Biggest Solar Panels...

[noelex 77]

There are some advantages to the larger 2x 100/50 controllers. As Jedi points out, if one controller fails the output of both panels could be connected to the remaining controller with little loss of output. This can also be done with the 100/30, but there would be more loss in solar production. The larger controller will run cooler (Victron controllers only have passive cooling and can get quite warm). This would probably help reliability. Finally, if the panels are upgraded for a larger model the controller will still have enough capacity.

While the above benefits are real, I don’t think the extra cost of 2x 100/50 over 2x 100/30 controllers justifies these benefits, especially as there would be no practical gain in normal output.

Originally Posted by CaptainRivet

If there are serious cost constrains and we are talking about FLA battery bank then you are right, get 2x30/100...if you have lithium or plan to upgrade to it get the 2× 50/100.

Why does the battery type make a difference? If anything, the slightly higher and stable voltage of lithium under load means the battery voltage is less likely to dip below the 12.2v point where, if the solar panel was delivering its full 365w, the solar controller would be reaching its limit.

[CaptainRivet]

Originally Posted by noelex 77

There are some advantages to the larger 2x 100/50 controllers. As Jedi points out, if one controller fails the output of both panels could be connected to the remaining controller with little loss of output. This can also be done with the 100/30, but there would be more loss in solar production. The larger controller will run cooler (Victron controllers only have passive cooling and can get quite warm). This would probably help reliability. Finally, if the panels are upgraded for a larger model the controller will still have enough capacity.

While the above benefits are real, I don’t think the extra cost of 2x 100/50 over 2x 100/30 controllers justifies these benefits, especially as there would be no practical gain in normal output.




Why does the battery type make a difference? If anything, the slightly higher and stable voltage of lithium under load means the battery voltage is less likely to dip below the 12.2v point where, if the solar panel was delivering its full 365w, the solar controller would be reaching its limit.

If he gets bifacials half cut cells in 365W he will reach the limit of 30/100 quite often if the battery bank allows that charge...as said i see daily 440W from that panel during noon times. My buddy boat installing them had the same issue and replaced the 30/100 with 50/100 when he got the longli bifacials.


Your kidding Battery type matters a lot, solar smashes in full output till LFP bank is at 98% (depending on your absorbtion settings in your MPPT or BMS if LFP) means solar runs on max it can deliver till bank is full, no limitations.
Depending on size if FLA bank it might not even cannot take the full 60A+ out of the solar or you cook them and if you can only delivers full power solar if below 12.2V, from 80 to 100 it takes ages with FLA.

Sorry we are talking about 100 per MPPT more, if you are that broke consider selling the boot, thats peanuts in boat money. You already regretting now to have too small MPPTs as you need new ones, getting 30/100 you will regret with next repaneling.

[rslifkin]

I agree that the 100/30s should be adequate. I have a pair of them with a 410w panel connected to each (not bifacial). I've seen slightly more than rated output from each of them at times, but I've never hit the 30 amp output limit on the controllers. The closest I've ever seen it get was 29.6 amps.

Theoretically the controllers are limiting in my setup, but in practice, by the time you're far enough into the day for full output from the panels to be possible, the voltage has come up enough that you won't achieve 30 amps even with 400+ watts going through each controller. In reality, I rarely see more than 300 - 350 watts out of each panel unless I'm running a heavy load at the right time of day, as a combination of imperfect weather and the charging cycle of the batteries means that I'm in absorption and the amps are tapering off (AGM batteries) by late morning before the sun is high enough to make full output possible.

Given a big enough battery bank (and drawn down far enough) relative to the size of the solar install, the controller limiting output situation would be more likely to occur, as you'd be charging at full output later into the day.

[CaptainRivet]

Originally Posted by rslifkin

I agree that the 100/30s should be adequate. I have a pair of them with a 410w panel connected to each (not bifacial). I've seen slightly more than rated output from each of them at times, but I've never hit the 30 amp output limit on the controllers. The closest I've ever seen it get was 29.6 amps.

