Biggest Solar Panels...

[s/v Jedi]

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?

Inconclusive. For each panel separately, note the current as well as the voltage at that same moment. Voc is meaningless for testing how much power comes out.

Also, give us the panel specs or post a picture of its label.

[Statistical]

Before going further test the amperage of the panel in short circuit (Isc) and compare to the specs. To do that you need a multimeter, set it up to measure current (may need to move the positive probe to current port). Disconnect the panel from everything else and connect multimeter to the + and - leads on the panels.



SAFETY: Check the max amperage of your multimeter vs the Isc of the panel. Most multimeters are at least 10A using the current port and many panels are under 10A Isc so it shouldn't be an issue but verify before checking unless you want to destroy your multimeter too.

If the panel (in isolation measured directly at the panel leads) in good sunlight (bright day near noon no shadows) has an Isc significantly lower (say 70% or less) than the rated isc then the issue is in the panel itself. Hopefully just bad bypass diodes.

Most panels have a junction box on the back to access the diodes. Unless the manufacturer hates you the box is just held closed by clips or screws. You can verify it is a bad diode with a multimeter. Likewise with decent soldering skills you can replace the diodes. Likewise from within the box you can reverify VoC and Isc to eliminate the panel leads as an issue. If it is anything other than the diodes or cabling it is likely not repairable.

If the Voc and Isc of the panel in isolation are both good well the issue isn't the panel. It is somewhere else.

[sailingharry]

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.

I believe that an MPPT does the translation by means of a "charge pump." I think that it has an electronic bucket that collects electrons at the high side and then lines them up at the low side and pushes them out. My understanding is that this is a very high efficiency conversion mechanism. My degree is mechanical engineering not electrical, so don't ask me to further explain my limited understanding! But taking that analogy, and then adding in a driver that runs it at a fixed speed, and you have something that is very analogous to a positive displacement pump. If you keep adding water to the pump at an ever increasing flow rate, the pump will remove all of it -- until the incoming water exceeds the capacity of the pump. Then it just continues to move at its maximum speed.

So as the analogy then applies to the MPPT, at a low power (electron flow rate), the controller happily moves every electronic gets. But when there are more electrons than fit in the bucket, they are just left in the queue. The controller does not make a conscious decision to throttle the power, and it does not overheat due to I2R losses or anything of that nature.

Hopefully, Jedi will either say "yep, that's sort of like it's done” or dissuade me of my erroneous belief. LOL

[sailingharry]

Originally Posted by fxykty

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.

I understand that the voltage limit can lead to some confusion. Much of the time, the panels run at Vmp, and that is what people look at because that is where their panels are often running.

The problem comes when the batteries reach 100%. At that point, the controller stops passing energy and basically becomes an open circuit. And suddenly the panels are at Voc. This is further complicated as I have recently learned by the fact that Voc has a strong temperature factor. At very low temperatures, like midwinter (coincidentally a time when many boats are not consuming much electricity, so the controller is likely have "shut off"), Voc can be considerably higher than the value listed on the spec sheet.

[GreenWave]

Originally Posted by Statistical

Before going further test the amperage of the panel in short circuit (Isc) and compare to the specs. To do that you need a multimeter, set it up to measure current (may need to move the positive probe to current port). Disconnect the panel from everything else and connect multimeter to the + and - leads on the panels.



SAFETY: Check the max amperage of your multimeter vs the Isc of the panel. Most multimeters are at least 10A using the current port and many panels are under 10A Isc so it shouldn't be an issue but verify before checking unless you want to destroy your multimeter too.

If the panel (in isolation measured directly at the panel leads) in good sunlight (bright day near noon no shadows) has an Isc significantly lower (say 70% or less) than the rated isc then the issue is in the panel itself. Hopefully just bad bypass diodes.

