Before you keep commenting, that panels have diodes included in the connection box. Yes, they have but they are bypass diodes, *not blocking diodes*. This is a total different purpose.

@willtaylor8904

3 жыл бұрын

Can you explain the difference?

@offgridwanabe

3 жыл бұрын

@@willtaylor8904 Here is what google says Blocking 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 are connected in “series” with the PV panels to prevent current flowing back into them.

@neliosamch3195

3 жыл бұрын

High quality monocristaline panels don't need blocking diodes to prevent batteries from discharging. But bypass diodes are included on all newest panels to prevent over heating and fires.

@OffGridGarageAustralia

3 жыл бұрын

@Phil Ware There is a big difference between these two.

@Sylvan_dB

3 жыл бұрын

@@neliosamch3195 The "prevent batteries from discharging" function is provided by the charge controller.

To put this difference in diodes in perspective... the 'bypass' diodes built into the solar panel are arranged in the 'blocking' direction, but they bypass the cells in the panel meaning that they do not prevent the reverse voltage from being applied across the cells. This is why these bypass diodes are not blocking diodes. They don't block anything... they are designed to allow current to bypass a shaded cell. The solar panel cells are natural diodes on their own, but they will not have the high reverse breakdown voltage spec needed to prevent current flow in the reverse direction through the panel. Even worse, if the reverse voltage hits that breakdown threshold, the panels can basically become a dead short with all the energy being dissipated by the cells. This is why fuses or blocking diodes are recommended. Blocking diodes are usually Schottky power diodes (0.4V forward voltage drop). The wattage of the blocking diodes you get must be in excess of the 0.4V x MAX-AMPS going through a single string, and the reverse breakdown voltage of the diode must be well in excess of the worst-case (highest) open-circuit voltage for a string. Now the question as to whether you need blocking diodes or not: Generally speaking, if you are paralleling single panels and then putting the parallel group into series (i.e. one actual string), it isn't a big deal and of course a lot of energy can be lost forcing a 0.4V drop across each element of a series configuration. But if you are trying to parallel whole strings (where each string contains several panels in series), THEN you want a blocking diode coming off of each string. One blocking diode for each string. Two strings, two blocking diodes. Schottky power diodes (0.4V drop instead of 0.7V drop). You will lose some of your solar energy, but not much. For example, if the working voltage of the string is 80V, the 0.4V drop means you lose only 0.5% of your solar energy. I will add here, that it is the delta reverse voltage that matters. If one string is partially shaded then it will still develop some voltage across the panels so the reverse voltage will be decreased. If one string is fully shaded then a higher reverse voltage will exist across the shaded string. MORE IMPORTANTLY, if the charge controller is charging the battery, it will DRAW DOWN the voltage on the sunny string so, again, the reverse voltage across the shaded string will be lower. YOU NEED TO DEAL WITH THE WORST CASE SITUATION. The worst case situation is when your batteries are full, the charge controller is not drawing any current, and the sunny string is developing its full open-circuit voltage while the shaded string is fully shaded. The reverse voltage will be at a maximal value under these conditions and potentially be too high for the shaded panels to be able to handle. As a secondary note, the breakdown voltage might break-down the natural diodes in the silicon in the reverse direction with very little current, allowing the open circuit voltage to remain high until such a point when all the diodes in the panels on the shaded string are in the reverse-voltage break-down state. At that point the entire shaded string can potentially become a dead short. This will finally draw the voltage from the sunny panel down from its open-circuit value to a lower value, which may or may not take the reverse breakdown out of the dead-short. Either way, it can cause serious problems for the shaded panels. -Matt

If you need a diode, you would need it for both strings (in the vertical leg above each string, not just the horizontal leg between the two strings).

What a whirlwind of emotion. You did a test on something I didn’t know I needed to worry about, made me worry, and then said everything was okay.

Another video from Off-Grid Garage. It makes me happy.

@OffGridGarageAustralia

3 жыл бұрын

Thank you.

The bypass diode on the rear of the panel is to keep the electrons flowing through the solar strings when the controller is switched of. It also allows a positive charge to keep adding to the flow. You do not need a blocking diode it is not necessary as you just proved. If you are concerned about the milliamps that your losing you have a problem not the cuircut. Well done Andy keep up the great work.

Helo from Canary islands-Spain. The reverse current problem occurs when we have more than two series since the current can be high and exceed the maximum allowed by the panels (Modules Series Fuse).

Great test and video, I was just thinking about this very topic if you can back feed a solar panel, Thank You so much for sharing your solar journey. I learn more from your solar videos in real time, rather than just an abstract tutorial. You have such an enjoyable, inquisitive presence and you articulate so well the subjects you discuss.

@OffGridGarageAustralia

3 жыл бұрын

Thank you so much, Jim. Much appreciated!

Wow, what an amazing video! I think you already learned about the bypass diode, however, I think also that at 3:05 your MPPT is looking for the correct voltage without system damage which is what shows your temporary loss in wattage. Also I think the MPPT/inverter does prevent the "Christmas tree" effect in addition to, obviously, the bypass diode. What a great video, I couldn't find anything else like this, thank you.

Ohhh - He learned the "Kirchhoffs law" today. WOW ;)

I think what you mean about those diodes is that they are installed to prevent short circuit in one string to affect the other. Think like 2 bateries, if one shorts the other will feed current to it.

