How to Size a Solar Charge Controller

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In this video, I tackle everything you need to know about how to size a charge controller, ensuring your solar system operates at peak efficiency. With over 2000 positive reviews, my book has powered up countless off-grid adventures, and now, I'm bringing that expertise directly to you.
Starting with the basics, we'll explore how to figure out what size charge controller you need, breaking down the calculations in an easy-to-understand format. Whether you're dealing with a single 12V battery and 200 watts of solar or scaling up to a more complex system, I've got you covered. From understanding the importance of series vs. parallel wiring to diving into the specifics of solar charge controller sizing, this video is packed with invaluable insights.
We'll also dive into real-world applications, demonstrating how these principles apply to actual setups like a cabin powered by solar. Plus, I'll share tips on optimizing your system for both safety and efficiency, including the critical considerations for fuse and wire sizing. And, for those curious about maximizing their system's potential, we'll discuss the maximum input voltage your charge controller can handle and the impact of your wiring choices.
This video is not just about theory; it's about practical, actionable advice. Whether you're wondering 'what size charge controller do I need?' or looking to refine your existing solar setup, you'll find answers here. And I'm eager to hear from you too - leave a comment with your setup or any questions. Your insights make our solar community better.
For a deeper dive into building a resilient and efficient solar power system, check out my book, 'Off-Grid Solar Power Simplified.'
00:00 Introduction
00:25 Influence of battery voltage
01:27 Calculating Charge Controller
02:57 Maximum input voltage
03:48 Max input voltage Calculation
05:04 Fuse and wire size
06:17 Cabin Calculation example

[@cleversolarpower]

My book on Amazon: cleversolarpower.com/off-grid-solar-power-simplified 7 Free off-grid solar diagrams: cleversolarpower.com/free-diagrams/

[@RichardByrd-my3vs]

Sir, you do a fine job of clearly explaining solar power. Best I've seen to date. Thank you!

[@ktm640]

An excellent informative to the point guild that most people will need. Thanks very much.

[@Ekanselter]

Excellent as always. Very good presentation.

[@cleversolarpower]

Glad you liked it!

[@richardcurrin7812]

This is the 3rd or 4th video from your channel I’ve watched as I just recently found it and subscribed I paused the video long enough to go to Amazon to order the book Your videos are excellent!

[@cleversolarpower]

Thank you Richard! If you have questions, feel free to email me.

[@comep9702022]

Many thanks for this very informational video!

[@cleversolarpower]

Glad you liked it!

[@frankseda1]

Great information. I have a Li Time 60A charge controller . I am using 4 100w panels. I am planning to add 2 more panels. Total 600 w. Equal 42A. Easy to understand now. Thank you very much.

[@xe-xx8vu]

I have 6 BougeRV 200W 12V 9BB Mono Solar Panel + 2 100W HarborFreight panels I wired everything in series to charge a Bluetti AC300 + 1 extra battery I get 1.0kW on a nice sunny day but eventually I want to setup something with a charge controller to power other things and was wondering what's the right side charge controller to get. great videos thank you.

[@user-pp6tw8ez3f]

Thank You for the instructional videos 🥀🥀🥀🥀🥀🥀🥀🥀

[@musicrecordstudio]

I'm truly enjoying your videos, so informative. I have (6) 450w solar panels, can I run them in series using an MPPT 150/70, a 48v 3000VA Multiplus and a 48v 100Ah LiFe P04 battery?

[@gregjacobson2687]

So glad I found your channel. I am trying to figure out what i need to set up a solar panel(s) to keep my boat battery charged. Currently running a 36V 60AH LiPo battery for my trolling motor. Trying to figure out what i can use as the boat is on a storage lot so not much room for big solar panels.

[@cleversolarpower]

Welcome aboard! You need to wire panels in series to go over the minimum recommended input voltage to charge a 36V battery. For example 3x 50W solar panels in series will give you 18Vx3=54V. This is enough to charge the 36V battery with an mppt. 2 18V panels will not be enough.

[@gregjacobson2687]

@@cleversolarpower thank you for the reply. That makes sense sort of lol. Not sure if I will be able to have 350 W panels due to space. What do you think about the MPT boost controllers? Looking at a 100 W 12 V panel with the boost controller to charge, the 36 V battery.

