Degree of over paneling supported

This question is for Tech Support.

I understand that over paneling is supported on the AC200P and on the charging enhancer (D050S). Over paneling come in handy during the winter when there is less light.

Before I buy rigid panels, and install a Ground Mount, I want to be sure they do not exceed the specs of the two charge controllers.

The specs on the website and the manuals are sparse.

For the AC200P the manual says, “ Solar Input 35v-150v, 12A max, and 700W max (only 12A will be received when the current exceeds 12A).”

For the D050S Charging Enhancer it says, “12-60v, 10A max, and 500W max.”

These data are insufficient to make decisions about panels.

I had to learn elsewhere that the “charging enhancer” is a MPPT controller (voltage regulator) – this was not in the manual.

MPPT controllers vary widely in the degree of over paneling they support and some in the maximum Isc they can handle. None of this information is in the specs available. I do not want to just wing it and guess at what it can handle without issues. It is too expensive to make mistakes. For over paneling, some MPPTs can handle 8%, some 50%, some 100%, some more. While a few have very strict limits on max Isc coming from the panels. Excessive over paneling can cause over heating of a controller. Exceeding the max Isc can burn out a controller.

I would like to use 3 each 120-cell 365W in series for the solar input.

total 1095W (64% over paneling)

Impp 10.65a

Isc 11.32a ,

34.2 Vmpp

40.8Voc,

Total Voc of 139v for 3 panels calculated to compensate for temperature variation for this specific panel.

I would like to use 1 each of these same panels for the charging enhancer.

Total 46.33Voc after temperature compensation.

34.2 Vmpp

Impp 10.65a

Isc 11.32a ,

The voltage looks good, my question is on the amps (max Isc from panels allowed), and on the over paneling (highest % supported).

Without knowing the internal specs, I cannot decide if these will work or not, so I need the help of tech support. The AC200P is a beautiful unit but does me no good without know if these panels will work. I have not bought the panels yet.

I would be a big help not only to me but to others to know what percent of over paneling is supported and what Isc coming from the panels should not be exceeded, including safety factors, for each of the two controllers.

I look forward to a definitive response, so I do not screw this up. Thanks so much.

2 Likes

In my personal opinion, a manufacturer is not going to state any specs other than the max allowed input. All specs have a little wiggle room, but it would be a liability issue to state an amount you can exceed without having a safety issue. That would be kind of like buying a small truck with a cargo capacity of 1,000 lbs and wanting the Mfg. to state how many extra lbs you can actually haul before the axle breaks or the breaks do not remain safe.

2 Likes

@SteveG,

From how i understand it, the amps are not an issue (in the same way VOC is) as the bluetti unit (AC200P in your case) will just limit it to the max it can support (so 12 amps(AC200P) or 10 amps(D050S in your example).

I suppose if you had a huge array and were pushing in so much power you could get overheating issues? Maybe buy one solar panel less to begin with and see how it goes from there, or to put it another way start smaller (in relation to the solar arrays) and build it up as you get the system running well.

1 Like

@CK0Co2 @ Scott-Benson

Thank you.

This is not a matter of liability, but of how to use the product safely without issues by knowing what the specs are. If you buy a picture hook in the store, it tells you not to exceed 5 pounds, or 10 pounds, or 50 pounds so you know which painting you can hang on which.

I have made a chart below of the specs and what is missing.

Yes, Voc is critical, but amps and panel wattage are important as well.

If you look up the specs on any MPPT controller, they always tell you the “ max rated charging ” output values and the “ max PV short circuit current” input values. Or they will tell you the “ rated PV power ” input and the “ maximum PV power ” input.

The difference between the two is the amount designed into the system to allow for safe over paneling. Above this amount excessive heat can be generated, or it can increase the open-circuit voltage of PV array. The designer intentionally determines the degree of over paneling by the specs of the components and the design of the container. Some MPPT controller designs allow no over paneling, others allow 8% or 20% or 50% or 100% or more. Generally, regardless of whether the controller allows it, going over 50% over paneling yields diminishing returns.