@OffGridGarageAustralia

3 жыл бұрын

They can prevent a short if you have one faulty panel in one string. That's why it is important to check regularly on your system to see if there is an issue with the solar production.

I think modern panels have the diodes built into that connection box on the back. So "there in there".

@junkerzn7312

3 жыл бұрын

No, those are bypass diodes. They are going in the blocking direction, but the bypass diodes do NOT prevent current from back-flowing through the cells on the solar panel itself. -Matt

Note that if the charge controller is drawing current from the 'sunny' panel string, then that string will not be at its open-circuit voltage and the reverse voltage on the shaded string will be lower... possibly even low enough to not even be a reverse voltage any more. Test the worst-case situation, which is: (1) Batteries are full and the charge controller is not pulling any current from the panels (2) One string is in full sun (3) Shaded string is fully shaded That's about the worst-case situation. If you only have two strings and only a few panels in series on each string, you might not have a problem. But if you ever expand the array beyond that, things get dangerous without blocking diodes. For example, if you have three strings, the current from two of them can gang-up on the shaded string. If you have long series strings, the high open-circuit voltage can cause very large reverse voltages on the shaded string and if that ever goes into cascade failure your roof could end up on fire (though, at least, if you have fuses, blown fuses would be the more likely result). Either way though it isn't good. But still, I would recommend putting in two blocking diodes (one for each string) if you want to tie the strings together. Or use two separate MPPTs. -Matt

There's one way to solve your shading problem - A chainsaw! 🤣

@richardsirois6975

3 жыл бұрын

An electric one, powered by the battery!

Good shade ing test. Never seen a test like this before. Brilliant KZreadr Andy. Keep up the good work. 👏🏾🙏🏾🇬🇧🇯🇲👊🏾

Like your videos so much, decided to start from the beginning and binge watch your videos. Not much of a battery guy but do like these Panel tests. Thank you!!

Thanks a bunch! This is exactly what I was looking for.

Always enjoy your video 😀

Ian H Tried this experiment a few years ago. Two used (~8 year old) 100w panels connected in parallel, one face up in sunlight one face down so totally dark. Put a digital ammeter between the positives of the two panels (panel nearest to charger was face up - as in your diagram). I read 7mA back feeding into the dark panel at around 19v. Panels in use were 4x9 configuration of monocrystaline cells rated 23V @ 6.5A. Box on rear of each panel had two diodes, both bypass for each 2x9 section of the panel. Not sure if more modern panels act differently now, but I guess the laws of physics have not changed that much? As for blocking diodes, I wonder what their reverse leakage is, probably a bit less than 7mA, but I’m personally not going to lose any sleep over such minimal losses. If people are that worried about this the solution is simple, multiple MPPT controllers (Victron allow this), one per string. Combine the outputs as you plan to do via breakers, problem solved!

@zarbonida

3 жыл бұрын

Thanks for sharing your experiment. Good to know. I was asking to Andy if it possible to repeat this experiment (single pv shaded) but with the battery full (so solar charger doesn't accept any current from the pv panels). I don't have any answer. I am only curious to know what ampmetric clamp says about the current flows in the pv wires in this scenario (battery full, no loads, single string shaded)

diodes are very important! that is why they are mounted directly into each solar panel at the connection level. that way shading affect only panel in one given series. good show!

Thanks for the information 👍

Good test.

The main issue with parallel panel/strings with partial shading is it screws up the controllers MPPT point finding which causes unshaded panels to also produce less output. Best solution (besides eliminating partial shading situation), although more costly, is one series string per MPPT controller, same as for groups of panels facing in different directions.

@OffGridGarageAustralia

3 жыл бұрын

I agree, I made a video about this a while back and asked the same question: How many MPPTs would I need? kzread.info/dash/bejne/qqKo2tyync3SqLA.html

Thanks, you saved me $25!

Super Test, schön bewiesen .... 10/10 Mythbuster Points👍

Andy, in your test the battery wasn't full and solar charger was producing energy. But, what will happens if the battery is full? Where current will flow? In to the shade panels that has less voltage? Can you do a test with full battery and an amperometric clamp in the pv wires?

@OffGridGarageAustralia

3 жыл бұрын

As the battery fills up the controller reduces the power coming from the solar panels by moving the them out of the maximum power point, so driving them less in a less efficient are of the curve so to speak. As I said in the video, I don't think you can have such a big difference in shading from one string to another on the same roof. And if so, it maybe worth installing a separate charge controller for that scenario.

@zarbonida

3 жыл бұрын

@@OffGridGarageAustralia that's true. It is only to see what will happens in this scenario: you are not at home, the battery is full, no load in the inverter and a bird shit shades a pv string. What will happens? Nothing or something in the pv strings? i am afraid for the Voc full shine string that will be a little bit higher than Voc pv shaded. (Solar charger is in standby cause the battery is full). So what will happen to the current of the pv string in full sunshine? Will it flow a little bit to pv string shaded? Or nothing? So, please. For the love of the science, Can you repeat your pv single string shaded test with full battery and no load in to the inverter? (Using amperometric clamp in the pv wires)

Solar Panels are more like *Current* *Sources* , so when connected in parallel, the Amps ADD together as they find a common voltage ...

