Solar String Voltage Made Easy! How many solar panels can you safely connect?

[@WillProwse]

0:00 Intro 1:16 What You Need 2:37 Calculate Minimum String Voltage 5:04 Calculate Maximum String Voltage 6:18 Temp Coef Calculation For Cold Climates 10:06 Solar Generator Calculation 12:48 Current Calculation and Conclusion Parallel String Video: kzbin.info/www/bejne/eV7OYYp-f5mFrrMsi=ALnTndizN34Y4kk7 Lowest Temp Solar Map: energyresearch.ucf.edu/solar-certification/solar-reference-map/ Temp Coef Equation: www.greentechrenewables.com/article/solar-inverter-string-design-calculations My 12V Solar Book for Beginners: amzn.to/2Aj4dX4 Diy Solar Forum: www.diysolarforum.com

[@mochouinard]

I feel like this more apply to initial installation. Or if you disconnect and reconnect. Once connected to your system, will it really generate 48.5volt at -17 at night for example ? That said, why take the chance someone turn on and off an safety switch at -17oC :)

[@dyslectische]

Will We have a discussion about a mppt. What happens if you mppt can do 300watt input . And we connect 600watts on it . What do the systeem with the rest ? I tell we have ampère spikes and can damage the mppt over time . I like to see a test with amp/watt meter between the solar and mppt to see what it will do and if the ampère spikes Thanks

[@WillProwse]

@@dyslectische if you don't exceed the voltage limit, it should be fine. It will just regulate to max current and hold it there. If it's in hot environment and running at max output for years, will fail sooner but should be fine

[@wademyers6051]

Great video Will. Excellent information 👌

[@dyslectische]

@@WillProwse thanks

[@AdamDavisEE]

I appreciate you spending time on the cold temperature issue. A lot of 150v charge controller's are damaged in the north because people follow the simple rule, but don't understand the cold weather issue.

[@ReinhardSchuster]

150 V which toys are you using over there? My 48 volt battery system is charged by a Deye 12 kW which can handle 1000 volts on every string.

[@Teknopottu]

​@@ReinhardSchusterNice system you must have. Not everyone has need or resources for such setup so most systems are small 12V stuff with few panels.

[@AdamDavisEE]

​@@ReinhardSchuster If you point me to 600v+ 5kw MPPT charge controllers that are under $150 each I'll start buying those instead of the $100 5kw 150v mppt charge controllers I'm currently using.

[@pin65371]

My only question is with the low angle of the sun would you actually be hitting the full voltage even in the cold?

[@Pobee]

@@pin65371 Likely not. You can tell from WIll's face.. he has burned up a few of them.. It's expensive, and scary actually. Hopefully you installed in a location where you could have a barbeque.

[@pgiatrakis]

Over the years, I’ve used your advice for solar and batteries and I really appreciate all your help. Your information is priceless and you have saved me thousands of dollars thanks again for your channel and all your hard work.❤

[@guywhitman1854]

What a Blessing you are to the Solar first timers. This video probably saved me hundreds in damage if not more. I Pray GOD continuously Blesses you and all Brothers & Sisters in CHRIST JESUS.

[@WillProwse]

Hey thank you!!! 😁 Glad I can help!!!

[@elitearbor]

In your example, where I live, the maximum potential VOC would be 52.2! That was an eye opener, thank you wholeheartedly for this video. You've saved me from making an extremely costly mistake.

[@thinde88]

Just got my pallet of Aptos 370w panels delivered today. I’m so happy Signature Solar decided to go with FedEx for shipping. They came in perfect condition for the first time I’ve order panels.

[@angloblaxon]

I just installed mine on a wooden cover. Love the look, price, and wire lengths.

[@mondavou9408]

I just ordered the minimum 10. Was that what you ordered? I'm hoping that size is a well packaged "unit". Signature Solar tells you to order more panels than you need because of expected damage in transit. I hope I have a shipping experience similar to yours!

[@angloblaxon]

@mondavou9408 I ordered 20. It came on a pallet that I placed on my driveway. It was very well packaged and I installed 16 so far. None were damaged

[@timsteinkamp2245]

I had just gotten a pallet of 10 panels. I was opening the two per box panels inspecting them and setting them around. Just before I was done with the cardboard unpacking a wind came up and picked a panel up into the air and dropped it into another panel and put a hole into the glass of another panel and shattered the glass. It could still work with repair but I figured out during installation I needed 3 panels of three for my system so the tenth panel was a spare. At the time they were $1800 for poly panels. Delivery was $300 of the 1800. It's been almost ten years and I still have all those panels.