Theoretically the controllers are limiting in my setup, but in practice, by the time you're far enough into the day for full output from the panels to be possible, the voltage has come up enough that you won't achieve 30 amps even with 400+ watts going through each controller. In reality, I rarely see more than 300 - 350 watts out of each panel unless I'm running a heavy load at the right time of day, as a combination of imperfect weather and the charging cycle of the batteries means that I'm in absorption and the amps are tapering off (AGM batteries) by late morning before the sun is high enough to make full output possible.

Given a big enough battery bank (and drawn down far enough) relative to the size of the solar install, the controller limiting output situation would be more likely to occur, as you'd be charging at full output later into the day.

How do you know that your 30/100 didn't reduced the charge, it does that automatically when you are close to the limit and you don't get any error like overload...if you hit rating on a 410W panel it already did. Maybe it didn't because this 50 W too much gets wasted by voltage drop on your installation, easly happen on a 10m run one way...

And then you sit the day arround with fully charged battery and waste the energy solar could deliver the rest of the day??? Right its AGM it needs to be fully charged....

If my LFP bank gets near SoC 80 the water heater kicks in, after that i run watermaker and or washingmaschine,the dishwasher, the breadmaker, the icemaker, give the freezer an extra cold boost or cook a roast in the inverter oven. All the time solar contributes full power what the panels and MPPT can deliver, rest comes from bank. I always find something to burn the energy solar delivers if the bank is nearly full.
Soon a 24V aircon for owner cabin will definitly eat all i can give to it.

[noelex 77]

Originally Posted by CaptainRivet

Your kidding Battery type matters a lot, solar smashes in full output till LFP bank is at 98% (depending on your absorbtion settings in your MPPT or BMS if LFP) means solar runs on max it can deliver till bank is full, no limitations.

It is a good point about bifacial panels, the output from the rear of the panel needs to be considered when sizing the solar controller, but SailingHarry is not looking at bifacial panels.

In terms of lithium batteries, I still don’t see how this requires a larger solar controller in this case. Solar controllers are not like alternators. They can deliver their full rated output all day long without any issues.

The only concern with the 100/30 is if the 30A output is enough for a 365w panel. Here the battery voltage is important. If the battery voltage is very low and the panels are delivering a very high output, the required output current may conceivably briefly rise above 30A. The battery voltage has to be below 12.2v (if we assume a 365w input) for this to happen.

This could occur if a high load was placed on the battery, such as the inverter running a high draw appliance at the same time as the solar panels were delivering their full 365w or higher output. If this happens it will not damage the controller, but a small amount of energy could be lost, although this will never be more than a tiny amount for a short time.

If a high load is placed on the batteries the voltage drop will be higher on lead acid batteries than lithium batteries. You are more likely to see a low battery voltage, such as below 12.2v, with a lead acid bank than a lithium bank. So in this case I think changing to lithium would help rather than hurt the 100/30 controller work well with the system, although this controller would be fine for both battery types.

[CaptainRivet]

Originally Posted by noelex 77

It is a good point about bifacial panels, the output from the rear of the panel needs to be considered when sizing the solar controller, but SailingHarry is not looking at bifacial panels.

In terms of lithium batteries, I still don’t see how this requires a larger solar controller in this case. Solar controllers are not like alternators. They can deliver their full rated output all day long without any issues.

The only concern with the 100/30 is if the 30A output is enough for a 365w panel. Here the battery voltage is important. If the battery voltage is very low and the panels are delivering a very high output, the required output current may conceivably briefly rise above 30A. The battery voltage has to be below 12.2v (if we assume a 365w input) for this to happen.

This could occur if a high load was placed on the battery, such as the inverter running a high draw appliance at the same time as the solar panels were delivering their full 365w or higher output. If this happens it will not damage the controller, but a small amount of energy could be lost, although this will never be more than a tiny amount for a short time.

If a high load is placed on the batteries the voltage drop will be higher on lead acid batteries than lithium batteries. You are more likely to see a low battery voltage, such as below 12.2v, with a lead acid bank than a lithium bank. So in this case I think changing to lithium would help rather than hurt the 100/30 controller work well with the system, although this controller would be fine for both battery types.

Well sailinghary should look for half cut cell bifacials, i explained why, helps to solve or reduce a lot of his shading and performance problems.