Hi Andy, I think the blocking diode is a relict of the ancient time of solar power...I had a 12 v panel with 50 Watts...years ago ..connected direct to the battery of my camper...then you could loose some energy over night when you forgot to disconnect ...the blocking diode was the solution that time.....

Hey thanks man... Have a nice Christmas.. Peace Rolf

Hi Andy. I think you have diodes in the cable box on each panel. Than you for great videos.

Thanks .. learnt a good lesson 👍

(Sorry for my english) Andy you did a very good test. The reason why the current doesn't go to the shade pv panels is because bypass diodes help themeself to stay at high voltage (around 100V). So the current will flow to battery (48V)

@OffGridGarageAustralia

3 жыл бұрын

That's actually not true. There are bypass diodes in every panel but you would have only one blocking diode per string.

I read somewhere that reverse current is only a problem if one string is completely dark, which would never happen in real life, so those few mA that might flow between strings would not justify blocking diodes in my opinion. The only bad thing that happens with shading in parallel strings, is the different mpp's of each string, but that is a different story. Great video.

Yes Test 👍 ⚡ 🔌 💡

Nice vid.maybe the effect is higher when a diode of the panel itself is broken.? Just an idea.if all is ok,you showed it well

If u wanna use diodes , or Replace Bypass diodes in panels (black box on the panel backside) Look into SM74611 It's a replacement for a normal diode but has almost no loss.... regards Joe

@jonathanalcocer3872

3 жыл бұрын

Too low reverse voltage, those only can take 30v reverse so it would not protect in the situation of power flowing from one string to the other Edit: while loaded his string seems to output about 70v, 3 diodes in series, one in each panel, should be able to stand that but when the load is low or there's no load the open circuit voltage might be high enough to blow those diodes

@MrSummitville

3 жыл бұрын

@@jonathanalcocer3872 I think, your analysis is 180° backwards. It is the voltage across the "string of cells" being bypassed inside of the panel, that is not allowed to generate more than 28 Volts. 40 cells per string (max) = 28 Volts / 0.7 volts-per-cell. Actually, that is a very high number of cells to protect in one "string of cells". When the sun is SHINING - then the device has a REVERSE Voltage applied. When the "string of cells" is SHADED - then there is only a small 0.4 volt FORWARD voltage drop across the internal body diode ...

@jonathanalcocer3872

3 жыл бұрын

@@MrSummitville What I was talking about is the maximum reverse voltage those diodes he referred to can block the open circuit voltage of those panels is 40v I think and the diode with that reference number can only take 30v in reverse.

@MrSummitville

3 жыл бұрын

@@jonathanalcocer3872 Again, there is NO Reverse Voltage on this DEVICE when the Solar Panel is SHADED - it is a *Forward* Voltage! The Reverse Voltage occurs when the sun is shining and the "string of cells" INSIDE that panel are actively producing volts & amps. This device can withstand 28 Reverse Volts from the "string of cells" located inside that panel = 40 Cells max protected. You are very confused, as to when there is a Forward Voltage vs a Reverse Voltage across this device and where those voltages come from ...

Gut 👍😊

So from this we see that the diodes in the panels work. A string is still part of the circuit as they usually share a ground, so the whole panel can be bypassed. What you may notice is a few lost volts (about 0.6 per panel/diode).

Could you explain the difference between blocking and bypass diodes? Thanks.

@OffGridGarageAustralia

3 жыл бұрын

Yes, it seems I will make a quick follow up video tonight. I thought this is all common knowledge but so many people get this wrong...

power will flow towards the controller as the potential is lowest there. A diode can't hurt, although you have the small loss in forward voltage, but I don't know if it is vital.

@OffGridGarageAustralia

3 жыл бұрын

You will lose around 0.3V over a diode. Multiply this by the current of 8A in my case and you will lose 2.4W. However, the lower voltage will also start you charging later and end it earlier. Not sure how much energy you will sacrifice there over time.

the bypass diodes are already installed in the panels junction box (when the panels are not cheap).. the utility is to « bypass » the current flow when a panel have a shadow in a serial configuration (as 3 battery in series, the max current is drived by the weakest battery).. so under shadow, those diodes skip the panel and it’s better than to lose all the series (if panels voltage = or > than the battery voltage, in your case with 2 panels on 3 availables).. a solar cell is already a diode (a panel is a lot of diodes/cells in series) and i don’t know why a serial diode could be necessary in parallel configuration..

Most of the panels nowadays have these bypass diodes built in. Plus solar radiation density in W/m(squared) doesnt affect the putput voltage of the panels! It only affects the output current! The open circuit voltage of the panels stays pretty much the same, unless the solar radiation intensity that hits them is exptemely low, or you load the circuit and pull the voltage down.

@OffGridGarageAustralia

3 жыл бұрын

Yeah, they all have bypass diodes but not blocking diodes. different things...

I always thought it was voltage that mattered in this scenario and that it will take the path of lease resistance

@OffGridGarageAustralia

3 жыл бұрын

Voltage does matter. Current always flows to the lowest point of voltage which is the charge controller.

@ahmadplastiq2067

3 жыл бұрын

@@OffGridGarageAustralia really...lowest voltage..erm..how come?