[@repuSgnikcuf]

I was literally doing these calculations today, I am moments away on getting 16 of the exact 370w panels you calculated for (when hopefully they come back in stock, to hook up two 8 panel stings to a 6000xp. Hoping to run my water pump and my refer's and freezer's, and starlink and server, pellet stove off grid permanently. Thanks for all you do, giving people like me the confidence to do this on our own.

[@wmfoster]

If you have the mounting space for it, your inverter will be more productive with another panel (cold zone) or 2 to 3 panels (temperate zone) per string. In Australia most systems are installed with panels sized to 1.33x the DC rating of the inverter.

[@repuSgnikcuf]

@@wmfoster i am at the 45th parallel, The 6k eg4 is overkill for what my main goal is. But i would like 240v for my 3/4hp water pump (pumps from a 3000 gal tank, gravity fed spring) @ 120v they only last a few years. And since i was going with the 6000xp i might as well bump up everything to offload a few more circuits to it. Original goal was about a 3.5k to 4k solar and 3k inverter but I haven't seen any with 240v for much cheaper than the 6000xp.

[@repuSgnikcuf]

45th NORTH parallel, I should clarify since you are south of the equator :-)

[@mondavou9408]

My brother! Same. My pellet stove is a big pig: 325 watts whenever its on. Going to add a cheap wood stove (pellets keep going up, and aren't always available) so I have a non electric option that isn't gas.

[@timsteinkamp2245]

@@repuSgnikcuf Isn't the South 135?

[@scmattson]

I ordered your book back in 2019, built a great 12volt system for my cargo trailer, now we are moving up to a travel trailer and looking forward to getting into 48volt - thanks, I continue to learn something new each time I watch your videos

[@timothytrueblood5939]

Professor Will, your talent in presenting this technical subject matter is stunningly brilliant! And, entertaining! I’m 75 yo, and you make learn this new subject area fun, for me. Keep up the good work, Mate.

[@knight7866]

Good video. Gotta be careful with 4 panels with DFP. At 150 in normal conditions it would leave no room for increased voltage in cold weather. Best setup for delta pro is really 3s2p. Delta pro can bring in 15.9 amps at max and it would help maximize input in days with clouds or rain.

[@aogulla]

Hi @WillProwse I think you used the wrong temperature reference at minute 7:24. The Voc at STC is measured at 25 deg C and not at the NOCT of 45 deg C. Therefore at -17 deg C, the maximum Voc will be 41.4+(-17-25)*(-0.28*41.4/100) = 46.27V i.e. an increase by a factor of 1.118. With this in mind, it should be possible to string together 10 pieces DNA-120-BF26-370W modules (10s1p) with a combined Voc of 462.69V while leaving some 17.31V headroom just in case the temperature ever dropped to -32 deg C.

[@richardkent9621]

Just be careful when dealing with that high voltage DC. If it gets ahold of you that's probably it. I worry sometimes about people doing this without the understanding of how dangerous it can be. I don't want to scare anyone off, just THINK before you DO. Electricity doesn't make noise, doesn't smell, doesn't light up, just waiting for you to complete the circuit.

[@gratefultrucker7781]

Facts! 150 v dc should scare the piss out of you, if it doesn't, spark the wires together to gain a proper level of respect . Bzzzzzzzzzzb

[@bassam_salim]

In my country people work with live 240 volts AC ​@@gratefultrucker7781

[@RichardQuaid]

Spend a little extra time and money on grounding your system properly.