In any event you cannot guess at it. You need to know the design specs.

It should be obvious that if you over panel by 50% but the controller was designed for 8% you are going to get early failure of your equipment. On the other hand, if it allows 100% over paneling and you do none, you will get diminished charging in winter - extending charging time. Also, remember you rarely get the rated wattage out of a panel, except under ideal conditions. So, there is a balance.

Victron

For example, the Victron 100/30 MPPT controller documentation states “rated charge current” is 30A and the max “PV short circuit current” is 35A. This means it will charge at a max of 30a, but you can input 35a safely, meaning a 20% maximum over paneling is built into the design.

Epever

Another example, the manual for the Epever Tracer XTRA3415N with a “rated charge current” of 30A says, “The maximum power of PV array shall be not greater than 1.5 x the rated charging power of controller.” And it gives the following 50% over paneling recommendations for this 30A charger:

Rated Charge Power Max PV Array Power

390w/12V 580w/12V

780/24v 1170w/24V

1170W/36v 1755W/36W

1560W/48v 2340W/48v

Bluetti

The specs for Bluetti, on the other hand, are confusing.

I made up a summary chart of the Bluetti specs to help my friend Paul decide which Bluetti he wants, if any. He is leaning towards the E300 but will not decide until we get a better handle on the missing specs to determine which panels to use, the important panel specs being Isc and Voc, and the missing Bluetti specs being the “max PV Isc.” Amps are stated in the Bluetti manuals, but it many instances it does not say if this is the “max rated charging current” or the “max PV Isc.” That is like saying the speed is 50 but not telling you if it is feet per second or mile per hour.

The only one with complete specs is the D050S Charging Enhancer. It clearly states the Isc is 10A.

I have put question marks where important data are missing.

From these specs, the only Bluetti panel that will work with the charging enhancer is the PV100 at 24.4Voc and 6.43A. The total Voc for 2 panels, plus an approximate 5% temperature correction factor, is 51.24v. For three panels it is 76.9Voc, so 3 panels will not work. Thus, with the Bluetti panels, the maximum that can be used are 2 each 100W panels on the “500W” charging enhancer.

The PV200 and PV350 will not work safely with this charging enhancer per the Bluetti specs of Isc 10.3A and 10.8A respectively.

Furthermore, most of the standard 60-cell/120-cell, 72-cell/144-cell rigid panels will not work with it either. Most exceed 10A – and the others are right on the edge at 9.82A. I do not want to mix panel sizes on my array, so this enhancer is kind of useless to me and I will return it. It is under powered and not worth the expense and trouble for just 200 watts.

Yes, some people are saying they are using more watts and more amps and they are okay. I say, yes, okay for now. But you are voiding your warranty and stressing your equipment beyond the specs so your equipment will die an early death.

These specs also say the AC200P “input max power” is 700W. Provided the person that wrote the specs was an engineer and knew what they were doing, means it cannot be over paneled beyond 700W safely without voiding the warranty and stressing the equipment.

BottomLine

  • Need clarity on the Bluetti specs, especially max Isc panel input and max panel wattage input to the Bluetti. In many cases it just says watts or amps not saying if this is max charging or max input.
  • The charge enhancer is too under powered, and I canceled my order.
  • I like my AC200P it is running well. It is a bit underpowered for handling panels but at the price, it is a good unit. I have found a couple of 350W rigid panels that are compatible with the AC200P specs but the shipping cost is outrageous, or in some cases, they will only ship you a bundle of 10 panels. No one locally sells panels. Only the installers have panels and they do not sell them.
  • I realize Bluetti is a young company and glitches, like the lack of clarity in the specs, are to be expected now and then. Hopefully, these will clear up as time goes on.
  • Overall I researched 16 manufacturers and like Bluetti the best.