@TheGalifrey

3 жыл бұрын

@@ahmadplastiq2067 ohms law in the same way a battery will charge when the voltage input exceeds the voltage of the battery. The amperage then depends on the voltage level above that battery. (watts = volts x amps)

Wow that's super interesting! No loss whatsoever. I wonder if the theory of having 3 panels in a series is a bad idea. Some say no way don't do it. But I think it's worth a test possibly. 🤔 Cheers Andy ⛅🌞

@OffGridGarageAustralia

3 жыл бұрын

With a 48V battery, your panel voltage needs to be far over that voltage or your could not charge. If it's only for a 12V system, you can parallel all panels and don't need to worry about shading or diodes. But you have much more cabling effort.

@DavidLouthan

3 жыл бұрын

@@OffGridGarageAustralia yes outstanding for my 12v system that is what I'd try it on . Eventually it will be upgraded to a 24v (cells are on the way, maybe here in 2 months lol) but that's more project for next year. Got my first testing of the system today with running all the pond equipment and it passed with flying colors! I was Bing watching your build and victron videos all day. Gotta learn the best settings for the lifepo4 from your testing and study 📖. Thanks man, cheers 🌞

I always thought the diode was already in the panel junction box but it may depend on the make of the panel.

@OffGridGarageAustralia

3 жыл бұрын

There are always bypass diodes i the box behind the solar panels, not blocking diodes.

I measured back current on my parallel panels sets caused it's lower output voltage than higher voltage sets in parallel. My panel sets point SE or SW so output varies. I use one schottkey at the end of each set. You must measure to know!

@MrSummitville

3 жыл бұрын

Note: His panels are side-by-side, they not pointed in two vastly different directions SE vs SW ) like yours are...

There should be diodes already built into your panels anyhow. But you can blow them out if you have more current going back to them than what your max fuse rating is for your panels

@OffGridGarageAustralia

3 жыл бұрын

Nope, that is not correct. They are bypass diodes, not blocking diodes.

the black box on the back of panel already has the diode in it. it also prevents reverse current.

@OffGridGarageAustralia

3 жыл бұрын

No, that is wrong. These are bypass diodes in the connection box, not blocking diodes. Bypass diodes are not for blocking reverse current!

@MrSummitville

3 жыл бұрын

@Phil Ware More likely, he will have only Bypass diodes ...

“Let’s do the test.” = Why I watch. This is actually a very complex question to answer theoretically. Depends on many things. I believe (haven’t done the test) that parallel strings of different nominal voltages (number of cells) can backfeed many amps when unloaded and in full sun. Conversely, modern half cell panels and shingled panels are arranged as multiple smaller panels connected in parallel without blocking diodes and this helps with shading. Another thing to ponder is that a shaded panel cools down which increases its open circuit voltage. Shaded does not mean complete darkness.

@OffGridGarageAustralia

3 жыл бұрын

You should not parallel strings with different voltages ever! That could cause a fire unless you have installed such blocking diodes. There are bypass diodes and blocking diodes for solar panels but they are different things.

I think your charge controller will have the blocking diode to prevent current being drawn from your battery to the solar panel. Otherwise at night there would be a drain on your battery because of the voltage difference. However your panels will have the bypass diode to prevent current going to the shaded panels.

@OffGridGarageAustralia

3 жыл бұрын

The controller does not know how many strings I have connected in parallel. This would not be working to have this installed in the controller.

I have a set of very old panels (HF 45 watt) without bypass and blocking diodes. I have a newer set of 100 watt panels that have the bypass diodes. Fyi.

@OffGridGarageAustralia

3 жыл бұрын

Thanks Peter.

Your Video looks much clearer on my Laptop than other Videos . May i ask for information on your cam gear ?

@OffGridGarageAustralia

7 ай бұрын

I'm using a GoPro Hero 8 Black for 99% of my recordings.

I thought the blocking Diodes were to prevent battery discharge at night ( with dumb charge controllers) but new charge controllers have diodes built in to them to prevent this. I have not seen a need for diodes in the systems these days. But I only know from my experience with a "small" 2kw system.

@habana7638

3 жыл бұрын

All 60-cell solar panels consists of three strings, and therefore has three diodes in it, for partial shade..

Please try out a scenario when the battery is full and current has no where to go but to the shaded panel. Iam sure you will get different results

@OffGridGarageAustralia

Жыл бұрын

Nope, it's not a different outcome. Once the battery is full, the SCC will drive the panels away from the maximum power point to make them 'inefficient'. Because all solar strings are in parallel, they have the same voltage. Same voltage does not trigger any current. Even if the shade is changing due to wind and moving branches from the trees, the voltage across all strings is always the same. In such a scenario, one string could have a slightly higher voltage for a moment and may be able to see a very small current from one string to another but we're talking about less than 10mA for a brief moment.

The unloaded cell voltage is much higher than cells at max PPT, so it makes sense that you need impossibly extreme shading to bring a string's output low enough to become a problem under normal circumstances. It is more of a "best practice" thing in case a panel shorts out than an absolute necessity.

@OffGridGarageAustralia

3 жыл бұрын

That would be a different scenario, yes. I have seen pictures of that but never heard or read about it actually happend to someone.

Diodes are useful between series panels but that test would require lots of rewiring. If you had diodes wired in parallel between the series panels you would get more than 30 watts from the shaded string.