[@richardkent9621]

Grounding is great, but if you get between two different voltage potentials ( if you put your volt meter on the two points you would get a voltage) and the difference is great enough you get poked. Lots of factors involved, people have different resistance, is you skin wet or dry, is it going from you to ground then boots matter, if it is going from one hand to the other that is the most dangerous it has a high chance of going through your heart. It takes very little power to stop your heart around 100 milliamps. That's why GFCI's trip around 5 mA in about 1/10 of a second. If you grab a live wire with enough power, and it doesn't take much, you will not be able to let go. It doesn't blow a fuse, trip a circuit breaker or stop until something stops it. Should you be unlucky and get a bad poke but someone kills the power to save you, GO TO THE HOSPITAL it can mess up your blood and still kill you. Not likely with just a "snap ouch" but if you get stuck on a cable and someone or something gets you free the risk is greater. When working with solar, the higher the voltage the smaller the cables but the more dangerous it gets. Electricity takes the easiest path to get where it wants to go, DON'T BE THAT PATH.

[@mattman6199]

The more people play with power the more respect they get… all you can do is hope they get the respect fast enough to live through it …

[@rongray4118]

Will - I had a great conversation with a young man here in Reno about you yesterday. Your videos have assisted the both of us many times over. Blessings to you from Reno-Sparks, Nevada! Deanna and I are finally up on the mountaintop - off grid. Still working out the best solar array(s) for the mountaintop to maximize the SMA's and keep the 48v battery bank(s) up but we are managing so far. Happy Thanksgiving and thank you for all you do for the rest of us!!

[@herb7877]

Excellent material. I built my first little system after following you about 7 years ago We both have grown since then. A sincere thank you for sharing your knowledge.

[@WhatNowChris]

The video I’ve been waiting for. I need to add more panels.

[@bobwhat7629]

My 16 Aptos 370watt panels arrived today and I have the 6000xp after your review. Really appreciate seeing you validate my rough guestimate for the two solar strings.

[@johneaton3609]

On the 6000xp do you connect the entire string to PV1 or use 2 smaller strings and use PV1 and PV2? Thanks...

[@bobwhat7629]

​@johneaton3609 I finally got the conduit in the ground from pv to home. 4 wires for the 2 strings.

[@Tuggs]

The book is awesome used it when I got started building a system for my house.

[@allen35315]

You, sir, are a life saver. Here I am with my 1,600 watt max in the northeast thinking I can safely use 4 400 watt panels - too bad the manufacturers aren’t more straight forward with us newbies. Thanks again. I’m def subscribing

[@hicksonb]

Thanks great to get it so clear, now to get another 9 panels onto this inverter 👍

[@dr123hall]

Watching Will for year or so, especially today, Just saved my on the way system to ‘coal mine cold’ Kentucky! How valuable every single video. Plus, I reviewed the new purchase of elementary 12v mobile systems, “Mobile Solar Power”by Wm. Errol Prowse IV!

[@lenwhatever4187]

Very good. Great for a full sun location with lots of room. These are most of the people in your audience so that makes sense. Things are different on boats... and the same. they do take a lot more thought. 400 watt panels on a sailboat are generally not a good idea... though I see them often enough generally in 12 parallel configuration. I have found using two serial strings (or more) where each serial string has all of it's panels in the sun at the same time. Cut cell technology has given us one of two things: A) a normal sized panel with some shade compensation (though generally not in a way that makes sense on a boat) or B) Smaller panels such as a 100W panel that is less than 30inX30in. These small panels are more expensive than a 200watt 30x60 (ish) panel... but it means I have room for 24v (42voc) on each side of the boat rather than just 12v.(21VOC-ish). This is compared to most boat systems that end up even with 1000watt systems having a 12v(21voc) input to their MPPT controller .... which they have to oversize to get to the current rating. Unfortunately, while most portable refrigeration systems are 12/24, the navigation instrument manufactures have not got the same memo and so a 12v system on a small boat is still what we have. So the flat surface I have is 60inx60in but much of the time one half of that is shaded by the boom and sail. So I can't count on a 400 watt system but rather two 200watt systems of which I know at least one of them will be producing at any one time. Small panels are the thing for boats for best output... I would guess that having two mppt controllers would also pull more power out of the shaded side too but I have limited space for mounting such things. A lot of the small mppt controllers are the same size for different current ratings too, which doesn't help. However, 200watts is still pretty good for my needs. I can almost make do with the 75watts I get from the system on the boat when I bought it (350wats of 12v panels into a PWM charger) :P

[@s13ef9]

Thank you for another excellent video. Your channel has become my favorite by far for real and useful solar info.