Read my poat above again and carefully, then you know why it matters. Even your bank won't accept full output of MPPT you just add a load like watermaker and MPPT raises to max MPPT/Solar can give you.
Well WH per day per MPPTs raised a lot since i have LFP ( same 3x50/100 MPPT) can easily see at on the stats of the victron...thats real life not theory. Charge efficeny is already much higher on LFP.

Well throwing up to 4,9kw inverter at 12V at lead bank would end in a Desaster....you simply can do much more with LFP then with a lead bank and burn more energy.

[rslifkin]

Originally Posted by CaptainRivet

How do you know that your 30/100 didn't reduced the charge, it does that automatically when you are close to the limit and you don't get any error like overload...if you hit rating on a 410W panel it already did. Maybe it didn't because this 50 W too much gets wasted by voltage drop on your installation, easly happen on a 10m run one way...

And then you sit the day arround with fully charged battery and waste the energy solar could deliver the rest of the day??? Right its AGM it needs to be fully charged....

If my LFP bank gets near SoC 80 the water heater kicks in, after that i run watermaker and or washingmaschine,the dishwasher, the breadmaker, the icemaker, give the freezer an extra cold boost or cook a roast in the inverter oven. All the time solar contributes full power what the panels and MPPT can deliver, rest comes from bank. I always find something to burn the energy solar delivers if the bank is nearly full.
Soon a 24V aircon for owner cabin will definitly eat all i can give to it.

I do end up wasting power, as the solar is enough to get the batteries topped off on any decent day, meaning we're not getting the most out of the solar. So we try to do higher power stuff in it afternoon so it uses that surplus.

As far as limiting or not, I've watched the output current. It's never quite hit 30 amps, even while showing that I'm at or just above the panel rating. Panels any bigger than mine or a big battery bank that might be at lower voltage when you get to the peak power time in the day would lead to hitting that 30A limit.

[sailingharry]

So, some random responses to a lot of posts. It's long, apologies.



First, a really interesting tidbit on the size of the MPPT. Victron has a calculator. You put in all kinds of information about your panels, series/parallel, all the tech specs. It suggests a MPPT controller. I even picked the largest panel in the line that I was looking at, 380W. Two in P, and ran it as two in S. Victron recommends the 100/50. If you then go into the details, it specifically states that the solar array is 10% oversized for the recommended MPPT. So they are comfortable recommending a MPPT that will see throttling. The issue, I think, is that they recognize that a 10% loss for the small period of time that it occurs does not justify the next size up. Now, they didn't consider recommending splitting into two panels with two MPPTs. The next step up from the 100/50 ($300) is the 150/60 ($539). And there is a lot of discussion on the Victron forum of arrays that are sized for winter (low output) but 2-3 times the controller ability in the summer, with no issues.


There has been a lot of discussion on my budget. I never made it above middle management in my career, but am quite comfortable financially and have a comfortable retirement. I did this by ALWAYS considering financial implications. I can and do spend money. But I have never bought into the "this is one place you shouldn't skimp" (which is recommended in almost any conversation....LOL).


Rivet suggested I should oversize because I'm already regretting my choice of to buy the two 75/15, and reuse the existing 10A Genasun on my installation a mere 18 months ago. I'm not regretting! If I hadn't slid my boat into a concrete wall in 6 knots of current, requiring me to completely replace my arch and everything on it, I'd be happily using what I installed for a decade to come. But since I'm getting a new arch built, I have a lot of choices. And one of them is to make changes. But if I simply upgrade the one small panel (limited by something that is changing), and upgrade its controller accordingly, I'll have 600W in three fully independent systems, for a mere $300 out of pocket. Or I can, as I'm considering, push it to 730W (a whole 130W of power!) for a bit more. I still don't really know if 3 independent panels will avoid the backstay better (and provide more power) than two larger panels. I think the odds are high that one of 3 will always work -- and also high that certain sun angles will mostly kill two larger panels from backstay shading (but that may be an unusual event). With two panels, I can go a single 100/50, for $100 more I can go 2 100/30, and for another $200 more (a total of $300 more than a single 100/50 that is a 95% solution) I can go with two 100/50's. If I go from 3 panels to 2, the choice is a single 100/50 or two 100/30s -- two 100/50's don't meet the value threshold.