Hi Andy! Wery interesting video. Iv been serching for this informaition for a long time. I aprishiate You for your grate experiments and alot of job for making this videos! I have an idea -so we can connect 2 or 3 strings in parallel and orient them to West, South and East and get power all the day? For example main string 1500Wt PV array to the South and additional array arond 1000Wt to South East to get additional power in the start of the day, and additional PV 1000Wt to the South West for additional energy in the end of the day?

So what about explaining bypass diodes? I would have thought too you should get a bit more with some panels shaded if the bypass diodes are working. Is the voltage going below the minimum voltage for the regulator? It is good to see no need for blocking diode. I understood that blocking diodes are only for night losses. Charge controllers generally have that built in now.

@OffGridGarageAustralia

3 жыл бұрын

The bypass diodes are only effective if you have a shadow on one panel of a string. Otherwise the panels in sunlight would push their current through this shaded panel and could heat it up. These bypass diodes are installed in ever panel already (see all the comments here). A blocking diode has a different task though and prevents one string feeding another string. The bypass diodes would not help in this case.

@jasondevine6014

3 жыл бұрын

@@OffGridGarageAustralia yes, but you only got 19w off the other panel, in theory if the mppt has enough voltage on rest of panels in string you should get the power from the unshaded panel in that string. You are correct but if you have time a video would help some I think it seems many don't understand the bypass diodes proper function especially if you have say 150v string voltage.

Dont the panels have increased resistance when shaded?

You would need TWO diodes, one per string btw. I am no expert, but as you found ,you really do not need them because the voltage output is high enough. it's the current that mostly goes up with intensity of sun rays. It's a quantum thing, and maybe there is a youtube video out there explaining this?

Diodes prevent backflow. No one will argue against that. But is it necessary? But without diode, if one of the string is shorted, it too will short the other strings and possibly permanently damaging them or worse cause fire. If there were diodes, it will block the short.

You should have measured the open circuit voltage of the shaded panels. If that is higher than the MPPT voltage of the un-shaded panels, you are golden.

@OffGridGarageAustralia

3 жыл бұрын

It must be. Otherwise there would be no current flowing from the shaded string to the other one. Voc is always higher than Vmp.

@kevinmills5293

3 жыл бұрын

@@OffGridGarageAustralia but the shaded VOC may not be. Clearly it must have been in this case but did you actually measure it to see what it was?

@OffGridGarageAustralia

3 жыл бұрын

Yes, it was visible when I connected the shaded string to the charge controller. At the beginning there is no current flowing until the SCC picks it up.

Diod overload, me my diods!

in that fuse boxes you close and open . what fuse do u use ? ? you explained it in another episode but cant remember in where in the PILE of episodes !!! ..

This video is old news now that you have your new installation… however - it would have been more illustrative if you had actually placed a blocking diode in the circuit and not relied on supposition to arrive at your conclusion. Theory is nice, to a point.

Question: besides a small voltage drop, is there any other disadvantages to including a blocking diode with each string?

@OffGridGarageAustralia

2 жыл бұрын

No, no disadvantage at all.

My panels all have reverse-blocking diodes in them already Andy, I think it's fairly standard. Maybe look in the junction box on the back of the panel?

@OffGridGarageAustralia

3 жыл бұрын

They have bypass diodes, not blocking diodes. Don't mix this up 😉

@maleiot_83

3 жыл бұрын

@Phil Ware a normal diode has + and - connections..you also have a blocking direction and a forward direction (means conductive).... the bypass mode is the "forward direction"....the diode is connected between + and - from each panel.......in normal conditions (when u have sun) the blocking direction voltage is approximately the open circuit voltage of your panel --> panel works....but if the shading occurs, the voltage of your panel drop...then the forward dircetions comes to work...so bypass....or bridged....

@maleiot_83

3 жыл бұрын

@Phil Ware If you know how a diode works, then you have the answer of your question...a diode can bypass or block...in bypass mode is a short circuit between + and - ..so the current can run the way through the diode and not trough the panel...

@maleiot_83

3 жыл бұрын

@Phil Ware no problem...i wanted to explain the diode in blocking direction...in a solar panel the diode is normally connect in blocking direction...electricity flows through the panel...in bypass mode the electricity flows through the diode and not trough the panel...so the panel is bridged...that is what i want to say... :-)

@davebodger2

3 жыл бұрын

@@OffGridGarageAustralia Fair do's

The wealth of information I have learned from you is great. so much. but can someone tell me If there is a charger that I can connect to an MPPT charge controller, so I can take advantage of all the adjustable parameters . Sorry if I asked this before, I forget. But it is bugging me and I have yet to get a reason why I can't do this, but lots of "NO's"........

@OffGridGarageAustralia

2 жыл бұрын

Thank you. You want to connect a power supply to a solar charge controller? I don't think that's a good idea as the MPPT would try to find the best power point of the power supply. It's not designed for that. You usually use a power supply with a fixed voltage and limited current to charge the battery accordingly as per its specs.

@immrnoidall

2 жыл бұрын

@@OffGridGarageAustralia If you got an extra one lying around, try it. People like me would definitely tune in to like it. Just think. If you found a combo that worked, you'd be a hero. All those parameters. Just think of the possibilities for the common folks. LOL Or let out the magic smoke. Either way clicks ahoy. In the name of science.

@OffGridGarageAustralia

2 жыл бұрын

@@immrnoidall What would be the benefit of doing this though. The power supply needs to have a current limiter anyway otherwise the MPPT will short it as it tries to pull as many amps as it can. But if the power supply has a current limiter, we can can use it directly to charge the battery. Constant Current, right? So, I'm not sure why you need the MPPT then? OK, the parameters you can set... but that's it?