[@heroesandzeros7802]

I have multiple PV arrays around the house, garage, and at my business, 12V and 24V systems. I usually use the 30A Eco-Worthy charge controllers rated for 750W. The max output of the smaller PVs is 41.666A but the charge controller never gets anywhere close to that. The most I have ever seen is about 21A and that does not last long. I also have a 2250W 24V array (3 sets of 3 in parallel with separate feed wires) on 8- 12V lead-acid batteries. I use 3- 30A charge controllers in parallel. The highest amperage I have seen is about 6A from each charge controller. The only loads that I have is an alarm system, a 16 Camera DVR, and a few LED light Bulbs. This load does not even scratch the batteries.

[@boothleg3052]

hi have a 30a charge control what panel should hi use

[@jasonjaffray4025]

PERFECT 🥇

[@ChrisKobe]

Hi Nick! Love your videos and just got your book. I am building a 48v system for off grid storage container. I have 100Ah 48v (Li Time). I was hoping to use a 100/20 MPPT Victron I was given to charge it with. I don’t have any panels yet. I get the input voltage limit of CC but can I exceed CC 20 amp charge spec by adding parallel strings?

[@cleversolarpower]

Thanks for getting the book! Yes, you can add more panels. You will just lose some power because of the over-paneling.

[@AbcDef-ej1fd]

I have one solar panel of 555w and one 100AH battery so how many ampare of MPPT charge controller i required?

[@user-ve8ey7cv1v]

Thank you for the video, it was quite informative and engaging. I however have a question, combining the panels in series increases the panel voltage to 48v, which of course can be handled by the MPPT SCC but shouldn't the connected battery be a 48v battery too?

[@cleversolarpower]

No, the mppt can always step down the voltage. With an mppt, the current automatically increases. A pwm doesn't increase the current, just cuts the voltage. So a 150voc solar panel string can charge a 12V battery.

[@chukwuemekaejekwu6870]

Please I need an advice I have a solar two panel 190 Watt and one 200 hands battery 30 amp charger controller 6 gauge wire with 1.5 ups

[@carlharmon9590]

Thank You for the instructional videos I have 2 230AH battery's collected in parallel so 460AH of battery With A Victron 150/70 Charge controller use A 90Amp breaker and 4 Ga Wire on controller? and 5 100watt Panels connected in series? Does this seem right?

[@cleversolarpower]

Seems good to me 👍

[@benfournier290]

Hello, I'm building a portable 24volt system with 2 small sized 12 volt 100amp Lifepo4 batteries. I have one 200 watts pannel and I ordered the 100/20 and think I would be able to upgrade the solar an other 380 watts. it this correct? I also have a 24 volt 3000 watts inverterI and converted 24v to 12v I'm open to recommendations.

[@eliudmuriigi]

I have 2 batteries 12v, will I add the 12+12=24 divide by the wattage of my panel or I'll just use 12v?

[@panospapadimitriou3498]

2x 100.20 and a 150.35 for future bigger panels .. for 48v and up to 60% of their power!!! i want to see when instal the capability in shade and different angles setups

[@user-qy9py8ip3y]

Great video can i ask for some advice i have a 1000 watt inverter a 10 amp charge controller with one 110 watt solar panel on a 12v system on my RV i would like to up size to two 200 watt panels upgrade to lithium battery and 100/30 charge controller what do you think would be best thankyou

[@cleversolarpower]

Keep the existing 110W solar panel on the 10A charge controller. Add the two 200W solar panels in series with the new charge controller. Two charge controllers on one battery is ok. 400W/14.6V=27.4A -> 30A is ok.

[@IsmaelKonare-by9iq]

In your calculation of the charge controller capacity you used maximum power at STC of the panel instead of Max input Voltage. I'm confused. Please can you clarify?

[@cameronrudibaugh2247]

Hello! Thank you for the video! It was quite helpful but I was wondering if you could offer some advice with a new solar setup. Another person was working on this project for a non-profit but they couldn't finish the work so I'm stepping in to help out. They ordered three 350W (40.7 VOC) solar panels to run on a 100W/20A charge controller with a 12V battery. Based on your video, the charge controller would be highly inefficient. What size charge controller would you recommend for these panels?

[@cleversolarpower]

350W*3panels=1050W/14.4V=73A charge controller. You can still use the 20A charge controller, but you can only get 20A out of it. You can get two more of these charge controllers and have three of them in parallel. However, that is not the best solution. You need a 150V input and 70A charge current charge controller. Victron has one.

[@cameronrudibaugh2247]

Fantastic! I had done my research and this corroboration was elucidating. I feel confident communicating with the organization about what the necessary next steps are. Thank you for being a a great solar community resource!

