PV Basics: String Diode. What does it do, when to use?

[@Greenr0]

Great idea. Even if there is no shadow from the land, there could be clouds in the sky to shadow the panels. For safety and longevity, diode should be in all solar charging cables.

[@AlbertAmay-z6g]

Thanks for your video.its very useful

[@keithwingo514]

Roland, why don't we use diodes in other parts of the system design? For example, isolating all loads, so they can only ever pull from the battery bank.

[@RolandW_DIYEnergyandMore]

Diodes are valves which prevent backflow. Loads typically only cause flow in one way. You can use a diode for any application you find it useful, but you also need to understand that there is a voltage drop of around 0,5V over the diode. So it will cause power loss each time a diode is placed into a circuit.

[@netrocker9990]

Clean the panels🙄

[@AlbertAmay-z6g]

Sir is it also applicable to series connection and how does it connect.also in positive side only

[@RolandW_DIYEnergyandMore]

Hi, if you only have one single serial string of panels connected to one charge control input, then you do not need a blocking/string diode. The Charge controller will prevent backflow into the panels. String diodes are only there to prevent one set of panel push back power into another set, when they are connected in parallel.

[@romans4471]

Hello Roland, First of all I must say I really admire Your knowledge on one hand but also Your knowledge sharing efforts in Your videos. Thank You very much for this. In relation to thi video topic, I'm just wondering why do we use DC cables of a 4-6mm2 gauge to connect the PV equipment, but then - in the middle of this connection - we can install such a diode with its very thin connectors? What's Your opinion on this? Is it safe ? Normally I would say we need to keep the rule of at least 1mm2 gauge for each 10A of the current.... PS. I would appreciate if You could use a mic that would be closer to You so the videos do not contain so many background noises which obviously makes is harder to listen and understand ;-)

[@RolandW_DIYEnergyandMore]

When we choose wire gauge, it is all about savely transporting energy over a distance while not losing more then a certain percentage of that power. Special components which need to be included in circuits, are only required to perform as they are rated. Let's say a switch must be able to carry 20A, a breaker as well as specified, etc. In the case of our diode, it is the same. It must only hold up until the rated current. The internal wiring will be OK because the wire length is very short. Surely such components are acting as obstacles inside of the circuit, and they will as well be the breaking point before anything will ever happen with your wiring. I know the sound on older videos isn't best as at that time i didn't have a mic yet. I hope it is better on newer videos. Thanks for watching!

[@romans4471]

Thank You. BTW. Do You use a standard rectifier diode or a special type diode called Schottky diode? The second one should give you a lower voltage drop in the forward direction - so the lower warming up.... But as it is only 0,5V vs 0,2V so I'm not sure if it is worth of trying.... A specially that in my installation I have the string voltage at the level of 450V what implies of using diodes dedicated for such a voltage range and this causes a problem because I was not able to find out the diode of the cylinder shape as all of them are produced with this TO-220-2 package (dedicated for electronic plates ) which makes it hard to install within the solar energy equipment.... :-(

[@RolandW_DIYEnergyandMore]

@@romans4471 those MC4 diodes are a finished product. I don't know what is built in inside. Probably a Schottky. I think I also have some Schottky Diodes laying around somewhere if I need to replace a burned-out Diode. Just always try to use a Diode with a very high current rating, like 30A or so...

[@adamelkoumy5141]

Thanks for the great video. Please keep giving us more

[@RolandW_DIYEnergyandMore]

Thanks Tommy, if there is any topic you would like to know more about, please let me know.

[@maheshindrasingha5923]

Sir.. I have 60W 2 panels (voc-22v, vmp 17.2v) and 195w one panel (voc-45v vmp-36.6) .. Can I use 60w panels series and parallel with 190w panel for 24v system ? *with inline 10A blocking diode

[@RolandW_DIYEnergyandMore]

hi. yes. you can use that combination

[@maheshindrasingha5923]

@@RolandW_DIYEnergyandMore Thank you ❤️🌟

[@Steveuploads]

I can imagine calling a guy in would probably result in him replacing the panel. How does a faulty diode manifest itself as a problem ?

[@RolandW_DIYEnergyandMore]

Those 3 panels in line with the diode did not produce current because the circuit is disrupted. In my case with 5 parallel strings, I have lost 20% output on the whole system. That's why it is very important to at least write down monthly generation in a excel table to compare to the same period of years before. Only this historical data was telling me something is not correct...

[@zarbonida]

You can also check wires from the panels with an ampmeter clamp to see how many amps are flowing

[@Xoda_]

Do I need fuses or blocking diodes? I got 6x 100W solar panels, planning a 2 in series and 3 in parallel. What is the difference? Thanks.