Hi Andy. I always thought that modern solar panels had diodes built into them.

@BenCos2018

3 жыл бұрын

they do

@OffGridGarageAustralia

3 жыл бұрын

They have bypass diodes, not blocking diodes.

@BenCos2018

3 жыл бұрын

@@OffGridGarageAustralia ah Thanks for the info

@maleiot_83

3 жыл бұрын

@@BenCos2018 cause the diodes are wired in blocking direction.....:-) take a look in the junction box and u will see...

@BenCos2018

3 жыл бұрын

@@maleiot_83 yep Reliased my mistake after I commented lol

Nice experiment, but what happens when you disconnect the MPPT, e.g. for maintenance purposes, and one string is shaded and the other is not? Can the current flow from the unshaded string to the shaded one damage the panels?

If you actually need to add a diode, you would have to add 2. 1 in each string. But most panels already have a schottky diode built into the output junction box on the back of the panel. One place you would need to ensure there is a diode is if you have a panel directly connected to a battery, but who does that. There should be a charge controller in the circuit.

@MrSummitville

3 жыл бұрын

These panels do not Blocking Diodes ...

I think I may have a situation where you need a blocking diode. I have 2 solar panels on my 4wd one on the bonnet and one on the rear window. The rear window is on an 80degree angle to the sky and the bonnet is on a 20 degree angle to the sky. Therefore in the morning the sun will hit my rear windscreen deed on but the cab of the car will shade my bonnet. At midday my bonnet will get direct sunlight and my rear panel a little bit of sun but in the afternoon my bonnet will get sun but boot panel will be completely shaded. Do I need blocking diodes for this situation and if I don’t install them can I hurt my shaded panel. I have 1 110w panel and 1 160w panel. Both at 21v

Well... usually if you have multiple strings you get a charge controller that has separate input terminals (and a separate MPPT) for each string. You can also just get a second charge controller and connect the battery side in parallel with the first, each charge controller handling one string. In the latter, the settings on the two charge controllers must be precisely the same and a non-zero absorption time should be set (at least to some low value, at a minimum), to give both charge controllers a good chance of staying synchronize with each other if there is no smart communication between them. If there is smart communication between them, then you don't have to be as careful. Generally speaking you do not want to tie the strings together, but it depends on the configuration. If you only have a few panels and the voltage isn't too high, then it will probably work. It just won't be optimal if one string is shaded and the other is not. At higher open-circuit voltages, though, the reverse voltage on the shaded string can be substantial and it's a really bad idea to tie the strings together. At least, I wouldn't do that. My recommendation is that you purchase a second Victron SmartSolar charge controller. I'm not entirely sure if the one you have (the MPPT 150/35) can synchronize multiple units or whether you need something like the SmartSolar MPPT 150/100 - Tr VE.Can. You can, in fact, use a second MPPT 150/35 and just keep them dumb and unaware of each other... it won't be perfect, but it will work fairly well. In terms of using power Diodes, if you tie the strings together using diodes you need one diode on each string (two diodes total), and the diodes have to be able to dissipate the maximum per-string current across the (typically 0.4V or 0.7V depending) voltage drop and have a reverse-breakdown voltarge well in excess of the open-circuit voltage of the strings. You lose some of the solar power when you diode strings together that way due to the voltage drop across the diode. It's usually better to have multiple MPPT charge controllers or one charge controller with multiple independent MPPT string inputs. -Matt

@zarbonida

3 жыл бұрын

With lithium battery, you don't need to synchronize the charge controller (as in Pb battery). It's better to have different voltage set-up beetween several solar chargers to reduce flow current at high state of charge

@junkerzn7312

3 жыл бұрын

@@zarbonida That kinda makes some sense except the worst case current is still going to be with both charge controllers in bulk with a low battery. I don't think any massaging of settings avoids that case. But in terms of Float and Absorption settings, I do see wiggle room. -Matt

@zarbonida

3 жыл бұрын

@@junkerzn7312 i am not sure understand you. Why do you want avoiding bulk phase in two or several solar charger with a low battery?

@junkerzn7312

3 жыл бұрын

@@zarbonida The maximum current the two MPPT charge controllers can ever deliver to the battery will occur during the first half of the bulk phase with the battery at a low state of charge. The charge controller will be in Constant Current mode (that is, whichever cap comes first... current or voltage, is what the charge controllers will deliver, and in this situation it will hit the current cap first). In this first part of the bulk phase the battery is in a low or medium state of charge, not a high state of charge. Multiple charge controllers WILL gang-up on the current so this is the state that you have to be careful about, to ensure that the combined current does not exceed 0.5C. By the time you get to a high state of charge, the charge controllers will have already gone into Constant-Voltage mode. When the charger controllers are in Constant-Voltage mode, it does NOT matter how many charge controllers you are running in parallel. They will all output the same fixed voltage and the current will be limited by what the battery accepts. This is what 'Constant Voltage' mode means. The battery is governing the current acceptance at this point, not the charge controllers. Since the current is limited to what the battery accepts, the current (which will be well under 0.5C at this point) will not add up with multiple charge controllers. The multiple charge controllers will simply take a share of that acceptance current. -Matt

@junkerzn7312

3 жыл бұрын

@@zarbonida I think something is getting lost in translation here. I never said anything about avoiding the bulk phase. I simply stated that when one has multiple charge controllers connected to the same battery, the maximum current going into the battery will be during the first part of the bulk phase. And I explained why. -Matt

I have 540W×10 same as two parallel, currently one string one panel damaged. Can I keep 9&10 parallel.

