short circuit current for each panel is 10.2. So that would stay the same for each string but when I wire them in parallel it would then be 20.4. Would I need to fuse these at the Y branch connectors?

Fusing is confusing! Thanks for everything you do to teach us what we don't know. I've learned so much. 2 quick questions: 1. If I have 5 panes in series and each has a fuse rating of 15amp then I don't need a fuse. However if these panels are 20amp fuse rating then I need a fuse? 2. How about between the MPPT Charge Controller and the batteries, do I need a fuse between them?

The example you first showed if it was wired in series parallel what it need a fuse? - I am doing exactly that, 4 12v 100w panels in series parallel,

Great Video, Can I please ask what software do you use to make the diagrams? I would like to design my own system and looking for the software to do sketches.

Hello, thanks for share this video. BTW how did you build that pretty diagrams, can suggest any software for do that?

*quick rundown* I have 4- 100w panels, p30L charge controller, 2- 200AH deep cell agm batteries, and a 1000w pure sine wave inverter charger, with 4 outlets run in parallel, that will be hardwired into the inverter charger. Do I need a breaker box anywhere? Or will properly placed fuses between components provide adequate protection.

Hello Nate , Being consistant with your example of the panels in parallel , with those same specs can I use a 16a breaker on each panel .

Awesome information. Appreciate all the work you do. Quick question, I have 4 550w panels I plan on adding to the top of my bus. I need help determining between parallel or parallel series, and then sizing my fuses. IMP: 13.11 VMP: 41.96 ISC:14.01 VOC: 49.9 I cannot find max series fuse rating ANYWHERE, only maximum system voltage which is 1000 I calculated the short circuit (14.01) x 1.56= 21.86.. so if doing parallel I would need 30a inline fuse prior to the 4 to 1 mc4 connectors. What I then am getting confused about is after the 4 to 1, that would be (21.86 x4) 87.44 amps running thru that connector and would not be able to handle it, right? Or would a 100am pv isolator be after the 4 to 1? Any and all help would be appreciated.

It sounds like fusing in parallel is just a good thing (cost vs possible repercussion)

Question: when figuring out if you need fuses and also wire size, do you use the stc wattage, or the maximum wattage for calculation? I have renogy 115w bifacial panels that have a max power stc of 115w, but it has a capability of 149w under optimal conditions. So in my calculations do i calculate using the 115 or 149? Thank you and I'm glad i found your channel as I've been struggling getting a straightforward answer on many applications even from renogy customer service itself.

Hi Nate, I"m having a hard time finding the max series fuse rating for my panel as it's not on the back sticker and can't find it on the manufacturer's website. Can you help? Newpowa model NPA180S-12H (180W mono). Thanks!

Thank you Nate! I am actually learning this and I took the quiz on your blog and only missed one, the last one. This is my 4th time watching this video and it makes more and more sense each time I watch it. I am figuring this all out, however, my Newpowa 180w panel only has 5 of the specs on the back. It does not have the max fuse series rating. It says: Short circuit rating of one panel is 11.75A, exactly what is a short circuit? (the path of least resistance explained here?) Second, how do we figure that out if we have two panels(if wired in parallel short circuit is 11.75A +11.75A , if wired in series it is just 11.75)? That is where I think I am on the right track..btw I only have one panel for now so my 30A charge controller doesn't need to be fused. I want to purchase another, but not without being sure that short circuit means what I think it does. Am I on the right path?

I have 1 string and a fuse on both poles right before the DC over voltage shunt so if Lightning strikes and the over voltage gets tripped i hope the fuses blow BEFORE any fire starts or the inverter blows up. Grid tie Solar Edge inverter and panels. Don't "need" it but want it 😁

Idol how about in batery connection.parallel connection also need to fuse?if how.thanks

Hi I have 2 parallel solar panels running to my victron 100 20a than to my battery box the battery box has a 16a circuit breaker do I still need to put a fuse on my battery box

What do you do if you have to parallel different panel models? Example, 3 40w with 1 50w? And what if the "maximum fuse rating" is not written on the panel?

Great video as always. Sorry if I missed it but I didn't see how you compute the Short Circuit Current of one's solar array when there's more than one panel. I've got 4 panels, 2s2p. Each panel's ISC is 9.85A, with a max fuse rating of 20A. (Hightec 210W panels). Do I add the ISC for all four panels to compare to the max fuse rating or just for two panels (since we don't add Amps for the two sets of series panels)? Thanks!

So if I am doing 5 panels that are 9 amps in series and doing two sets of those in parallel what do you recommend for fusing? Do I need to fuse if my wire is 6 gauge and can handle more amps and such. Curious anyone I’m setting up a lv6548 soon so I am researching proper fuses and wires to run 150 feet to batteries

Great video. May I ask which tool you use for those drawings? Thank you

First of all, thank you for your videos. I have eight 400 watt Solar panels, the Voc is 49.3 volts. my charge controller is a tracer 4215 BN maximum voltage 150 input. I am running an off grid 12 V inverter to make my 120 v. My question is, will I need 4 charge controllers like this one to handle the solar panels and stay with 10 gauge wire. I think that’s what I have to do..I’m just double checking. Thanks, Rob