[@zzzdoerrr2826]

Hello. Thank you verry much. It's really helpfull! Is it possible to use victron mppt as a booster. For exemple i have a ebike with a batterie 48v. 25 amp. And a solar panel 100w 12 v ? I want to charge my bike while riding... let's say with a smal victron mppt. Have a nice day!

[@cleversolarpower]

I'm not sure what you mean by booster. The input of the mppt needs to be 5V higher than that of the battery. You can use a step up DC to DC converter and then feed it into the mppt.

[@zzzdoerrr2826]

@@cleversolarpower Thank you !

[@dizawnofwizar]

Do you have to consider output power? IE you have a 100w panel charging a small battery, and once or twice a day you have a highish amp draw pulling power for 5 minutes and then shutting off - do you have to size your controller to allow for that draw as well? Or for something high draw you just connect it directly to the battery?

[@cleversolarpower]

The charging and discharging are completely separate. You must wire your loads directly from the battery or busbar. A charge controller doesn't have an influence on the load.

[@ondekiddancer25]

my solar panel ratings is 30wtts,12v

[@nkosenhlekumalo4]

Please for give me if im out off track i want to make a very small 24v system with a 60a PWM I would like to find out if it porsable to use a 60amp charge controler to charge two 12v 7amp connected in series

[@cleversolarpower]

Check my video about C rate for more information.

[@deanfinkel3381]

Awesome video, just to clarify I could you a 290 watt 32 volt panel with a 30amp solar controller to a 12 volt system ? @cleversolarpower

[@cleversolarpower]

290W/14.4V=20A. A 30A charge controller is ok.

[@masudsaleh5155]

3:00 MAX input voltage ⚡️ 👌

[@Retired..Mostly]

I’m currently sizing my 24volt rv solar setup. I’m planning on installing 1250 or maybe 1500watts of solar (5x250 or 6x250). If I’ve do the math correctly I’m going to go with a 150/70 charge controller to cover either setup. The charger’s maxPV is 150 and the panels VOC is 22.8. I could go with 150/60 controller however it would not allow for any expansion to 1500 watts. Your thoughts please.

[@cleversolarpower]

You should only have a maximum of 5 panels in series. 22.8Vox*5*1.25=142V. You can get a 150/45A charge controller as well. 1250W/28.8V=43A

[@soleespena6622]

So if your having a 20amps mppt and allows only 60volts voc it will be exempted if you turn your battery to 24volts system?

[@cleversolarpower]

I don't quite understand your question. But you can add up to 60V of solar panels, if the mppt is compatible with a 24V battery and the solar voltage is higher than the battery voltage +5V, then its ok.

[@adebayoogunsade369]

I have a lithium battery 200ah and 2X 180 watt panel what’s the right pwm amps charge controller to use????

[@cleversolarpower]

Put your panels in parallel. 180W*2=360W/13.6=26.5A -> 30A PWM.

[@burlystone9655]

Got 4nos. Of 12v 165w panels , 150ah batt., 60A pwm charge controller but its getting super hot in the back of charger

[@adamsisernik4556]

Hi, can you pls tell me some info? Since we will be charging the 51.2V 230ah 11.7KWh Wall&Floor-mounted LiFePO4 Battery (link bellow) with 3 x 480W solar panels ( Vmp = 37.10, lmp = 12.95A ), we would like to have information on which Victron MPPT controller is suitable so that the battery will be charged properly (Operatin value charge of the battery is 43V - 58V). Does the Victron 150/35 match the charging voltage? Which fuse must I get? Can such a battery be simultaneously charged from the panels and at the same time transmit energy to other consumers?

[@cleversolarpower]

I need to know your Voc, i will take a guess and assume it's 45V. 45Voc*3panels in series*1.25=168V -> you can only use 2 panels in series. 480W*3panels=1440W/57.6V=25A. You can get another panel and wire the panels in a 2S2P configuration. 1920W/57.6V=33.3A Then you can get the victron 150/35A

[@alitomix]

Great video, but now I'm a bit confuse, this video is about battery + controller... and you got another about battery + inversor..... can you make one with the complete setup? battery + controller + inversor

[@cleversolarpower]

These topics are completely different, that's why there are two videos. Follow them and you will get the answer.

[@OYMInternetRadio]

Hi, a bit of confusion regarding the figures. If I have 2 x 130w panels and I have a 24v battery setup with a 12/24 charge controller, does that mean that I divide 230w / 28.8 to get 7.98amps, so I need a 10amp charge controller? As the panels don't come in 12/24 version, how does the system know?

[@cleversolarpower]

260W/28.8=9A -> 10A charge controller. The charge controller sees the battery voltage. If the voltage on it's terminals is closer to 12V, then it detects a 12V battery. If it's closer to 24V, then it detects a 24V battery.

