How to Size a Solar Charge Controller for a DIY Camper Van Solar System 

So, Nate. 2 years later, and- here I am sitting, watching & feeling incredibly grateful! Not only are you highly focused, right on stream & quick (thank you!) but, additionally, you use Victron equipment (mine's marine- Victron required-almost!) and explain detail (fitment, temp. ranges, max voltage). Finally, space restrictions, wire runs, proper contacts at equipment- all priceless details that PREVENT releasing the magic smoke inside the wires & charge controllers (That's my biggest worry, can't put the Genie back in the bottle once it's been freed!) Wow, I wonder how many people have been helped with you & your wife's channel? I bet it's up to tens of thousands? Free calculators, Excel spreadsheets... Thank you is certainly NOT enough.

How this video has so few likes is beyond me. This calculator is amazing! Thank you for putting it together.

I been looking for this kind of information without the bs glad I finally found you.

Thank you for being an AWESOME teacher. We are in the beginning days of building our Shuttle Bus and your videos are helping us understand solar and what we need to purchase. Sincere Thanks.

The calculator is awesome and might really save some people a lot of headache and money from unknowingly undersizing their charge controller! Not to mention a lot of RVrs may find themselves in high altitude situations where cold weather can come during times of the year when the sun is high in the sky!

Thanks for the info, we are off grid “Victron gear” I constantly monitor our usage and as you say the difference in winter / summer is easy to see when looking live on the VRM, we have a duel axis array setup, consists of 6 x 335watt LG panels in 2 strings, (2010 watts total) it’s looking at the sun all day sun up - sun down, I have seen in colder days it reach 2430 watts, on real hot days eg: 39c it only pumps out 1700 watts, big difference, MPPT is 150/100. Inverter charger Mulitiplus 48VA - 35Amp. Batteries agm 12 volt -220AH x two banks (48volts) It gets us by no problems, il be using your method when upgrading later. Thanks again👍🇦🇺

Great video! Just the right amount of focus, math and repetition for me to learn it. We all learn differently, and after watching countless videos from other channels this is the fellow that explains it just right for me to understand and learn.

Your content is simply amazing!! I stumbled upon your channel trying to learn more about a solar install into a skoolie, and every video you've posted is so far invaluable to me. Cannot thank you enough for making all of this so accessible

You should thank yourself. This stuff is a bit complicated when someone like me has absolutely no knowledge to start with. I've saved your video and worked out some numbers just to follow your demo, but I know when I get ready I'm going to want someone like you to double check my numbers. This won't be for 3 years when I retire. So in the mean time I'm going to be the most informed as I can be from rooftop to floor. You have been a big help. So thank you, i appreciate you. Pattie

Thanks for the succinct information and the calculator! Greatly appreciated. Using this info to "check" the contractor we are working with to ensure we are not being under/oversold.

I will be upgrading my truck camper to a Lithium system and came across your videos. They are helpful beyond words!!! Thank you!

Just completed first consultation last week I learned so much create safety in the system I have and allow more efficiency I would recommend consultation to anyone seeking to do their own solar system It is Well above worth the money I promise the best absolutely the best thank you so much

Sorry, but on the current calculation you multiplied by 5 at moment "6:04" but you should take into account that the maximum current is only 9.22A as the panels are connected in series. Thanks for the video!

Way awesome, THANK YOU SO MUCH FOR WHAT YOU DO! giant help

This video and your tutorial is excellent. Thank you. I'm currently at the planning stage and your knowledge and calculator will be essential in planning my setup. I am planning on using Victron totally. Once again; awesome video.

Finally found the info I was looking for regarding multi panels and the Victron MPPT 100/20. Thank you

Great video! I am on a sailboat and your calc is great. Your stuff is great for the 'floating' RVs:)

Holly crap. That was an extremely well done explanation. I understood ! Of course by the time I add the period I will have forgotten everything, but that’s not your fault. Great job.

thank just kidding you have learned a lot since your 1st video nice to see you have turned a hobby in to a business good for you good luck in the future

top notch dude..thankyou for Yoir time and effort..much needed help..big ups ..THANKYOU

You just saved me a bunch a digging around. I was searching for the right size charger to connect to a 540W panel. Thankyou Thankyou Thankyou.

Fascinating video and your calculator is amazing. I only have a small teardrop camper with 100 W solar but I want to upgrade my batteries to lithium and the charge controller too.

just sad. i just happened to run across your channel while researching solar set ups for travel trailers ( glad i did by the way ) and i can't believe the dislikes !! why?, it seems the more information you give, the free resources, the time it takes to make videos of this caliber, everything short of doing it for them, people still have the nerve to thumbs down videos. you even take the math ( which is complicated for some ) and break it down to make it a heck of a lot easier. i just don't get it. thanks for all your hard work ( i know i appreciate it ) , read a few articles on your site as well... added to my favorites!!!