Most panels have a junction box on the back to access the diodes. Unless the manufacturer hates you the box is just held closed by clips or screws. You can verify it is a bad diode with a multimeter. Likewise with decent soldering skills you can replace the diodes. Likewise from within the box you can reverify VoC and Isc to eliminate the panel leads as an issue. If it is anything other than the diodes or cabling it is likely not repairable.

If the Voc and Isc of the panel in isolation are both good well the issue isn't the panel. It is somewhere else.

Yep I have made all of these measurements. Here is the full rundown. First the panel specs. Voc = 36.9, Isc = 9.09A, Vpm = 29.8 Ipm = 8.39.



My measurements on the panels are:
Port Panel, uncovered and isolated from other panel/controller
Voc = 30.8
Amps = 3.3 (measured with meter inline between the two MC4 connectors)

Stbd Panel -
Voc = 30.72
Amps = 3.3
Same values covered, respectively are:

24.1 V, 4.32 A; 23.5V, 2.76A
Then when combined in parallel, and meaured again uncovered (not yet connected to controller)
Voltage = 34.25, Amps = 5.91


Let me know if I am missing some measurement and what you guys think.

[CaptainRivet]

Originally Posted by GreenWave

Yep I have made all of these measurements. Here is the full rundown. First the panel specs. Voc = 36.9, Isc = 9.09A, Vpm = 29.8 Ipm = 8.39.



My measurements on the panels are:
Port Panel, uncovered and isolated from other panel/controller
Voc = 30.8
Amps = 3.3 (measured with meter inline between the two MC4 connectors)

Stbd Panel -
Voc = 30.72
Amps = 3.3
Same values covered, respectively are:

24.1 V, 4.32 A; 23.5V, 2.76A
Then when combined in parallel, and meaured again uncovered (not yet connected to controller)
Voltage = 34.25, Amps = 5.91


Let me know if I am missing some measurement and what you guys think.

Issue within panel, assume bypass diodes are toast. Your ISC is 2,76A which is 30% and should be above 8A when you measure when panel is ok.

[GreenWave]

Originally Posted by CaptainRivet

Issue within panel, assume bypass diodes are toast. Your ISC is 2,76A which is 30% and should be above 8A when you measure when panel is ok.

Yep- that makes sense. Will see if I can get inside the junction box and test the diodes and remove them. Then will go from there. Removing and replacing the diodes may be easier than replacing the panels and certainly much less $$$.

[noelex 77]

Originally Posted by GreenWave

Yep- that makes sense. Will see if I can get inside the junction box and test the diodes and remove them. Then will go from there. Removing and replacing the diodes may be easier than replacing the panels and certainly much less $$$.

If those measurements were taken in full sun (with the sun reasonably close to directly overhead) then the panels are performing poorly and should be replaced.

The bypass diodes are always worth checking, but I doubt they are the problem in this case.

The diodes normally fail in two ways. If they fail open circuit there will be no change in the output with no shade. If they fail short circuited you will lose 1/3 of the Voc (assuming three bypass diodes) and your voltage is well above this.

[sailingharry]

So upthread I injected my "largest solar panel" issues, along with desires to control size and cost. Since then, I've done about 1000 hours of research, and fought 3 rounds with my arch builder (I've decided the way to solve the Admiral's concern is to ignore it -- I've not ignored her concern, but I'm not discussing it with her.)


First, a small rant. Solar vendors all over list all sorts of data up front -- useless stuff like efficiency. The ONLY way to get dimensions is to download and open the spec sheet. GRRR.... and like vendors of all over, it gives sort options like "price" and "newset" and "most popular" but not useful stuff like "W" or "Length." Rant over.....LOL


So I have settled on a pair of 400W bifacial. They are a few inches longer than my existing, but most of the upgrade is in width, which is good. Energy density is 202W/M2, which is pretty much spot on the "reality check" value. Just shy of $700, which ain't cheap, but despite some of the impressions in my earlier post, price is a concern but not a primary concern.