[@patblack2291]

A concise and helpful video, thank you. I wonder if you would consider a video on overpaneling, since you have mentioned that you can do that in your context. I am in a cold weather zone and have been curious if I could do that too, but I don't know how to make calculations for that. For now I am sticking with the math as you described here, to be safe.

[@danmccauley6626]

I want to thank you for sharing your knowledge with others. Your videos are very helpful and super easy to learn from.

[@micklaws5520]

I have two strings of 420 watt panels, each string is a row of 7max in series than parallel for the current. Each string is roughly 350vdc at 20 Amps. I got a deal on 8 gauge solar cable so the runs are around 100 feet feeding my SolArk. I made darn sure to keep my act together and make darn sure to hook it all up at night etc, etc. Last thing I needed was to be a Charcoal briquette in the pasture, lol. Battery charging is seamless.

[@michaelbradley1636]

Thank you very much Will, for clearly explaining how to calculate the minimum panel voltage and maximum panel voltage for a series of panels depending on how much voltage your solar controller requires. It is EXTREMELY important to know. In fact, I do believe, from research on other solar charge controllers, that the maximum and minimum are VERY DEPENDANT ON THE VOLTAGE OF THE ATTACHED BATTERY. As an example, I have a string of 12V panels x 4 in series that output about 90V. (They are Ecoflow 100Watt bifacial panels, you can lookup the specs on the internet). One solar controller I've ordered is 12/24/36/48V auto-sensing. The specs state that if the battery is 24V, there is one (lower) min/max calculation, but in my case, with a 48V battery, the min. PV is 60V and the max. PV is 100V.

[@stewpeanut]

Will, with something like the Ecoflow DP, are you not as concerned with calculating the voltage at the colder temps b/c of the potential overhead built into those units? In your example it looks like you'd exceed the max voltage at your same -17c example.

[@AngelinaThumbelina8]

I can't comprehend anything you're saying but I love listening to your voice and I love when you make eye contact with the camera so I feel like you're looking into my eyes 😍

[@simonh2679]

Great clear instructions...really helpful to get people sorting stuff out themselves and having self reliance. Thanks

[@sierrabum6589]

Will, great explanation to a problem I wasn’t aware of! Using an EG4 3k all in one inverter on my cargo trailer I was focused on keeping my input DC

[@kurtmarkel628]

I never comment on videos. This is what I’ve been waiting for. I just ordered the aptos 370w panels. I am looking for the “ideal” inverter which doesn’t exist, so I’m trying to configure my panels to find the best match. Thank you!

[@g0od_0ne]

I just finished watching your old videos and let me tell you bro You look like a different man In a good way

[@PjotrII]

Thank you - your videos are interesting, you tell the information in a CLEAR pedagogical way, easy to understand still go into needed depth... very professional!

[@IsraelAndersonShow]

I think you're one of the best KZbinrs ever.

[@NonstickMilk]

Thank you for this information. I am designing a system that will not be permanent since I will be selling my home in about five years so I would like it to be portable. Thankfully I live in the desert where we get about 350 days of sunshine a year and it rarely dips below freezing. I will also be moving to another part of the desert when I retire in five years which is why I want to keep my system portable. Unfortunately, there are only a couple of solar contractors in the area who don't want to do anything other than their largest system at an ungodly price without taking into consideration what I am asking for. I understand that as contractors they are professionals and understand all the quirks that come with installing a system. But I live in a 1300 square foot home. I don't need the same system as those living in a 3200 square foot home. But the local contractors seem to offer a "one size fits all" package with a "take it or leave it" attitude.

[@DustDevilDan]

My Victron controller max input for my 24v system is 105v and 45 amps. My 4 panels are 37.5 v, 10 amps each so I could only connect two panels in series. I had plenty more room for more amps at 45amp max. So I connected two panels in series then another two panels in series for a total of four 250 watt panels. Then connected the two pairs together in parallel. That kept my voltage below 80v but brought the amps up from 10 to 20. It's working great running two freezers and a fridge in my shop.