Your calculator saved me from making a grave mistake. A self-proclaimed solar nerd convinced me that his math was correct. It turns out that my amperage was WAY higher (42 amps) than I should be running. Thankfully, I had doubts. Liked and subscribed.

Thanks for providing this information and calculator Nate!

I’ve just found your channel and it’s gold dust. Please keep up the fantastic work.

Wow thank you so much for the quick to the point info and the tools you provide are awesome.

Really incredible. Thank you!

Wow u draw such straight lines and square corners :)

cool. idol! yeah i found vitron product complete on this camper projects, i am planning victron all the way.. love ur content, mathwhiz!

The diagrams are JAW DROPPING

Just learned that I need a way bigger controller for my set up than I ever imagined. This saved me money in the long run, as I will not blow the puny one on an over voltage/amperage. With those 4x65W panels x 2 series it turns out I will have to go for a 150/60 controller.

Great info, thank you. What I find missing in all these videos is determining the most efficient way to charge a battery, meaning not only the charge controller selection, but the various segments of wire and the guage. I think this is a safety issue as much as anything else. For example, is the fastest way to charge a battery higher voltage or amps? And once I have the charge controller and panel arrangement figured out, what is the most efficient (and safest) wire guage and type to use? I've yet to find a comprehensive video that help with that.

Great video - you threw me off track with the Max Power Voltage (i.e. 22.65Voc Vs 18.90 volts) Had to go back to look at the solar panel label again to verify. Thanks for the videos - much appreciated!

Correction needed Hey Nate. I would like to thank you for your time and effort to upload all those informative videos, keep it up. When it comes to calculating the Max Amps coming out from the MPPT solar charge controller the answer in your video references the max wattage you calculated with the formula divided by charging voltage pushed, where as in the calculator on the website it references the Max Voltage Per Panel at Estimated Low Temperature x Solar Panel Maximum Power Current (Imp) / Charging Voltage Pushed the two approaches are different and lead to different answers… I think something needs to be fixed.

Hi Nate, Thank you for this, really helpful. My calculations based on the info you mentioned. I get 43V and 52Amps... This is based on a minimum temperature of -20ºC... Would the 100/50 MPPT be ok, so should I really need to go larger?

you are a great guy and a good teacher thanks, god bless

Hey Nate. Thanks for the great information. Looking at my rich solar panels, some of the verbiage in your calculator isn’t the same so I’m not sure if I’m putting in the correct numbers. Mostly the coefficient numbers for temp. I’m looking to connect 5-200 watt panels to the new eco flo pro coming out. The only thing they say is max 1600 watts, 11-150volts/15 amps. I’m thinking I’ll be ok but still unsure. I’m in the south Denver area. I put -10 degree f for coldest at daylight to be conservative

You are a Bloody Legend Mate! Thanks so much! Your videos are Great!

Thanks really helpful. What about if they are wired in parallel?

Excellent video! Thank you very much for the great info.

What a legend 100% what I was looking for AND a brilliant free calculator :) thank you bud

So, these should be awesome on the prairies where it's cold, but sunny in winter?

Thanks mate! An awesome resource you are.

you calculator is fantastic ! THANK YOU !

Thanks for all your input, They are quite helpful ..

Thanks for making the video.

Great videos! I have a small Airstream with 1 90W Zamp solar panel. I plan to add 2-100W Renogy (pre-wired parallel) panels and have an external port for portable panels. I have 6-100W 24V Lion Energy panels that daisychain together in parallel. I would probably only use 1 or 2 of the portable panels. My question is can I get by with 1 mppt or should I use 2? I have a Victron 100/30 to install, however should I use a 100/50?

Hi great video. I have 140w single panel but might add more later. Can I use a MPPT that is bigger than I currently require so it’s good to go if I add more solar later?

Haha you caught yourself out when you where doing the editing! Awesome vidz👍👍👍

Great video and thanks for the calculator!!!

The calculator is awesome!

You created an excellent little tool, thanks for sharing.

Majorly excellent... thanks again, Nate, maaaaaate!!

thanks for the info, but for total amp calculation, I suppose it refers to 5 panels connected in parallel? As current of panel suppose to be the same if they are connected in series.

Can I plug the flux capacitor directly into the orgonne generator or do I need to modulate the carrier wave output with a cascading field zener diode?

thanks for the video, i'm buy the 150/35

can I have the reference of the equations used in this video? Thanks really need it in present time. EXPLORIST life - DIY Campers

Wow sharp fast direct information. Thanks.