[@s.karthick1474]

sir can i use the USB output for ardino uno power supply

[@cleversolarpower]

You will have to check the current rating of the USB output in the manual.

[@bosedeosanemo458]

Please can you help me i want to use a 3200w panel (400 x 8) with a 24v system with a 100amps solar charger... how do i configure it ?

[@cleversolarpower]

It depends on the maximum input voltage of your charge controller. And you will have to wire in a hybrid connection. This depends on the Voc of your panel.

[@anilbhargava9310]

Hi can you tell me if this set up will work…? I have an EcoFlow RIVER 2 Pro Portable Power Station which states “Solar Input: 11-50V, 13A, 220W Max” I also have the following solar panel “VTOMAN VS400 Portable Solar Panel 400W 40V, 23% Efficiency Foldable Solar Panel” Question is, will,the two be compatible? The Ecoflow states 220W MAX but according to your calcs (400w / 40v = 10amps ) so (seems ok?) Am I missing something? Not sure why 220W is a max… If not compatible could I use an MPPT controller to lower the panels voltage ? Thanks

[@cleversolarpower]

The max input is 50V. Take your Voc and multiply by 1.25, this should be max 50V. Not sure why they say 220W max. 13A*50V=650W.

[@bmack2076]

The Question I have has to do with the Max Power (STC) rating of a Solar Panel... say 200 watts, which is the basis for the calculations. If the panels are mounted 'flat' on the roof of an RV with maximum power generated would be less, correct?

[@cleversolarpower]

Yes, you have to angle them so they are 90° angled towards the sun.

[@bmack2076]

In theory "flat" panel installation would reduce the input power to the Charge controller, lessening the concern if the rating of the controller is "borderline"... Correct? @@cleversolarpower

[@senogamoses5319]

Can a Safety Factor of 0.9 be used for victron charge controllers when determining max number of panels to put in series ?. I think this is what is recommended by victron.

[@stevenjohn350]

from the video I gathered that the smaller the Safety Factor used, will result in a smaller life span of the charge controller, because it runs HOT all the time. Hope that helps.

[@senogamoses5319]

​@@stevenjohn350 You could be right

[@koalafan1576]

Are we allowed to put too high of a charge controller? For example if I have 200w solar for 12V batt so we require a 20a charger, can we use a 30a charger in case later we buy more solar panels?

[@cleversolarpower]

Yes, no problem.

[@hollygrinstead7252]

​​@@cleversolarpower@cleversolarpower Hey how about 170w panel with 1x 110amh agm leisure battery. Is a 40a charge controller too much? The type i would like to buy is only available in 20a and 40a. I want to be able to buy more panels and batteries in future

[@byronsowntime]

maybe a silly question.. I have 2 panels of 540 watts each and voc is 50. I have a 100v to 30a charge controller from victron..what combination should use? series or parallel or can i use it at all?

[@cleversolarpower]

You should wire in parallel.

[@byronsowntime]

@@cleversolarpowerthanks ...ill hit your sub right now

[@Ridershani530]

Sir i have 180w 2 panels and battery of 70ah with 30a pwm charge controller.is this okay or i have to install mppt

[@cleversolarpower]

If you wire the panels in parallel then it's ok. Check my video about pwm vs mppt.

[@Ridershani530]

@@cleversolarpower I saw that video sir is it okay to install 60amp 0r 65 amp mppt with my system

[@Ridershani530]

Loadshedding 3 hours in morning 3 hours in evening 3 hours at nights..my output load is 2 ac dc ceiling fans

[@TOMVUTHEPIMP]

Is that a 12v Lithium? AGM? Lead acid??

[@TOMVUTHEPIMP]

On a boat. Lots of shading. How about parallel example too?

[@covecarpentry]

Ive got 400w solar in my 12v system with a 30a mppt charge controller, its only ~ +10% safety margin but i think that's ok. Do you agree?

[@cleversolarpower]

You will miss out on bright cold days, but that's ok.

[@covecarpentry]

I see now victron makes a 150/35 that would be perfect.... my wife was right! Thanks again Nick.

[@user-ky1pe2jt5b]

I have two batteries 100AH each. Can i connect them in parallel and use a 40A charge controller with two solar panels of 200watts each?

[@cleversolarpower]

Yes, paralleling the batteries will give you 12V. Wire the panels in series to reduce voltage drop if you use an mppt.