[@neocrypto9368]

Will, long time subscriber and love your content! I just wanted to point out that with Delta Pro there are a couple potential issues running ~37 VOC panels in 4S or 4S3P. First, the MPPT in the DP is not all that tolerant above 150 VOC. It has a measure of OVP but somewhere between 150-160V (if you get a spike one cold clear morning, for example) the controller is apt to be damaged. Second, the MPPT tends to heat up and throttle somewhere north of 110 Vmp. Since running VOC close to the limit also means running >120Vmp (typically) there is a good chance 4S arrays are going to get throttled back to ~1200W or so during solar peak. In general, 3S2P of 300-400W panels in the low 40s for VOC tends to be fairly optimal for Delta Pro (as well as the Low PV input on the Delta Pro Ultra) in many climates. Other units (including the High PV input on the Delta Pro Ultra) may have better OVP and/or more headroom for VOC over the rated limit. DP and DPU are just what I am most familiar with and have a lot of experience testing.

[@LearnCreateLove]

Thanks Will for making this simple for the lay person.

[@johnwesterman]

Thanks for making it easy for us! One day soon I'll use all your support to build my own systems here.

[@Electronzap]

Good info. Power is probably one of the most confusing things for people newer to learning electrical concepts.

[@dekuramen3283]

I have two Delta Pro systems and interested in the Aptos panels. 400W with VoC at 37.18V is the sweet spot for sure. Thanks for discussing cold climate calculations as I live in BC, Canada. Do you know where could I find solar temperature information up here? 4 panels in series might be too much in -20C winters. Would it be viable to calculate the voltage drop in longer DC cable runs into the equation? Thanks Will, love the new content.

[@taylormkct]

Thanks so much, now I understand the set up, so I can confidently put my system up. Cheers Wil.

[@ddavis41]

For the EG4 reference, with the referred panels. The 6min 11max pertains to just one of the 2 mppts? So you would use 12 to 22 of the referred panels to run the EG4 correct? Thanks!

[@ddavis41]

Thanks for not replying to my question

[@ferguar4377]

Did you solve this question? I think your correct buy i had the same question

[@danielnicholls6868]

how about bifacials? they can put out a lot more in snowy areas do they bump up voltage?

[@kyleneedham6106]

Yes they should. But you would have to check the specifications on your panels. Not all are the same

[@PonoBill]

Thanks for the timely instruction. I'm building a tilting panel 2h X 12w on a 40 foot high volume container. I have a full pallet of Aptos 370W bifacial panels I bought at your suggestion (and with your affiliate link) ready to go. I plan to use two EG4 18K inverter and batteries so I can configure them as three-phase 208V to supply my shop. I hadn't considered temperature coefficient in my design and thought I had plenty of series voltage headroom with 12 panels per series string at a series voltage of 497V since the inverter handles 600V. I don't have a direct value for minimum temperature where I live but some research tells me it isn't less than 20F which is -6C. To be conservative I used -10C as an estimated value which yields 573V as a series Voc value for 12 panels. That's cutting it closer than I thought I was, but there's still room. Thanks again for the clarification and of course I'll buy the two 18K's and batteries with your affiliate link--it's the least I can do for your inspiration. I agree completely with your view on EVs. Not great looking cars and the Cybertruck is needlessly fugly, but it's relatively easy to power your own EV, so all the whining about how electricity is produces is just lame. I drive a model Y and consider it the best car I've ever owned. I raced cars for 30+ years and owned two Ferraris--I'm not comparing it to grocery-getters.

[@joeabad5908]

You are a good teacher.. I should know, though am an electrical engineer I am learning from you every time I watch your video. Thanks for the efforts.:

[@SuperSushidog]

I built a 48v system on my motorhome that has 8, 550w panels on the roof, wired in series which produces 400voc. My Sungold Power 5kw all-in-one's charge controller is rated at a max of 500v input, but its MPPT range only goes up to 450v, so this is the practical limit if I don't want it to truncate any power. However, in the real world, this horizontal mounted array typically produces between 265-375v. I had to wire them in series in a single string as the max amperage input of the controller is only 22a (though it has a 100a max output) and since the IMP of each panel is 13.45a, 2 strings in parallel would exceed the controller's 22a input current limit. I guess I could add one more panel to the string, but my 35ft coach's roof is completely covered now, reaching my physical limit before the electrical one. Though I do have a smaller 620w liftable array on the side of my MH to charge my smaller 12v 560ah battery.

[@bryanwi09]

Very helpful video. Thank you for explaining the calculations and the impact weather has on the solar output.

[@brushbum7508]

Thanks Will ! Have a great weekend. TAKE CARE..