Is there any way we can get the missing data from the spec sheets? As a first approximation, I can posit that the currents shown are the “max PV Isc” and not the “max rated charging current,” but that will cut down the choices of panels available because many will exceed 12A. Half the panels in this size are 14A.

I think you may have better luck contacting Bluetti directly for the information desired. If you want a hard input number, the max input limit is already posted on each spec. And by the way, liability and safety go hand in hand. Nice looking chart and post by the way.

1 Like

I’m also interested about this same issue. I was actually about to order a few more panels than the maximum 700W (was thinking 900W) to make sure to make it as “efficient” as possible even on a more cloudy day lets say. I was only thinking max amps and volts so I’m glad you brought up this question!

2 Likes

I have four 200 watt panels hooked up to my AC200P. It runs 24/7 powering a small office setup. Computer, router etc. So far no problems.

1 Like

Ok, great info, thanks! :slight_smile:

Rigid Solar Panels – Source, 60-cell vs 120-cell vs 72 cell vs 144-cell

I was frustrated with finding any source of standard-sized rigid solar panels that did not cost $200 to $400 in shipping. Fortunately, I finally found a great source. They are national and have 70+ locations around the USA and with free shipping or pickup within each State - CED Greentech, https://www.cedgreentech.com/locations.

From Greentech, I bought 2 each, new, top brand, 120-cell solar panels for $224 each.

Q Cells Q.Peak-DUO-BLK-G8+_Black 340W, 40.95 Voc, 10.45 Isc

Q Cells is in the top 5 in reliability worldwide.

60-cell and 120-cell solar panels are the same size but 120-cell (called half-cells) have many advantages over 60-cell – for a comparison see, Are Half Cut Cell Solar Panels Better Than Standard Panels?.

60-cell and 72-cell, and their corresponding 120-cell and 144-cell configuration, are the standard sizes for solar installations. Half-cell panels have two junction boxes instead of one - increasing reliability. They connect the same way as 60-cell panels.

Here is some more information on standard rigid-panel sizes:

The link on this comment froze my computer and made it unresponsive. I recommend NO ONE click on it as it seems to be navigating to a malware site.

Hi Birvin,

I am sorry you are having issues with your PC. As the owner of a computer repair company I can assure you these links are good. You may have some redirecting malware on your PC or other issues. I suggest downloading the free Malwarebytes software and running a scan to clean your PC. Also, bad RAM can cause random freezes on your computer. First try reseating your RAM, then use Memtest86+ to test your RAM. Run Memtest86+ overnight to see is your RAM is okay. I hope this helps. -SteveG

I am a software developer and am A+ certified in hardware. Thanks

Bryan Irvin
Full Stack Developer

Retired electrical engineer here. The only thing that should cause damage is over voltage. Over amperage is perfectly safe as the controller will simply stop drawing power.

Let’s consider the AC200MAX. Here are the solar input specifications:

900W Max., VOC 10-145VDC, 15A

We want to be very sure we keep the input voltage below 145VDC!

Let’s say we want to add as many SP350s as possible. The SP350 has a max open circuit voltage of 42 volts. That means we can put three of them in series and still be safely below the maximum input voltage of the AC200MAX.

We can now add more SP350s in parallel as long as they are also in groups of three. For example, say I had 30 SP350s. I would wire up 10 groups of 3 each in series. I would then wire all ten groups in parallel. This should work safely with the AC200MAX.

In practice, what is going to happen here is the sun is going to come up, and our 10500 watts of panels is going to very quickly be generating enough energy that the AC200MAX will be drawing it’s 900 watt maximum. And it will stay at the 900 watt maximum until close to sunset.

So, why would we not do this? Because we just dropped $21,000 on solar panels to power a $2,000 battery. We would get far more energy if we split the money more evenly between batteries and solar panels.