Great stuff, and thanks for the calculator. With a 250/100 in the my setup, I’m apparently as cool as I can be. 😊 Your work is much appreciated!

Thank you for being a helpful good dude ✌🏽

You are so good young man,I have been going through all of your videos,I looking for one about inverters ,because I looking for a kind of inverter where I can get a neutral line and live line,thank you

OOOH my goodness.... even google translate could not translate that load of bobldie-gook you spouted in the first minute......🤣. Great video. I am a new subscriber and I am finding these videos so useful for our Narrowboat buid. Thank you.

Great video Nate. Much appreciated. Hey on a related questions have you done any videos or a post on comparing the very expensive solar panels (eg:Gioco GSP ) to the newer on the market and much more reasonably priced models (eg: renogy 170 mono). With our installation it will only actually be outside for 1 month a year and I am having a hard time justifying the 2-3x price on durability alone. A local dealer is pushing me towards the more expense of the two, so curious to try to figure out why. Feel free to point me to anything you have pre-existing, or you have found out there that you like.

Thank you for the video.

Nate- that's HUGE!!! The price of peace of mind is priceless. I don't mind doing the background work (using your calculator, doing some hand math, etc..), but- would feel 1,000 times BETTER if I could convince you to eyeball my work. Additionally, I will reference all of your work for determining wire size, but- as long as we talking solar- maybe, I could convince you to check that as well? I'd rather do this work RIGHT once, and, get years of service from this expensive equipment, than burn out controllers, ruin batteries or burn down my truck camper! Yikes!

next time you are in the london ontario canada i would let you hook up my victron energy system which is sitting in the corner great video like usual keep up the good work

BEST! Thank you !

Thank you for so much information. How do I get the following: 1) Temperature coefficient VOC and 2) Temperature coefficient of PMAX if this is not listed on my panel or my specifications sheet? Any help you can offer is rally appreciated.

Great info thanks, Question, I have 4 sunpower 170 flex panels 2 series 2 parallel, 4 battleborn batteries in parallel for 12 volt 400 amp hour bank, which of the Victron charge controllers would you recommend so that I can build up the system as well?

That’s great thanks. My question is, should I go up to above my ampage for the controller- my ampage works out at 52. Should I get a 60, or a 50 amp size controller? Thank you

That's great. Thank you!

This was awesome!

Hi i like the way you broke down the calculations and made it so simple i'm not that good with maths either but you my friend by far out shine a lot you should play the lotto with your skills after all its a math problem

Many thanks for this, and more especially to all the work you've put into the calculator which I have been using for the last couple of hours. If you have time for a question for folks who live in the tropics, here goes! I crunched the numbers for low temp (10C,) 25C (STC?), and 40C using your low temp adjuster. I could well be misusing its design function, but my voltages kept rising with temp. I was lead to believe efficiencies go down somewhere above 25C, it's usually above 35C in these parts, how do you size MPPTs for hot climates? Thanks!

Super useful information, I did not think about cold boosting my amps, You got my Sub and like

Thanks for teaching me

I will probably not watch another video because I got everything I needed from this brilliant video, you just deserve a sub anyway. Top content lad

Hay Nate: Trying to wrap my head around all the great material in your videos. Just not sure how to get them in order, maybe a number by each would help or where to start with number 1. I just tried your calculator and have a suggestion, which may be answered in a video I have not yet seen, which is to provide an estimate of the time it would take using the wattage/amperage calculations to charge a battery bank given say 4.5 hours of sunshine and the number of batteries in the array. In my case I would enter 3 batteries, 100ah, AGM. I think in the end that is what the crucial point is here, what is needed to charge a battery bank.

Thank you for the video

Not gona lie, my brain hurt for a bit there but came away knowing more. Great tutorial and will defiantly watch that again 👍

Hi, great vid Can I use 2 different panels that produce different amps and watts in parallel. Cheers

Great video!

Amazing website to help with calculations and visualisation 👌⚡✨

Love the videos. Always very good information. But, what if the panels label don't have all that information printed on it? Like the temperature info you mentioned. I bought 6, 200 watt HiTech mono panels. This confuses me on what size controller I should get. Maybe one bigger or 2 smaller? I have a class a motorhome (50amp) to power. I tried using your calculator, but couldn't fill in all the blanks. Any suggestions would sure be appreciated!