[@Tanker_Wanker]

You break the info diwn so well for beginners. Thank you

[@pstoneking3418]

Very nice video. This could definitely prevent some damage to a beginners equipment.

[@sidperry7748]

Great teacher, love how he takes time and repeat to let our brains absorb

[@HartFarmsGenetics]

Thanks for all you do for the solar community

[@bradleybassett5900]

Good description, the only error I see is that you can use STC temp of 25°C instead of NOCT in your formula. As well PV modules rarely hit the voltage they're rated for unless your site is at higher altitude. I'll send my spreadsheet that I used for decades at work if I can figure how to.

[@Integritydefins]

Appreciate this video! Would love to see a solar install from start to finish. Installing everything right from the box step by step

[@diveswim]

This is great, there are way too many voltages to keep track of, this really help clarify

[@mondavou9408]

Perfect Timing! Thank you! This is exactly what I needed to understand the panel side of these systems.

[@Spaniard47]

it just so happens I bought ten of those exact Aptos 370W panels recently, and was curious about the real-world VOC data as it relates to ambient temps etc. Couldn't have timed the video better!

[@jurajveverka9011]

I am running EcoFlow Delta PRO with additional battery powered by three 510Wp (VoC = 45.85V, 14A) solar panels in series 24/7 for a year now. This system system powers core of my household (2x fridge with freezer, home office and computers, if excess power, than also washing machine and dryer or other appliances) and it works great and provides ~1MWh of electricity in a year.

[@funiroxic9977]

Bro, it took me years of saving up, but I finally got my own solar system of 200 W love to see how you change your systems up all the time

[@McTroyd]

A boat build channel I follow recently ran into that VOC limit of their controllers. They disconnected the battery bank from their charge controllers, leaving the panels connected, in full summer sun. Sparks and magic smoke emitted from a dozen or so blue Victron boxes. Fortunately the ending was a happy one, involving a GoFundMe-type thing, but I immediately thought of your channel when I learned of this. (They're bringing in pros to design the system, and make sure they've got appropriate fusing and disconnects.)

[@whattheschmidt]

Jesus...what a silly move lol. I installed my second array near dusk, being beyond extra safe because I didn't want to hurt any equipment. That's with Enphase micros too, very little risk at all with what I was doing.

[@McTroyd]

@@whattheschmidt To be fair, they're pretty clear about being DIY and not knowing everything about everything. Good people, just a bonehead move.

[@whattheschmidt]

@McTroyd oh, I'm sure they didn't mean to. It's just crazy no one thought about the power it was currently producing.

[@EsperanzaRMartnez]

I just purchased your book… it will be as a gift 🎁 I’m struggling with deciding what will be the best Solar panels and battery for my house… I just purchased a house in Arizona… I don’t trust the salesman 😢… please do a video off the for introduction to Solar it’s so much out there thank you 🙏

[@druggles1]

Thanks!

[@WillProwse]

Thank you!!

[@mattman6199]

Thanks that is the perfect example handling why and how to size.. and it helps you are using the exact equipment I am to use for your example… thanks

[@ericpeterson2936]

Bro. You are on fire with the EXACT necessary vids as of late. I already "knew" this info but the voltage was an assumption. The destructions of my Epever unit says 150v but nothing about "do not exceed!" Can I request some extra info? Language on fuses/breakers and WHERE to put them? In my original designs w 12v, I melted a fuse holder trying to run an A/C unit AND my overhead lights. Had I not been there, I would have burned down my shop as the draw was too much (hence my switch to 24v system now). I think fusing and circuit breaking is an overlooked safety device that if installed in the wrong spot can cause HUGE consequences. Thanks bud!

[@pandjnixon]