So now I need to look at a pair of controllers. My Victron rep is a very knowledgeable fellow who has the same boat (Saga 43), lives aboard full time, has upgraded to 24V, talks KWh instead of Ah, has shifted to 100% electric cooking, and is contemplating a conversion to Diesel/Electric hybrid (OK, that's a downcheck in credibility, at least in my book). He says I'm not going to get value from the 100/50, go with 100/30.


Here's the math.
400W/30A = 13.3V. That means that at full solar power, I don't clip if my batter is over 13.3V.
With 10% Bifacial Gain, 440W/30A = 14.6.


What are real-world charging voltages on an LFP pack? I know you don't get the over-pressure that you do on a AGM, where you charge at 14.6 or so when the resting voltage is more like 13.2 (or even 13). But you do get some overpressure. Also, you have 4 hours of charge behind you when that noon hour shows up to give you 440W, so volts have come up.


It seems to me that if I'm up to 70% SOC or more, resting voltage is right around 13. That makes the 13.3V to get full rated power (400W) exceptionally reasonable. It also says that if I can get the full rated power (400W) at high noon, then I'm missing the "bifacial kicker" of about 40W, or 3A, for about an hour (the bifacial boost is fully useable when not getting noon sun). Meaning, I'm leaving 3Ah per panel, or 6Ah per day, on the table. Makes my Victron rep sound pretty smart. $200 in controllers to get 6Ah/day in summer sun.


So, the question. I've never even touched an LFP battery, let alone used one. What are real-world battery voltages under heavy solar charging rates? At 13V, I'll go 100/50, but at 14V, I'll go 100/30...in between I'll flip a coin. (My intended pack will be about 600Ah, so I'm looking at solar charge rates of .1C, maybe net .07C after house loads)

[noelex 77]

The extra energy that will be harvested from the larger controller is going to be quite small. In a good solar system the panels should be occasionally delivering their full rated power. An output even higher than this rating is not unusual, but this will for very brief periods. These high outputs are an important indication that the system is healthy, but they do not contribute much to the overall energy harvest.

There are a couple of other points to consider:

1. The Victron controllers run quite hot. There is only passive cooling. A larger unit with its larger heatsink will run cooler. The smaller controller is dependent on its self protection mechanism, limiting the current to 30A. A larger unit is not dependent on this mechanism working correctly. For both of these reasons the larger unit is likely to be more reliable.

2. If one unit does fail, then both panels can be connected to one controller. The larger unit will deliver close to the normal output adding valuable redundancy.

3. If more efficient panels become available in the future you can upgrade without changing the controller.

To answer your specific question about "charging" voltage is not simple. Often when solar power is at its maximum, this is the time when heavy loads are run. The battery may even be discharging despite the solar panels delivering their full output.

[GreenWave]

Originally Posted by sailingharry

So upthread I injected my "largest solar panel" issues, along with desires to control size and cost. Since then, I've done about 1000 hours of research, and fought 3 rounds with my arch builder (I've decided the way to solve the Admiral's concern is to ignore it -- I've not ignored her concern, but I'm not discussing it with her.)


First, a small rant. Solar vendors all over list all sorts of data up front -- useless stuff like efficiency. The ONLY way to get dimensions is to download and open the spec sheet. GRRR.... and like vendors of all over, it gives sort options like "price" and "newset" and "most popular" but not useful stuff like "W" or "Length." Rant over.....LOL


So I have settled on a pair of 400W bifacial. They are a few inches longer than my existing, but most of the upgrade is in width, which is good. Energy density is 202W/M2, which is pretty much spot on the "reality check" value. Just shy of $700, which ain't cheap, but despite some of the impressions in my earlier post, price is a concern but not a primary concern.