[@user-ky1pe2jt5b]

@@cleversolarpower Thanks. I appreciate. So I can use my 40A charge controller and my 2000watts inverter?

[@melak2443]

It is a Great explanation like it so much,God bless you.

[@abyidicula2009]

Hi I just want to start 100 w panel with 100 ah battery is that okey to use 75/15 mppt charge controler ?

[@user-ej6qr9xz8n]

What is better? Fuse or solar circuit breaker?

[@cleversolarpower]

Fuse to protect individual series strings and one breaker right before the charge controller as a disconnect switch.

[@CollinBaillie]

I think the only thing you missed, was a consideration of what is a safe charging current for your battery (bank or pack) If you have a single 75aH AGM battery, you don't want to be charging with more than about 15a. For a LiFePo4, you'd probably want to charge at no more than 40a. Otherwise a great video!

[@cleversolarpower]

Good point 👍 I have touched on this in my video about C-rate.

[@user-hy3qe5jo7q]

Hey I have a MPPT 100A charge controller, combined with a 12V deep cycle battery, I'll just be running a LED and security camera, what wattage solar panel you think I would need?

[@cleversolarpower]

Checkout my video about sizing a solar power system. I explain in detail what you need.

[@icantok4285]

The question is How if the landlord leave their home and there is no home's load used while landlords leave their home at all and all batteries is fully charged? Where does the solar panel energy will go or delivered when a daylight time and solar panel within produce the energy condition? Anyone can help to explained to me please?

[@cleversolarpower]

When the battery is full the charge controller stops the electricity flow. Just like your light switch does at home.

[@1GREATDANE]

1600 Renogy Solar Panels and dua Renogy 60amp MPPT Charge Controllers and dual Battery Banks 4 RENOGY 200amp AGM 2 CHINS 280AMP Lithium Iron Phosphate 24 Volt WZRELB 2500 watt Inverter

[@cleversolarpower]

8 solar panels go to the AGM battery and 8 to the lithium battery?

[@CollinBaillie]

But what to do with the other 1584 panels? 😝

[@1GREATDANE]

Yes

[@1GREATDANE]

*100 Amp RENOGY SOLAR PANELS for 16 Total, My Thought was Back Up Battery Bank Management here...

[@cleversolarpower]

@@1GREATDANE You can switch the inverter from one battery bank to the other manually?

[@JcCramer-ob4vd]

Can you send me some signed? Better some print ouch absolute connection to my Bixby set alarm for and connect solo panels togetperiod. Thank you, babe would be appreciated.

[@markfoster5240]

I’m still baffled. So many people give different answers. I have a 50amp Renogy DC to DC and Battery charger. I bought it because it says 660watt max solar. I have 440 watts. However I didn’t think of watts. The solar says max VOC 52.2 the Renogy says Max Voltage input 25 volts……Everyone is saying it won’t work. Help

[@cleversolarpower]

A DC to DC battery charger is different from a charge controller.

[@markfoster5240]

It's a charge controller too.

[@markfoster5240]

Renogy dual input DC to DC on board battery charger with mppt. Its actually a 50v max Solar input. It also has overvoltage protection. My panel is 52.2 max volts output.

[@tpkashif]

Please share calculation for 3000 watt With VOC= 51 and battery banks for 24V & 48V solutions

[@cleversolarpower]

You can repeat the calculations in the video with your numbers. Easy 😉

[@JohnBraman413]

point of reference is whatever your battery bank size, double on the solar panels. 400ah of battery, use 800watts of solar. don't remember if it was will prowse that mentioned that on his youtube channel.

[@cleversolarpower]

Doesn't work if you have a 24 or 48V battery, you will be seriously under sizing your panels. I made a video about how to size an off grid solar system. Go give it a watch 👍

[@fredericg1842]

Hi, A 200w solarpanel will never deliver 200W. May be 160-180 at midday if it’s new. The voltage you use to charge your batery depends on the type of your batery. A panel will deliver its maximum power only few hour a day. So your installation. That’s why you can size your MPPT at the minimum, i mean if you need 50A you can buy a 50a because it will work at his maximum only 1 or 2 hours a day if no clouds, no shadow, … If people have doubt, they can use Victron tools to size their MPPT, it’s friendly user. Regards

[@cleversolarpower]

A 200W panel can deliver more than 200W on a cold sunny day. Doesn't happen much, but it is possible. Yes, the charging voltage depends on the battery type. Yes, a panel wil deliver it's max power over a few hours, so why not capture all of it? I do agree, but using an extra margin is not bad, especially for the max input voltage. Power depends on the individual preferences. This is just how i do it.