I currently have AGM. As pointed out by some, this will suck down almost anything my solar array can provide. I can routinely put over 50A (or 650W) into my AGM up to a bit over 90% SOC. Since I rarely get over 90% SOC, an LFPL won't take any more power than an AGM. However, I'm also intending to build an LFP bank this winter. As Noelex has pointed out, LFP will virtually eliminate the issue with the MPPT capacity. At 3.2V/cell (sort of a low-but-not-out value), an LFP will sit at 12.8V. At 50A output, a 100/50 can support 640W before it even begins to throttle. Although with my 740Ah AGM bank and modest loads, I rarely see a battery voltage below about 12.2 (I rarely hit my 3KW inverter with more than a toaster, and my windlass at 1kW or so only hits it for minutes at a time). And as Noelex points out, these momentary drops in voltage truly won't hurt the MPPTs. So in the morning, before voltage starts to come up, a 50A controller can support 610W.



Rivet keeps harping on half-cut bifacials. I'm intrigued. I'm having two issues -- cost (they seem about double single monofacial) and size -- I'm trying to maximize my capacity within my area. Solar vendors do a really good job of obscuring size -- they love to give lots of other specs, but size requires opening the listing, finding the size, realize they don't fit, lather-rinse-repeat. GRRR. I really want to keep my panels under 70" long and 41" wide.


Rivet has also commented that at peak sun, when the batteries are starting to reach full, he has lots of high power uses to put the energy to. We don't have as much flexibility. Our water maker (in 4 years of ownership and 8000 miles of cruising, I tested it and re-pickled it) is a low power 12V unit that doesn't draw much. Since we tend to move daily, our hot water is almost always hot from the engine. We cook on propane (and when we use our electric coffee pot and toaster, we don't have surplus sun!). So excess solar, which happens VERY rarely, is just...excess.

[GreenWave]

So I have been told that the amp value in an MPPT spec is the max that it can pass to the batteries. A 100/30 cannot pass more than 30 amps. If more than 30 comes into it the MPPT will cut it off. The voltage value (100] is the max that can come into the MPPT. This should not be exceeded

Have I been misinformed? If more than 30 amps comes in then you aren’t doing anything bad you are just losing some power.

[s/v Jedi]

Originally Posted by GreenWave

So I have been told that the amp value in an MPPT spec is the max that it can pass to the batteries. A 100/30 cannot pass more than 30 amps. If more than 30 comes into it the MPPT will cut it off. The voltage value (100] is the max that can come into the MPPT. This should not be exceeded

Have I been misinformed? If more than 30 amps comes in then you aren’t doing anything bad you are just losing some power.

You have misinterpreted it. MPPT does not pass amps at all, nor does it pass voltage. You must look at it as passing energy.

If you have a panel that outputs 375W and your batteries absorption voltage is 14.4V then the amps going out is 375 / 14.4 = 26A. A 100/30 MPPT can -output- a maximum of 30A so it’s good.

The number for voltage is the Voc of the panels. If putting panels in series this comes into play. Also, the panels themselves have a maximum “system” voltage which is about wiring- and construction insulation rating and diode ratings.

The Victron regulators automatically limit and de-rate themselves so you can use controllers that are too small to pass available array power… you simply let some power go to waste. Shameful but technically allowed

My recommendation for the larger controller is for a list of reasons including easier future upgrades, possibly bifacial panels (up to 30% extra output) and reserve capacity in case another controller fails.

[fxykty]

Originally Posted by GreenWave

So I have been told that the amp value in an MPPT spec is the max that it can pass to the batteries. A 100/30 cannot pass more than 30 amps. If more than 30 comes into it the MPPT will cut it off. The voltage value (100] is the max that can come into the MPPT. This should not be exceeded

Have I been misinformed? If more than 30 amps comes in then you aren’t doing anything bad you are just losing some power.

You’re correct, the MPPT controller will cut off any excess current at its maximum. Note that is output current, not input. Nothing bad will happen; it’s just the output that is trimmed.