Two strings of panels require two MPP controllers to optimize the power. You may be lucky and the panels match some times, but to ensure maximum power, each string needs it's own MPP.

@MrSummitville

3 жыл бұрын

Is the extra cost worth a few extra percentage in watts = pennies ?

Hi Andy, Correct me if I am wrong - but if you shaded only two of three panels in your 660watt string you should have close to 220watts from the remaining panel via two in series bypass diodes reach the inverter? To get only 32watts as you did from the remaining unshaded panel in your string test indicates most solar power generated is being lost as heat! Either via faulty "bypass diodes" or via the shaded panels themselves? Normally forward biased power diodes drop about 1volt which means each diode will need to be rated at minimum 10watts to prevent overheating and failure. Personally I suspect the bypass diodes don't actually work in your system - leaving you with the resistance of multiple solar cells or failed high resistance bypass diodes getting very hot in your recycled and shaded panels. It needs checking or you could have an unexpected fire! Naturally this reasoning is utterly dependant on the readings you get from your Monitoring software utility being accurate when you shade your panels? If the readings are not accurate as you drop the string voltage to 1/3rd normal the whole test is meaningless anyway LOL :) By the way as a final friendly comment - if you want to protect your strings from back feeding you need two blocking diodes one on each string, not just one on one string. Cheers :)

In your diagram, the two panel strings combine to feed the controller on a common circuit, but your installation has the two strings on separate circuits; that is why you do not measure a need for the blocking diode - that functionality is handled in the Victron box ;) [edited because I kant spel]

@OffGridGarageAustralia

3 жыл бұрын

That's not the case, both solar strings are connected in parallel to the same SCC.

@ZookeeperJohnG

3 жыл бұрын

@@OffGridGarageAustralia Ahh, two parallel strings and circuit protections, but electrically bonded @ the SCC which are not then isolated inputs. :D

it's in the pv panel box ! Probably one blocking diode & one bypass diode per panel .

@zarbonida

3 жыл бұрын

there are only 3 bypass diodes in the pv box. No one blocking diode

@gd2329j

3 жыл бұрын

@@zarbonida Depends on the panel !

@zarbonida

3 жыл бұрын

@@gd2329j can you tell me a pv panel with a blocking diode?

@gd2329j

3 жыл бұрын

@@zarbonidaSunpower used them .

@MrSummitville

3 жыл бұрын

@@gd2329j Blocking Diodes were used when the Solar Panels were specifically designed to be directly attached to a battery bank, without a charge controller, that is very rare now. The following SUNPOWER Solar Panels do *NOT* have any Blocking Diode ... SPR-E-Flex-50 watt SPR-E-Flex-100 watt SPR-E-Flex-110 watt SPR-E-Flex-170 watt So, which model of Sunpower solar panel did?

So what is the Voltage of the panel string that is shaded?

@OffGridGarageAustralia

3 жыл бұрын

You can see the numbers in the mobile app

How about an MPPT controller for each string?

@OffGridGarageAustralia

3 жыл бұрын

Yep! kzread.info/dash/bejne/qqKo2tyync3SqLA.html

Nice video, displacing those old recurring foibles. Accepted knowledge is always based in old technology, and thence out of date.

@OffGridGarageAustralia

3 жыл бұрын

Well said!

What happen if disconnect mppt and repeat this between strings just

@OffGridGarageAustralia

2 жыл бұрын

That's a different issue. We may see some current from one string to another. But, at what stage would that happen in real world. The SCC is always connected.

@factoryautomation2385

2 жыл бұрын

@@OffGridGarageAustralia what is scc

having different strings might actually decrease the overall efficiency if they have different lighting because the MTTP will optimize on the two strings not knowing about then. As far as I understand it, if two strings have significantly different lighting, using separated MTTP might improve the efficiency. (These are only assumptions, I am not knowledgeable enough about these systems)

@OffGridGarageAustralia

3 жыл бұрын

Yeah, I discussed this in a previous video a while back (kzread.info/dash/bejne/qqKo2tyync3SqLA.html). Then you spent all the money on more charge controllers, cabling and accessories to squeeze out a bit more power or have them in parallel with less effort and run them in a bit less efficient way. It's a difficult decision, right? And how do you test this? Would need term a long term setup to compare both situations over time.

I have connected solar panels in parallel, on one string, can I connect one more powerful solar panel on the same string in series?

@OffGridGarageAustralia

Жыл бұрын

I would not recommend that. Very hard to get the exact matched solar panels which could make this work.

We have to remember that every cell in the solar panel is a diode. How many cells in a solar panel? Plenty of them that it produces bigger voltage and current than a single diode. Current always go to the least resistance, that is the charge controller then the battery so I will not worry much of anything that goes back as there is almost nothing that goes back. When one does not even use a charge controller and connect the battery directly to the solar panel, it also works well and no one is talking about diodes. Again, a solar panel is already a bunch of diodes in series and all glass packed diodes when exposed to light will produce voltage and current will start to flow to the least resistance path when there is one.