Yo the calculator is top tier! very good job

Hi Nate, your video are super easy to follow and your are excellent instructor - thank you! Question, how does the Victron Smart MPPT charge controller work in a solar - RV battery system? For example, I using a Victron MPPT 150/100 with 4X 200W of 20 Voc solar panels (800W, total Voc of 80V), plus a 12V 200Ah (2.4kWh) with the charging voltage of 14.4V ==> does the Victron automatically keeps the charging voltage at 14.4V and have the charging current at 800W/14.4V = 55.6A? Or is the system charging current = 200W / 20Voc = 10A? Can the Victron MPPT be program for specific charging current such as 50A? If the Victron MPPT charge controller can be set to 50 A, then what is the system charging voltage? I want to assess if my system operates with the limits of this Victron MPPT charge controller of 150V/100A. Thanks!

I love this! Been with ya since the beginning

Thanks for the info you pump out. I've been looking for a central source for related info and I'm glad I stumbled upon your channel. The amount of info on the vids you produce just flies above my head at initial screening but I slowly get the picture as I re-watch the videos. Question for you, though I'm not sure if this is within the scope of your channel or your website: would you have inputs as to how to integrate a solar charging system with the van's own charging system so the van charging system can help charge the solar batteries? Best regards from Ontario.

The first 30 seconds is exactly what I thought.

Hi Nate!! Still loving all your videos but not getting my head right around it yet! My panels dont seem to have all the info on them im running 2x 300ah 12v lithium batteries in parallel for 12v 600ah, I then have 2x 300w solar panels with open circuit voltage of 24V and max power current of 15A. I just purchased the renogy 50A dc2dc charger with solar input which has a max solar input of 660W and 25V. Im unsure on how to safely wire these panels in to get the most efficiency or if maybe i need more solar and a different charger/controller to efficiently charge my 600ah battery bank.. also not sure if that makes sense or if im just really confused haha

extremely useful video and tools! I do have a question though, according to your calculator we need an output charging current of 60A for our system, but how does this relate to the charging rate of the batteries?

Omg ur a wealth of knowledge thx for all your maths plugged my panel info into calc but it didn’t give a recommendation

Great video, and thanks for the help. I have one question. I am going to use two HQST 50w and two HQST 100w panels due to space constraints. I can’t figure out the math or how to enter the differing info into your calculator. I’m thinking the Victron 100 | 30 would be good but I wanted to be sure.

Hello, great video, really well explained. But I have a question, not sure how to go with my setup. I'm planning to run 200-300ah 12v batteries. My solar will most likely be 2x320w solar panels. They each have 43 voc, so I will probably series connect them to get 86 volts. So 640w panels at 86 volts will push around 8amps into the controller. My question is, how do I konw at what volts will the controller be charging the battery? 14.4 always? I need to know in order to size the controller. I think a 100/50 victron will do the job. If the controller charges the battery at 14.4 volts, 640/14.4 = 44.4 amps, which is below 50. But if the voltage charge drops, I will go over 50amps, over the controller max..Am I getting this right? Thanks all that help!

One more comment- Thank you for the great videos and detailed information!!

I am so grateful you choose not to talk so fast. There is another person who teaches about solar who does speak fast, while he has good content, his fast speech makes it difficult for me to keep up. I found your videos for the first time today. Thank you for speaking slower. If been studying solar God 4 months now and did not know I can use 24v pannels on a 12 system providing I don't go above the voltage threshold of my charge control. Ty 4 that 2 :-)

For the calculator features can you make it work for degrees Celsius too... Awesome vids. Keep it up.

Your approach to simplicity when dealing with complex issues is commendable. I have engaged with your calculator which calculates as designed, however, the Victron recommendation section at the very top doesn't seem to be recommending. Fact is it doesn't display anything. Wondering if there is a message there or not. Said differently, if there is no recommended controller displayed, does that mean something is wrong with the calculation data or something else?

This is a great calculator. However, one thing to be aware of is that Victron charge controllers require a 5 volt difference between the voltage of the battery and the incoming voltage from the solar panels to turn on. For example, lets say your battery is at 12.4 volts, the incoming voltage must be 12.4 volts + 5 volts or 17.4 volts. This is important in selecting your panel. In my case, I was looking at setting up a single solar panel with charge controller to maintain my batteries while my RV is in storage. This is on a truck camper with limited space on the roof. I plan on an eventual expansion to 300 to 400 watts but initially I figured a 100 watt panel would be adequate to maintain my batteries. I bought the panel and a Victron 100/20 charge controller for future expansion. As it turns out the output voltage of the panel is only 16.77 volts. The charge controller will not turn until the battery voltage drops to11.77 volts. Not acceptable in my opinion. There are lot of panels on the market with higher output voltages and this wouldn't have been an issue. My solution is to buy another panel and run in series to double the voltage output. The charge controller should work fine after that. Just be aware of the 5 volt requirement to turn on your Victron charge controller (not sure how this affects other brand charge controllers) when sizing and choosing your solar panels.