[@RolandW_DIYEnergyandMore]

Fuses protect against over-current due to shorts, blocking diodes prevent against current back-flow. You should always use a fuse. Blocking diodes only if you have a shading issue or the individual parallel strings are facing different directions.

[@Xoda_]

@@RolandW_DIYEnergyandMore My concern with using a 10A inline fuse is that my series strings of 2x 100W have only about 5A Imp. So at 2s3p if one panel's series faults, will the 10A from the other two series strings be enough to pop the fuse of the panels series with fault? 10A at Imp, it can be lower than that most of the time. Thank you for taking the time, truly appreciated.

[@RolandW_DIYEnergyandMore]

@@Xoda_ Hi. It is correct that it will be very unlikely that a 10A fuse will ever pop. your strings will hardly see 4A going over them. I would use a 6-7A fuse in your case.

[@Xoda_]

@@RolandW_DIYEnergyandMore Do you have a specific model of the MC4 inline fuse holder you would recommend or store that has them? I'm really struggling to find a definite answer about which holder is of good quality and which ones aren't. I guess I'll need to find a source for these 6-7A fuses. Again, Thank you for taking the time. Much obliged.

[@RolandW_DIYEnergyandMore]

@@Xoda_ This would be an example for a 6A solar fuse: www.aliexpress.com/item/4000885582182.html?spm=a2g0o.productlist.main.55.42aa16acwhbitJ&algo_pvid=aa3ff11c-5698-4925-8838-694c1d4828ba&algo_exp_id=aa3ff11c-5698-4925-8838-694c1d4828ba-27&pdp_npi=3%40dis%21THB%2124.19%2124.19%21%21%21%21%21%40211bd93f16809050988321690d0778%2110000010316976805%21sea%21TH%21185638773&curPageLogUid=rKJgxhd5Z4ve This the standard fuse holder (its Din rail, no MC4 inline): www.aliexpress.com/item/4000845692965.html?spm=a2g0o.detail.0.0.4f6e4152tsoyty&gps-id=pcDetailBottomMoreThisSeller&scm=1007.13339.291025.0&scm_id=1007.13339.291025.0&scm-url=1007.13339.291025.0&pvid=62d6f161-ac91-4ed6-907b-3c3fdd807a03&_t=gps-id:pcDetailBottomMoreThisSeller,scm-url:1007.13339.291025.0,pvid:62d6f161-ac91-4ed6-907b-3c3fdd807a03,tpp_buckets:668%232846%238116%232002&pdp_npi=3%40dis%21THB%2124.19%2124.19%21%21%21%21%21%402101c5ac16809052490287528ec7e1%2112000026743480327%21rec%21TH%21185638773 You should get something like this on every mayor online store

[@offgridmangogrower]

Enjoyed your instructional video The in-line looks easier and faster to install….I noticed a huge battery bank loss recently during a moon lite night…and suspected back feeds thru the solar chargers(maybe the internal diodes are compromised or have worn out in 10-15 yrs of usage. I hit the breakers in the evening and measured the voltages in the mourning and bingo.

[@RolandW_DIYEnergyandMore]

Yes, usually charge controllers should prevent backflow during the nighttime. String diodes are definitely a second line of defense.

[@stevelamperta865]

solar panels come with diodes already on the back ! These diodes are for the very thing you just explained . Why would you add yet another diode inline of the solar panel ? It wont do anything .

[@RolandW_DIYEnergyandMore]

Bypass Diodes are used in parallel with either a single or a number of photovoltaic solar cells to prevent the current(s) flowing from good, well-exposed to sunlight solar cells overheating and burning out weaker or partially shaded solar cells by providing a current path around the bad cell. Blocking (String) diodes are used differently than bypass diodes. Bypass diodes in solar panels are connected in “parallel” with a photovoltaic cell or panel to shunt the current around it, whereas blocking diodes (or string diodes) are connected in “series” with the PV panels to prevent current flowing back into them. Blocking diodes are therefore different than bypass diodes although in most cases the diode is physically the same, but they are installed differently and serve a different purpose.... as said, blocking or string diodes are only needed in a constellation of multiple parallel strings on one charge controller. If there is backflow into one string due to individual shadowing from trees, chimneys, poles, etc. that power would not go to your charge controller, instead it would be burned off at the shadowed string and you lose overall output power.

[@zarbonida]

How far from the panels is it possible to install an mc4 blocking diode? If hot temperatures outside are damaging your diodes (every two years), is it possible to install them inside your house (with cooler air temperature)?

[@RolandW_DIYEnergyandMore]

Theoretically it wouldn't matter where you are putting it, but in systems with parallel strings, you are typically combining the outputs of those strings somewhere outside at the mounts in a combiner box. So the diode will be before the combiner box. You would have to install that one indoors then as well. The diode only costs a few dollars. Much cheaper then pulling more cables as home-runs...