However, the voltage value is a hard limit on the input and excess can (will?) damage the controller, even 0.1V over.

[CaptainRivet]

Originally Posted by sailingharry

So, some random responses to a lot of posts. It's long, apologies.



First, a really interesting tidbit on the size of the MPPT. Victron has a calculator. You put in all kinds of information about your panels, series/parallel, all the tech specs. It suggests a MPPT controller. I even picked the largest panel in the line that I was looking at, 380W. Two in P, and ran it as two in S. Victron recommends the 100/50. If you then go into the details, it specifically states that the solar array is 10% oversized for the recommended MPPT. So they are comfortable recommending a MPPT that will see throttling. The issue, I think, is that they recognize that a 10% loss for the small period of time that it occurs does not justify the next size up. Now, they didn't consider recommending splitting into two panels with two MPPTs. The next step up from the 100/50 ($300) is the 150/60 ($539). And there is a lot of discussion on the Victron forum of arrays that are sized for winter (low output) but 2-3 times the controller ability in the summer, with no issues.


There has been a lot of discussion on my budget. I never made it above middle management in my career, but am quite comfortable financially and have a comfortable retirement. I did this by ALWAYS considering financial implications. I can and do spend money. But I have never bought into the "this is one place you shouldn't skimp" (which is recommended in almost any conversation....LOL).


Rivet suggested I should oversize because I'm already regretting my choice of to buy the two 75/15, and reuse the existing 10A Genasun on my installation a mere 18 months ago. I'm not regretting! If I hadn't slid my boat into a concrete wall in 6 knots of current, requiring me to completely replace my arch and everything on it, I'd be happily using what I installed for a decade to come. But since I'm getting a new arch built, I have a lot of choices. And one of them is to make changes. But if I simply upgrade the one small panel (limited by something that is changing), and upgrade its controller accordingly, I'll have 600W in three fully independent systems, for a mere $300 out of pocket. Or I can, as I'm considering, push it to 730W (a whole 130W of power!) for a bit more. I still don't really know if 3 independent panels will avoid the backstay better (and provide more power) than two larger panels. I think the odds are high that one of 3 will always work -- and also high that certain sun angles will mostly kill two larger panels from backstay shading (but that may be an unusual event). With two panels, I can go a single 100/50, for $100 more I can go 2 100/30, and for another $200 more (a total of $300 more than a single 100/50 that is a 95% solution) I can go with two 100/50's. If I go from 3 panels to 2, the choice is a single 100/50 or two 100/30s -- two 100/50's don't meet the value threshold.



I currently have AGM. As pointed out by some, this will suck down almost anything my solar array can provide. I can routinely put over 50A (or 650W) into my AGM up to a bit over 90% SOC. Since I rarely get over 90% SOC, an LFPL won't take any more power than an AGM. However, I'm also intending to build an LFP bank this winter. As Noelex has pointed out, LFP will virtually eliminate the issue with the MPPT capacity. At 3.2V/cell (sort of a low-but-not-out value), an LFP will sit at 12.8V. At 50A output, a 100/50 can support 640W before it even begins to throttle. Although with my 740Ah AGM bank and modest loads, I rarely see a battery voltage below about 12.2 (I rarely hit my 3KW inverter with more than a toaster, and my windlass at 1kW or so only hits it for minutes at a time). And as Noelex points out, these momentary drops in voltage truly won't hurt the MPPTs. So in the morning, before voltage starts to come up, a 50A controller can support 610W.



Rivet keeps harping on half-cut bifacials. I'm intrigued. I'm having two issues -- cost (they seem about double single monofacial) and size -- I'm trying to maximize my capacity within my area. Solar vendors do a really good job of obscuring size -- they love to give lots of other specs, but size requires opening the listing, finding the size, realize they don't fit, lather-rinse-repeat. GRRR. I really want to keep my panels under 70" long and 41" wide.


Rivet has also commented that at peak sun, when the batteries are starting to reach full, he has lots of high power uses to put the energy to. We don't have as much flexibility. Our water maker (in 4 years of ownership and 8000 miles of cruising, I tested it and re-pickled it) is a low power 12V unit that doesn't draw much. Since we tend to move daily, our hot water is almost always hot from the engine. We cook on propane (and when we use our electric coffee pot and toaster, we don't have surplus sun!). So excess solar, which happens VERY rarely, is just...excess.