Hi Will, you've no doubt been asked this question before, but as I've tried to research it, I get a variety of different answers. - I have a 40amp Epever XTRA charge controller, to be used for a 24v system, that is designed for 1040 watts of PV input at 24v I will accomplish this using two off; 450 watt, 11 amp, 41.6volt panels wired in series, (string No.1 ) that I already own. However, I have four more identical panels, that I wish to add if possible, as series pairs, wired in parallel, as two more strings, for boosting the charge current x 3, in often cloudy weather. The question is; does the internal design of the charge controller, still regulate the output current to not exceed 40amps, into a half charged battery, irrespective of full sunshine hitting all 6 proposed panels, causing the voltage to remain high enough to push 100 plus amps into the battery if allowed to do so, from the additional panels, if the charge controller does not regulate above 40 amps output, whilst the (in this case), LiFePo4 battery is still charging ? So the question really is; does the charge controller, when its charging a half charged battery, in full sunshine, rely on the limited maximum current, of its prescribed 1040 watts of solar panels, so that in normal circumstances, it relies on the fact that the PV voltage will drop off sufficiently to thereby independently limit the charge controller's output, to a maximum of 40 amps ? Which therefore means its designed to only need to regulate the current once the battery reaches its nearly fully charged state ? Thanks for your thoughts on this.

[@johnhughes6847]

Hi Will, Great video as I needed some instruction on this. What about bifacial panels (Aptos 400W+) and on the 18Kpv not sure how things like nominal MPPT voltage plays into this (if at all). Thanks!

[@billsmith1647]

I would also like to understand how bifacial panel performance adds to cold temperature calculations affect panel count. For example; three strings of 530W bifacial with peak low temps reaching -25F several times during winter with rare dips to -30 and then some.... Rear snow reflection for 4 months etc.

[@chilimax21]

Thanks Will. Exactly the info i was looking for for my Ecoflow Delta Pro. Looking at you Aptos 400w panels!

[@clarencewiles963]

I still have your book Thumbs up 👍. But you could do a new book 📕 there are so many great new equipment.

[@jeffschroeder4805]

Solar in Minnesota is complicated by ridiculously low temperatures during the winter, effects from reflection off the snow and accumulation on the panels, as well as the significantly shortened days. The bi-facial panels you like might collect more energy reflected by the snow if mounted properly. I understand that solar installations were failing at first here because installers just used the standards from California where solar PV firstr became popular.

[@oscarb9139]

I am building an array(s) to feed an EG4 18k inverter. The string voltage is calculated to be fine with 13 panels, but the input amperage is half or less of the limit. Seems like there should be a way to maximize both. The Trina 245 watt panels produce 37.3 volts OC, and 8.47 Amps (short circuit) under standard conditions. The input limit is 31 amps on the mppt1 input. Seems like setting up 2 panels in the string with a parallel connected panel would get the amperage up closer to the limit. The plan is for (3) 13 panel strings feeding mppt 1, mppt2, and mppt3.

[@anonanonymous1988]

Hey Will, you should do a video on vertical mounted bifacial panels. According to what I've read, there's an output increase due to lower operating temperatures. This also reduces the horizontal footprint. You could have more panels in a smaller area (sq foot).

[@Onlyindianpj]

Finally a tutorial after so many months

[@teamfvbo9948]

This dude is the real deal.

[@waynejohn8]

Thanks. Your knowledge on this topic is phenominal! Much appreciated.

[@scientist434]

Thanks for this video, Really wish I had seen it 3 weeks ago before I bought all of my stuff. My system as I have it designed will have 102 Voc on a cold day in the winter and my Inverter can only handle 100 volts. Now I need to decided if I want to redesign my system or hope that I have 2 volts of voltage drop in my wiring.

[@amandaliberty08]

Will, you amaze me. Thank you for making that way less complicated than i was making it,

[@Jwall833]

Thanks for all your extensive knowledge and non biased reviews! Question: I have a solar panel that is too much voltage for my solar generator like a jackery or something, does it makes sense to use an mppt or pwm to make that useable power for the battery?

[@arte9855]

You explain this stuff in a way that i can comprehend it.😮 I'm starting to get the feel of this even if I have to watch it a couple times. Math isn't my strong suit 😂 I'm waiting for the light to come on and this stuff sinks in and makes sense.

[@lexxxus07]

Great video! Thanks for all the info! I am in a bad situation as I have limited space on the roof of the expedition vehicle, I can mount 3 large panels max and my AIO inverter accepts a range between 120v-500v in series.. Question is: is there a way to safely boost the voltage of the panels to reach around 200v for the string or, Alternatively install an a suitable mppt before the AIO system? Inputs would be highly appreciated!

[@dianaj3139]

This is a wonderful explanation for people like me! THANK YOU!!!