So now I need to look at a pair of controllers. My Victron rep is a very knowledgeable fellow who has the same boat (Saga 43), lives aboard full time, has upgraded to 24V, talks KWh instead of Ah, has shifted to 100% electric cooking, and is contemplating a conversion to Diesel/Electric hybrid (OK, that's a downcheck in credibility, at least in my book). He says I'm not going to get value from the 100/50, go with 100/30.


Here's the math.
400W/30A = 13.3V. That means that at full solar power, I don't clip if my batter is over 13.3V.
With 10% Bifacial Gain, 440W/30A = 14.6.


What are real-world charging voltages on an LFP pack? I know you don't get the over-pressure that you do on a AGM, where you charge at 14.6 or so when the resting voltage is more like 13.2 (or even 13). But you do get some overpressure. Also, you have 4 hours of charge behind you when that noon hour shows up to give you 440W, so volts have come up.


It seems to me that if I'm up to 70% SOC or more, resting voltage is right around 13. That makes the 13.3V to get full rated power (400W) exceptionally reasonable. It also says that if I can get the full rated power (400W) at high noon, then I'm missing the "bifacial kicker" of about 40W, or 3A, for about an hour (the bifacial boost is fully useable when not getting noon sun). Meaning, I'm leaving 3Ah per panel, or 6Ah per day, on the table. Makes my Victron rep sound pretty smart. $200 in controllers to get 6Ah/day in summer sun.


So, the question. I've never even touched an LFP battery, let alone used one. What are real-world battery voltages under heavy solar charging rates? At 13V, I'll go 100/50, but at 14V, I'll go 100/30...in between I'll flip a coin. (My intended pack will be about 600Ah, so I'm looking at solar charge rates of .1C, maybe net .07C after house loads)

I have been running a 100/50 for about 6 weeks and love it. In early stages of a lithium battery upgrade. I would suggest that if you have plans for lithium in the near future then go with the larger controller.

[RedneckRedcoat]

I have three 410w bifacial running two in Parallel to one controller and the third into a separate controller.

With 3 x 100ah BB Lithium we are fully charged by lunch time on a good day. You want to be charging as close to the batteries specification which you should get from the manufacture.

I’d get the 100/50 as you can run them up to 100v on the voltage from your panels and get up to 50 amps out

[sailingharry]

Originally Posted by noelex 77

The extra energy that will be harvested from the larger controller is going to be quite small. In a good solar system the panels should be occasionally delivering their full rated power. An output even higher than this rating is not unusual, but this will for very brief periods. These high outputs are an important indication that the system is healthy, but they do not contribute much to the overall energy harvest.

There are a couple of other points to consider:

1. The Victron controllers run quite hot. There is only passive cooling. A larger unit with its larger heatsink will run cooler. The smaller controller is dependent on its self protection mechanism, limiting the current to 30A. A larger unit is not dependent on this mechanism working correctly. For both of these reasons the larger unit is likely to be more reliable.
.

This is an interesting point. Be curious if anybody has done a side-by-side comparison between the 100/30 and the 100/50. I ask this because the physical dimensions of the two units are identical. I know that plastic is cheap and heat sinks not so cheap, but there is a pretty good chance that if the physical dimensions are the same, the heat sink is the same. Anybody have one of each someplace easy to look?

[rslifkin]

I only have the 100/30s on my boat, but even under a decent load, I've never found them to get more than somewhat warm. Not nearly as hot as I hear of with some of the smaller Victron controllers.

[noelex 77]

Originally Posted by sailingharry

I know that plastic is cheap and heat sinks not so cheap, but there is a pretty good chance that if the physical dimensions are the same, the heat sink is the same. Anybody have one of each someplace easy to look?

You’re right. The 100/30 and 100/50 look to have the same heatsink.

This is not true of other models, for example the 100/20 has a much larger heatsink than the 75/15.

I assume Victron are trying to standardise components to achieve some economies of scale. This means the heatsink size for 100/30 was larger than strictly needed, which should help it run cooler than some of the other solar controllers in the range. Rslifkin’s experience seems to confirm this.