Thats a whole lot more information how your system looks and how you use it.

640Ah AGM won't limit 60A charge, you have no high loads to burn more off sensefully.
My buddy boat i mentioned is a Dufour 44 with performance rod rigg and he has also the same "backstay problem" then you do. And he replaced 3x160W Victron with one 365W Longli bifacial (the backstay is above the panel) and has more output then all 3 together before. Peak power is about the same but WH per day is 25% more then 3x160W panels.
The backstay creates mostly a quite small line of shade on the panel and moves the whole day.
Thats exactly the reason i highly recommended 2x bifacial half cut cells. Half cut means you have more cells per sqm and a higher "shade resolution" as less cells are affected by this partial shade. You can compare this too the resolution of a screen the more cell=pixcels the higher is the shade resolution/ screen resolution.
2nd that shade is not a hard shade, its a steel rope of 6-10mm most likely and sun can pass it so its a partial shade for modern bifacial panels
A)This shade will never take this panel out due to shading of the backstay is a small line partial shade, it will reduce its performance a bit by around 30-60W as it shades one row of half cut waver, less then if you use normal size as it will shade more cells=more loss
B) The backside that produces up to 25% additionally is never affected
C) these panels work with diffusion light means on passage you see much more production then with conventional panels and as backstay is only a 6-10 rope diffusion light gets around it and on the direct shaded cells, means the partially shade cells get diffusion light and so they produce energy and not going to 0 and block the whole row=more ouput
D) one of the panels is always not shaded by the backstay and produce 100%, the 2nd is a bit shaded and reduced to 85-90%, the total output in reality will be bigger the 3x200W.

The Longli 365W bifacials i have are 170Euro=340Euro. Comparable 410W Longil conventional are 135Euro, so we are talking about 70Euro here, outrages markup for the best solution to your problem. The arch is how much 2000-4000Euro??? Look at the total cost of your solar system and Euro/$ per WH harvested daily especially in not so perfect conditions...like autum or spring.

Panel sizes are standards made for residential and solar farms and you build a new arch, make it so that standard size 72 or 144half cut cells panel (340-450W) fit, they are 165-175cm long and 100-110cm wide. These are the panels that get optimised for maximum efficency, not your low volume 200W panel sold as space solution problem.
That saves money as they are build in high volume and are widely avaliable which also makes it easier to replace them if the get damaged or stop working. That save a ton of money and hassle. And on an new arch its really no issue if they are 10cm wider and 15cm longer then your wish size...make it fit.

As you don't burn off solar energy, have AGM and the backstay will nearly always shade 1 panel and reduce its performance by 10-15% with the mentioned bifacials half cut cells the 2x 30/100 MPPT Victron Smart is the economical solution for you as that bit 1 controller might deliver for a short periode of time with AGM not justify the upgrade cost to 2 50/100. Don't skip the upgrade cost to smart as this allows you to join both panels and the 2 MPPT synchronize.

[GreenWave]

Originally Posted by s/v Jedi

You have misinterpreted it. MPPT does not pass amps at all, nor does it pass voltage. You must look at it as passing energy.

If you have a panel that outputs 375W and your batteries absorption voltage is 14.4V then the amps going out is 375 / 14.4 = 26A. A 100/30 MPPT can -output- a maximum of 30A so it’s good.

The number for voltage is the Voc of the panels. If putting panels in series this comes into play. Also, the panels themselves have a maximum “system” voltage which is about wiring- and construction insulation rating and diode ratings.

The Victron regulators automatically limit and de-rate themselves so you can use controllers that are too small to pass available array power… you simply let some power go to waste. Shameful but technically allowed

My recommendation for the larger controller is for a list of reasons including easier future upgrades, possibly bifacial panels (up to 30% extra output) and reserve capacity in case another controller fails.