[@Just_An_Idea_For_Consideration]

SUGGESTION: Discuss when installing multiple but separate strings, orient all panels in one string as close together east and west, ie do not put in a single row east to west, so that as shadows hit the string, the strings that are not in the shadow area will have max production. versus if all panels are in a line the shadow will hit multiple strings at the same time, reducing production of all strings

[@jamesdean7756]

Huh

[@chrisk9351]

Thanks Will, videos are very informative. I am experimenting with the Oupes Mega 2 and a couple of extra batteries. It has the 150volt limit as well. I purchased 3 Talesun 400 watt Biracial panels with a VOC of 37.1, i wanted to ge 4 of them but that would put mw at 148.4 and I think that is to close to the limit. It gets cold for short periods in Arkansas so i guess sticking with 3 is the limit for now.

[@mrbigvanlife7130]

Another fantastic video Will, you’re a credit to the solar industry 🖖 👍

[@bubbaredneck75]

thank you for this.been trying to figure this out for acouple weeks now since i upgraded my system

[@timothyhoadley2432]

Will, you do a really great job working all the kinks out for us. Thank you! I do have a question though. Since the open voltage should only exist in an open circuit, could you use the rated voltage instead for the maximum voltage you wish to calculate? Again, thank you!

[@tonipanayotov8943]

Very clear explanation as always. But I would like to see systems with Enphase microinverters and Victron inverters on the channel. How to build a microgrid. I follow the channel with great interest. Thank you!

[@glyngibbs9489]

Thank you Will. Excellent work as usual. Can you do a vid on connecting panels directly to an ac appliance such as a water heat, so resistive load only please?

[@LADETROIT]

@WillProwse would laugh at my backyard ground system used to power my refrigerator and freezer. Here in Vegas. 10x 100 watt panels totaling five pair in parallel. Working fine for the past 3 years.

[@tinkering123]

Sounds like my Vegas backyard system. No way would Will pass me in his class room.

[@LADETROIT]

@@tinkering123 🤣

[@savagelexlex1296]

Well that video came in hot like a guardian angel, I just bought a property and the owner told me everything is setup so you can add more panel and more batteries to the current setup without any issue but I had no idea too many panels can fug up stuff, I didin't order them luckly and sometime it does get cold down to -35 -40 celcius. Thank you so much, probably saved some of my equipment because I have no idea what my solar controller can even do

[@chattphotos]

Every 3 years, it gets down to -12C/10F for a few days with the average temps being 25-33F I am probably limited to 8x 40V panels per series string, so it definitely is a balancing act to keep the inverter happy

[@jaytate491]

Wouldn't you be able to create "loss" by using a smaller gauge wire over a longer run and then go to 10 panels instead of 9 minimum? @9:05

[@johnhufnagel]

awesome video. looking forward to the parallel one. will you be doing one about dump load(s) in the future also?

[@emilecrotteau7312]

🇨🇦 THANK YOU,,THE ONLY THING I HAD NOT REALIZED WAS HOW MUCH THE POWER INCREASED WITH COLD WEATHER,,,AND THAT IS IMPORTANT UP HERE WE GET MINUS 40 C

[@mydogsbutler]

I'm in the process of designing my home solar system but I've heard conflicting information at times. For instance, while what you say about calculating max voltage of panels makes sense to me, I've also read elsewhere 20 to 30 percent above max mppt voltage is fine too. The argument given is the panels never reach their theoretical limit.

[@JanRademan]

My installer convinced me to go with 14 panels instead of the original quote of 12 panels due to shading concerns. My inverter lasted for only 12 months and packed up after the second winter. They reduced the connected panels to 11 when they replaced the inverter under warrantee (luckily). Based on these cold weather calculations, 13 panels would be redlining my inverter during the cold months. 12 would have worked, but I am sticking with the 11 active panels for now.

[@SkyCharter]

Excellent dude... I learned yet another solar particular today.

[@corsairusawc]

Hi, I love your videos! Why are my amps going up wired in series? Everyone says amps don't budge in series.

[@simonpaine2347]

Thanks again Will. Could you please explain how the twin inputs work on EG4 machines. When there are 4 inputs per MPPT i.e. 2 neg and 2 pos, how does that effect the calculations please? Does the inverter treat them as separate inputs, or are they simply combined? Thanks

[@SmoothLounge7]

So in winter disconnect two panels. In the summer reconnect them?