In general, adding more panels than the equipment can harvest is called DC oversizing. If you take the nameplate DC capacity of the panels and divide by the maximum possible power harvested, that is called the DC oversize ratio. In solar applications, it is common to see that between 1.2 and 1.4 these days. Highest I’ve ever seen is 1.8. As solar PV gets cheaper, I expect DC over sizing will continue to increase.

3 Likes

MikeN, thanks for your post.

I completely agree with you (and others) who say that under normal conditions the current flowing in the solar-panel/MPPT-controller circuit is controlled by the MPPT, and it will protect itself from over-current damage.

However, the original poster has quoted several MPPT spec sheets that clearly impose a requirement on max short-circuit current (Isc). Other discussions on the web say that requirement exists because the reverse polarity protection system in the MMPT (some diodes across the solar panel connector?) will create a short circuit in a reverse polarity situation, allowing Isc to flow through certain parts of the controller. Can you confirm that reverse polarity protection systems in MMPT controllers do short-circuit the panels?
Thanks

Great thread and some great replies too. Despite being an EE myself, the lack of more detailed info, and even a decent description of the charging system operation, makes it hard to get the most out of my AC200P . First problem was on me, I didn’t do enough homework and would have never thought they’d sell a product that couldn’t run from a single panel, but it seems that wasn’t fixed until the max.

What is not clear (or not documented) is the current input. If we are going to get 700w when we can only charge at 12A, then we are going to need close to 60V, which means 5 panels standard 100W panels in series? And even then, only at max output. Surely the requirements can’t be that rigid. We need at least some DC-overdesign or over paneling unless we want to be well below 700w in all but peak hours.

This makes it really hard to choose panels. Too much guesswork.

My current mobile system would benefit from a 2 or 3 24v (max)( panels in series for for keeping me in the 48-72v volt range (and in most light, above my units 36V minimum charge voltage. Those panels can produce up to 18A, which is about 50% high. If that’s simply not used by whatever circuit the internal MPPT has, that’s fine. Sure would be nice to know.

I"m also looking at maybe 3 200W panels in series with Pmax of 17v and
Imax of 12.35 if need be (surely that’s not too much) but I’ll be under charging in all but peak sun

Anyone have any more thoughts? All input appreciated.

Thanks

For me it takes five 200w panels in series to get 700 watts into my AC200P. I’m using the Bluetti SP200’s.

On most systems, voltage is the key to getting close to the maximum input. Gotta get the volts up if you want max input. (Assuming you have sufficient panel wattage available)

To Landlocked’s point, I did some digging on what could go wrong with very high short circuit current. The biggest issue I found is simply the electric code forbids high short circuit currents. Specifically, NEC 690.8(A)(1) limits MPPT input to have short circuit current no higher than 25% more than maximum normal current input. Apparently, this was done for safety reasons. Even if everything works well under normal operation, the idea is to limit the amount of excess energy when things go wrong.

They amended the code to allow for greater ratios but only if an electrical engineer signs off and there has to be at least 100KW of PV. And I don’t think anyone setting up Bluetti gear is going to get close to that.

Interestingly, the MPPT makers clearly don’t like this. Fronius even has a letter that states their equipment is all perfectly fine with a short circuit current 50% higher than max current.

So now I am very curious, what exactly would happen with a huge number of panels in parallel?

I thinking wiring a quick blow fuse in line with the solar input would allow experiments in relative safety. That said, anytime one goes beyond the electric code, it is surely territory people should not enter lightly.

Hi Mike, what you can do is to put an inline PV fuse that is maximum 125% of the input. Then you would meet NEC code.

I wish I understood the concerns behind the NEC’s rule. If the MPPT generates a short across its PV input terminals then (I think) there are only two components that could catch fire: the wiring connecting PV and MPPT, and whatever component inside the MPPT is creating the short (reverse polarity circuit?).

Of course, the installer should provide appropriate fusing to protect every wiring segment against a hard short anywhere.

So, is the NEC worried about the MPPT catching fire in a reverse polarity situation?