So, let me pose this situation that I am currently experiencing. Couple of weeks ago went to boat and found that there was ZERO amps being put into battery from our Solar Controller (a Blue Sky 3000i unit where I would often see 16-20 amps at high noon). After several resets and talking to Blue Sky, we determined that the controller was dead. So bought a Victron 100/50 Solar and installed it. I then saw that my panel output was very low. I have two- 250W Kyocera panels that were installed on arch in 2015. They are wired in parallel. Anyways, I have done several measurements on the panels individually, combined, with and without sun exposure and the current measured from them has never been higher than about 5A. the Voc is within 5% of panel spec. So are my panels also toast? I think so.


Any thoughts?

[CaptainRivet]

Originally Posted by sailingharry

So, some random responses to a lot of posts. It's long, apologies.



First, a really interesting tidbit on the size of the MPPT. Victron has a calculator. You put in all kinds of information about your panels, series/parallel, all the tech specs. It suggests a MPPT controller. I even picked the largest panel in the line that I was looking at, 380W. Two in P, and ran it as two in S. Victron recommends the 100/50. If you then go into the details, it specifically states that the solar array is 10% oversized for the recommended MPPT. So they are comfortable recommending a MPPT that will see throttling. The issue, I think, is that they recognize that a 10% loss for the small period of time that it occurs does not justify the next size up. Now, they didn't consider recommending splitting into two panels with two MPPTs. The next step up from the 100/50 ($300) is the 150/60 ($539). And there is a lot of discussion on the Victron forum of arrays that are sized for winter (low output) but 2-3 times the controller ability in the summer, with no issues.


There has been a lot of discussion on my budget. I never made it above middle management in my career, but am quite comfortable financially and have a comfortable retirement. I did this by ALWAYS considering financial implications. I can and do spend money. But I have never bought into the "this is one place you shouldn't skimp" (which is recommended in almost any conversation....LOL).


Rivet suggested I should oversize because I'm already regretting my choice of to buy the two 75/15, and reuse the existing 10A Genasun on my installation a mere 18 months ago. I'm not regretting! If I hadn't slid my boat into a concrete wall in 6 knots of current, requiring me to completely replace my arch and everything on it, I'd be happily using what I installed for a decade to come. But since I'm getting a new arch built, I have a lot of choices. And one of them is to make changes. But if I simply upgrade the one small panel (limited by something that is changing), and upgrade its controller accordingly, I'll have 600W in three fully independent systems, for a mere $300 out of pocket. Or I can, as I'm considering, push it to 730W (a whole 130W of power!) for a bit more. I still don't really know if 3 independent panels will avoid the backstay better (and provide more power) than two larger panels. I think the odds are high that one of 3 will always work -- and also high that certain sun angles will mostly kill two larger panels from backstay shading (but that may be an unusual event). With two panels, I can go a single 100/50, for $100 more I can go 2 100/30, and for another $200 more (a total of $300 more than a single 100/50 that is a 95% solution) I can go with two 100/50's. If I go from 3 panels to 2, the choice is a single 100/50 or two 100/30s -- two 100/50's don't meet the value threshold.



I currently have AGM. As pointed out by some, this will suck down almost anything my solar array can provide. I can routinely put over 50A (or 650W) into my AGM up to a bit over 90% SOC. Since I rarely get over 90% SOC, an LFPL won't take any more power than an AGM. However, I'm also intending to build an LFP bank this winter. As Noelex has pointed out, LFP will virtually eliminate the issue with the MPPT capacity. At 3.2V/cell (sort of a low-but-not-out value), an LFP will sit at 12.8V. At 50A output, a 100/50 can support 640W before it even begins to throttle. Although with my 740Ah AGM bank and modest loads, I rarely see a battery voltage below about 12.2 (I rarely hit my 3KW inverter with more than a toaster, and my windlass at 1kW or so only hits it for minutes at a time). And as Noelex points out, these momentary drops in voltage truly won't hurt the MPPTs. So in the morning, before voltage starts to come up, a 50A controller can support 610W.



Rivet keeps harping on half-cut bifacials. I'm intrigued. I'm having two issues -- cost (they seem about double single monofacial) and size -- I'm trying to maximize my capacity within my area. Solar vendors do a really good job of obscuring size -- they love to give lots of other specs, but size requires opening the listing, finding the size, realize they don't fit, lather-rinse-repeat. GRRR. I really want to keep my panels under 70" long and 41" wide.