GREAT VIDEO! It seems very hard to really get that design conversation laid out for discussion... One Advanced Question I have on that "in-series" fuse layout Idea. Let's say you have two in-series banks, each bank is 3 panels and each panel has an open c. volt rating of 49.8v and a short c. amp rating of 10.36amp, and directly at each panel connection in the series you use an MC4 connector that contains a cheap replaceable 15amp fuse so that it is closest to the source and slightly greater than nominal just in case one panel has a short circuit problem preventing damage to the rest in that series, if one single fuse (6 total) blows I believe that shuts off that entire 3 panel series, but my question is.. since that series is parallel to another 3 panel set will it cause any issues using the remaining 3 panel series for charging at only 10 amps and 150v, vs 20amps at 150volts? I know some MPPT chargers want sufficient amps to even begin charging efficiently. I have periodically detected some volt fluctuations back fed up the wire when only charging 12 volt batteries using this array when only one series is switched on, so either its a MPPT charger issue or this tiny fuse "in line" in a series is a bad idea for some electrical current reason.

Hello my hero, would you sell me a complete system setup on a board for an off grid installation? Thank you and please keep up the good work

question for you, i am finalising wiring this weekend for a friend of mine he has 2 identical longi panels installed on his shed roof both 445w rated max power,the have a max short circuit current each of of 11.53 a,, current @ pmax of of 10.78 amps, max system voltage of 1500v, max series fuse rating of 20 amps, we wish to wire both together to get the most watts/amps out of them (the voltage pmax is 41.3v ), they will be feeding to a string of 8 12v batteries and in turn the 12v power will be feeding to a victron quattro 12v 5kva system, what fuse do i need i am confused by the series/parellel and the info on the labels ?? pps , these are new current generation Longi panels about 3 months old, they are currently both seperate running 2 charge controllers,here in the uk dc isolaters are super expensive, i was going to use standard mcbs of the correct amperage on both lines to act as a dc isolation, is this right/wrong ??, i have the victron putting out 240v ac with no problem off of 2 rolls batteries that are currently contacted, the remaining 6 lead acid 220ah batteries will be wired for 12v this weekend on the second dc in line on the victron, the victron has a main off box(external to the unit) with 2 lines each already fused with mega fuses of 500 amp times 2, which according to the victron specs exceeds the 800 a min fuse rating, please help :) :)

Question : I am installing 6 x 150w solar panels to my bus in parallel. each panel has a 15A rating. Am i right in saying I DO need individual fuses installed for each positive connector? Thank you in advanced :)

Shouldn't we compare the Max Series Fuse rating with the corrected short circuit current? By corrected, I mean taking into consideration the temperature coefficient effects (or a factor of 1.25 for over irradiance) and possibly another 1.25 factor since it's a continuous power. Since the I_sc rating on the PV panel's label is under standard test conditions.

Hi I want to make a setup with 6 solar panels total. They will goi either in 2s3p or in 3s2p. The maximum series fuse rating for the 1 panel is 15A, my question is, if I go to the 2s3p configuration or the 3s2p what kind of fuses should I install? Thanks for any help.

I have one panel that’s 15a and came with the rv and adding two more that are 20a rated. All are renogy 200 watt panels, would I use a 15a and 2 20a fuses or make them all 15a? Im not very good at this 🥴

Hi Nate, From Puerto Escondido Mexico, we follow you! Question: What Size of PV Brearkers I need to use for a Panel Arrey that it has 2 Panels en Series and 3 Strings in Parellel, this is the info for the Panels, Short Circuit Current (Isc)14.01 A, Open Circuit Voltage (Voc)49.68V, Maximun Power Current (Imp)13.42A, Maximum Power Voltage 40.98V And Maximum Series Fuse Rating is 25A, Thanks for your Time and Help in Advance. Juan Martinez.

Ok so if i got this right i have 2/100w panels @5.5 a short circuit ratings each. A 10 amp fuse each panel is what i need wired in paralell?

can i do this set up but just get a normal inverter and converter instead of the inverter charger you use? would i then have to change where my shore power runs to??

What size fuse is needed? Is the fuse for each panel the same size fuse as the max fuse desciption on the panel and then how do you size a fuse into an array ? I got Short Circuit Current 11.39amp and Maximum Series Fuse as 20 amp, 2s2p . Will i use 20amp fuse in each panel and 40amp fuse in each series fuse then into the charge controller??

my solar controller is a renogy 100 Amps and pure inverter 2000w renogy have eight batteries 192 amps gel planning on installing them on 24 volts series batteries based on your knowledge is this ok or you suggest something different, thank for your input lived up north in Canada not much sun in the winter in ONTARIO

Hey Nate I'm still a beginner and some of this went right over my head 😳 Any who can you tell me if I need to fuse these two panels for my solar generator in parallel? JA SOLAR JAM54S31-395/MR RATED MAXIMUM POWER (Pmax) [W] 395 OPEN CIRCUIT VOLTAGE (VOC) [V] 36.98 MAXIMUM POWER VOLTAGE (Vmp) [V] 30.84 SHORT CIRCUIT CURRENT (lsc) [A] 13.70 MAXIMUM POWER CURRENT (lmp) [A] 12.81 MODULE EFFCIENCY 20.2 The specs reads as: Maximum Series Fuse Rating 25A not sure if this is what you were referring to. Thx!