[@bengrobben2582]

hi, where did you buy the blocking diode? i can only find them on ebay and amazon. buts i dont trust how good these are. thanks

[@RolandW_DIYEnergyandMore]

Hi, i probably bought them on AliEx. Will be same as Ebay and Amazon

[@budmartin3344]

Great video. What is the spec of the diode, and part number? Thanks.

[@RolandW_DIYEnergyandMore]

Those diodes come with current ratings from 10 to 30 Amps in 5A steps. You can get them at you favorite online store.

[@farmerbloggers9026]

4 panel of 100w with parallel what size of blocking diode

[@RolandW_DIYEnergyandMore]

do you have a shading issue? 4x 100w panels are a fairly small array. aren't those panels next to each other and going into shadow at same time? otherwise the smallest diode like a 10A will do it...

[@farmerbloggers9026]

@@RolandW_DIYEnergyandMore yes ser same wattage of 100watts but,the other one it defferent of ,imp,voc,isc

[@RolandW_DIYEnergyandMore]

@@farmerbloggers9026 if you put panels in parallel, then at least the Voc of all panels should be about similar. Slight differences are no problem. But if those 4 panels are just mounted right next to each other and facing the same direction, then you might save the blocking diode as all panels will be illuminated the same way at same time anyways. Blocking diodes make sense when parallel panels look different directions or do expear different shadowing situations over long time.

[@farmerbloggers9026]

how many blocking diode can use of 4 solar panel in parallel

[@RolandW_DIYEnergyandMore]

@@farmerbloggers9026 you will need 4 diodes. one for each panel in parallel

[@zarbonida]

How many voltages are you loosing with blocking diodes? What was the Voc and Vmp voltages per string before and after?

[@RolandW_DIYEnergyandMore]

Schottky diodes typically have a 0.3-0.4V drop over them. My Voc on that system is around 135V and V during normal operation around 100V

[@zarbonida]

@@RolandW_DIYEnergyandMore thanks Roland. I am subscribe your channel. Now i am going to work (it's morning in Italy) but i am very happy to find you. Very good contents! I will see all your videos next days. Bye, see you

[@beppe8585]

Hi, Thanks for the video. I wanted to ask you a question, maybe you could help me. I have two strings of solar panels in parallel, each strings with two 250W 36Voc panels in series, around 60v 8A each string maximum. I have two options, install a Schottky diode 10A 50V (10SQ050) or a 30A 1000V rectifier diode (30A10 MIC). Which one would you recommend? Thanks for your amazing videos.

[@RolandW_DIYEnergyandMore]

hi. schottky diodes usually have lower forwardvoltage drops then rectifier diodes so you would lose less power with them. the 10A is a bit close to the limit tho. but still, you could go for it...

[@beppe8585]

@@RolandW_DIYEnergyandMore Thanks for the super-quick reply!

[@beppe8585]

@@RolandW_DIYEnergyandMore Last question. Would be a 15A 45V Schottky diode be ok for those strings? I wouldn/t want to blow them up, since the voltage going through would be around 60Volts....I believe the 45 V in the Schottky diode refers to its maximum voltage, but online there isn't much information....

[@RolandW_DIYEnergyandMore]

@@beppe8585 i don't think that the voltage rating is much of a concern in this case as there will not be a lot of reversed voltage in a PV string. The diode is only used as a directional valve. Once the sun isn't shining anymore voltage in the array will drop and maximum reverse voltage will be the battery voltage.

[@zynskavzynskav4465]

Do you install bypass diode?

[@RolandW_DIYEnergyandMore]

Bypass diodes are installed inside the junction box of the solar panel by the panel manufacturer. Without them a panel would block current flow in case of partial shadowing.

[@zynskavzynskav4465]

@@RolandW_DIYEnergyandMore so is this enough or do I need external bypass diode when connecting 2 solar panel in series?

[@zynskavzynskav4465]

@@RolandW_DIYEnergyandMore ok, so, blocking diodes still needed right? For parallel solar panel

[@RolandW_DIYEnergyandMore]

@@zynskavzynskav4465 yes, you still need blocking diode when you have parallel strings. And No, you don't need any extra bypass diodes. That is taken care of by the panel manufacturer. Cheers!

[@zynskavzynskav4465]

@@RolandW_DIYEnergyandMore Thanks 🌅

[@kendalsari]

thanks for the video 👍

[@RolandW_DIYEnergyandMore]

Thanks for watching!

[@athulaj9319]

What is this country

[@RolandW_DIYEnergyandMore]

Thailand

[@athulaj9319]

@@RolandW_DIYEnergyandMore looks like sri lanka.thats why asked!