Rivet has also commented that at peak sun, when the batteries are starting to reach full, he has lots of high power uses to put the energy to. We don't have as much flexibility. Our water maker (in 4 years of ownership and 8000 miles of cruising, I tested it and re-pickled it) is a low power 12V unit that doesn't draw much. Since we tend to move daily, our hot water is almost always hot from the engine. We cook on propane (and when we use our electric coffee pot and toaster, we don't have surplus sun!). So excess solar, which happens VERY rarely, is just...excess.

Thats a whole lot more information how your system looks and how you use it. So now we can give you proper advise for the best solution.

640Ah AGM won't limit 60A charge, you have no high loads to burn more off sensefully means top end production you take what you get but optimsation makes no sense economically.

My buddy boat i mentioned is a Dufour 44 with performance rod rigg and he has also the same "backstay problem" then you do. I went with this boat over the atlantic in january/Feb this year and helped him to reinstall the whole electric system and installed his 560AH of lithium bank. So i know it well. And he replaced 3x160W Victron with one 365W Longli bifacial (the backstay is above the panel) and has more output then all 3 together before. Peak power is about the same but WH per day is 25% more then 3x160W panels approx 6-8 years old.
The backstay creates mostly a quite small line of shade on the panel and moves the whole day.
Thats exactly the reason i highly recommended 2x bifacial half cut cells. Half cut means you have more cells per sqm and a higher "shade resolution" as less cells are affected by this partial shade. You can compare this too the resolution of a screen the more cell=pixcels the higher is the shade resolution/ screen resolution.
2nd that shade is not a hard shade, its a steel rope of 6-10mm most likely and sun can pass it so its a partial shade for modern bifacial panels
A)This shade will never take this panel out due to shading of the backstay is a small line partial shade, it will reduce its performance a bit by around 30-60W as it shades one row of half cut waver, less then if you use normal size as it will shade more cells=more loss
B) The backside that produces up to 25% additionally is never affected
C) these panels work with diffusion light means on passage you see much more production then with conventional panels and as backstay is only a 6-10 rope diffusion light gets around it and on the direct shaded cells, means the partially shade cells get diffusion light and so they produce energy and not going to 0 and block the whole row=more ouput
D) one of the panels is always not shaded by the backstay and produce 100%, the 2nd is a bit shaded and reduced to 85-90%, the total output in reality will be bigger the 3x200W.

The Longli 365W bifacials i have are 170Euro=340Euro. Comparable 410W Longil conventional are 135Euro, so we are talking about 70Euro here, outrages markup for the best solution to your problem. The arch is how much 2000-4000Euro??? Look at the total cost of your solar system and Euro/$ per WH harvested daily especially in not so perfect conditions...like autum or spring.

As you don't burn off solar energy, have AGM and the backstay will nearly always shade 1 panel and reduce its performance by 10-15% with the mentioned bifacials half cut cells the 2x 30/100 MPPT Victron Smart is the economical solution for you as that bit 1 controller might deliver for a short periode of time with AGM not justify the upgrade cost to 2 50/100. Don't skip the upgrade cost to smart as this allows you to join both panels and the 2 MPPT synchronize.

[CaptainRivet]

Originally Posted by GreenWave

So, let me pose this situation that I am currently experiencing. Couple of weeks ago went to boat and found that there was ZERO amps being put into battery from our Solar Controller (a Blue Sky 3000i unit where I would often see 16-20 amps at high noon). After several resets and talking to Blue Sky, we determined that the controller was dead. So bought a Victron 100/50 Solar and installed it. I then saw that my panel output was very low. I have two- 250W Kyocera panels that were installed on arch in 2015. They are wired in parallel. Anyways, I have done several measurements on the panels individually, combined, with and without sun exposure and the current measured from them has never been higher than about 5A. the Voc is within 5% of panel spec. So are my panels also toast? I think so.


Any thoughts?

Connect 1 panel with wires "free air" directly to the controller to exclude a cabling problem.
if you see then low output with full sun exposure your panel is toast, most likely the bypass diodes.