@absolute___zero

13 күн бұрын

yeah, but because every cell is so tiny its reverse breakdown voltage is low (not the same as breakdown voltage of schottky diode which is 1000 volts) so if you over-serie-over-parallel your setup you can break the diodes of the solar panel and it will become as conducting as a copper wire, so all the power you are collecting from the sun will be burnt on the shorted panel. Or worse than that, you can break only part of the panel, and this one part will be short circuiting the whole array of your parallel-serie configuration, the ugliness is that you aren't going to know it unless you do very scrupulous testing

Are your two strings connected in different charge controllers? Or they are first connected in parallel and then connected into a controller

So, if you can "backfeed" the panels with voltage and current, will they then produce sunlight? ;)

@OffGridGarageAustralia

3 жыл бұрын

That is a very good question! 🌞

@Gnagnie

3 жыл бұрын

No Dave, they produce heat (thats one way to get your panels free of ice and snow)

@davecrook9313

3 жыл бұрын

I suppose that if you feed in enough power they will produce light, when they catch fire. don't try this at home people.

@andrewsweet43

3 жыл бұрын

actually solar panels can kinda work in reverse and produce infrared light like leds. The thing is that they are TERRIBLE at doing it...! Most of the power will be converted into heat and probbably damage the cells.

@MrSummitville

3 жыл бұрын

@@andrewsweet43 Heating the panels with reverse current was actually an idea tried by Midnite Solar !

The solar panels already have diodes in the little black box on the back of the panel

@MrSummitville

3 жыл бұрын

Usually only Bypass diodes, not a Blocking Diode ...

Why do you need a breaker for both the positive and negative. Don't you only need one breaker to the positive??

This would/could also prove you can have different strings with different sized panels ... i.e. one has three 100W and the other has two 100 watts? right?

for the last 20 years a diode has been fitted to every panel made . it is fitted in by the wires coming out of the panel.

@OffGridGarageAustralia

3 жыл бұрын

Read the pinned comment at the top.

Hi Andy, you can't listen to all people's recommendations. That diode is stupid, of course, but you've already found out. Every good (standard) panel has such a small black box from which the wires come out. This box contains, among other things, rectifier diodes. So you don't need another diode. But as you found the disadvantage of strings in series is that when only one panel is shaded, the performance of the whole string drops to almost zero. Therefore, it is not very involved in connecting many panels in series.

@MrSummitville

3 жыл бұрын

But those are not Blocking Diodes, they are Bypass Diodes ...

Most manufacturers place diode‘s in the solar panels because of that possibility happening of power back feeding.

@zarbonida

3 жыл бұрын

False

@corybodiker6243

3 жыл бұрын

Every panel I have ever bought has the exact set of three diode‘s in it any panel that does not have them it’s probably of the worst quality. You get what you pay for.

@zarbonida

3 жыл бұрын

@@corybodiker6243 they are bypass diodes! Not blocking diodes

@OffGridGarageAustralia

3 жыл бұрын

That's exactly right @zarbonida. So many people get this wrong and I thought it's common knowledge hence I didn't mentioned it in the video.

i thought all relative current panels have diodes build in .

@OffGridGarageAustralia

3 жыл бұрын

they are bypass diodes though.

@houseofancients

3 жыл бұрын

never knew that.. thanks andy !

Hi. Can I use our video for Turkish dubbing? Turkish. For Turkish people to understand

Most good panels have diodes bilt into the little box on the back of the panel

@MrSummitville

3 жыл бұрын

Usually only Bypass diodes, not a Blocking Diode ...

People that think this don't understand electricity. Even a shaded panel produces a voltage to high to allow current to flow in from a lower voltage source. Every panel today comes with a diode installed. It's there to simply keep the battery from back feeding at night. Sure, it helps with mismatched panels too.

@MrSummitville

3 жыл бұрын

Usually only Bypass Diodes, not a Blocking Diode ...

Doesn’t each panel already have blocking diodes.

@OffGridGarageAustralia

3 жыл бұрын

No, they have bypass diodes only.

@MrSummitville

3 жыл бұрын

@Phil Ware What is the mfr & model # of the Solar Panel that you have that contains a Blocking Diode? And what YEAR did you purchase it ?

@MrSummitville

3 жыл бұрын

@Phil Ware He talking about *EVERY* Solar Panel that is designed to be connected to a Charge Controller or an Inverter. Which is 99.999% of the Solar Panels that are made in the entire world. So, what kind of "word game" are you trying to play?

@MrSummitville

3 жыл бұрын

@Phil Ware He talking about *EVERY* Solar Panel that is designed to be connected to a Charge Controller or an Inverter.

I don't understand why diodes are in solar panel systems to begin with, because solar cells are light receiving diodes. Basically the opposite of an Led.

@longwhitecloud

3 жыл бұрын

That is correct, the only problem is that the reverse breakdown voltage of the intrinsic diode-junction in the solar cell itself is that it breaks down at anywhere between 15 and 60 volts. Most panels are strung with much higher voltage so the intrinsic diode-junction in the cell is not sufficient. BTW as a LED, if you feed back into a solar cell, it will emit infra-red light - not very efficient at that though ;-)

Most panels already have diodes, some have multiple diodes, preventing the backfeeding within the panel,