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Connecting "too many" solar panels to an All-In-One

Coil

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I currently have 6 (2p3s) 320 watt panels with attached to an LV2424 Hybrid unit. The panels have an open circuit voltage of of 40v and current of 10 amps. This results in 120v at 20 amps going into the charge controller.

This unit itself has max PV input of 145v, max charging current of 80 amps, and max input power of [2000] watts so the above works just fine.

In general I get at most about 1400 watts out of the panels at peak (they are not an ideal facing but it's the best I can do on my property).

Now it just so happens that I have 3 other identical panels (they were on sale) that I have not installed anywhere.

If I expanded the array to 3p3s I would still be well within the voltage and current ratings of my LV2424 but I would be overshooting the power limit at times. My question is this: Would the charge controller simply not draw power in excess of 2000 watts in that situation?

Since currently if my battery is full and my loads are not using all of the power being generated the PV power input on the readout simply caps at whatever is actually able to be used. I'm just wondering if there is some other limitation that would make this a bad idea.
 
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max input power of 200 watts
I assume that is 2000W

Would the charge controller simply not draw power in excess of 2000 watts in that situation?

Yes. The SCC will just not take the excess power. Doing some quick math, if 6 panels get you 1400W peak then you are getting around 1400/1920 = .73 or 73% of the rated power (this is not an uncommon event). Assuming the trend holds, 9 panels will peak out at ~2100W of production so there is only about ~100W left on the table at the peak. However, by adding the panels, you will be generating more power earlier in the day and later in the afternoon. Furthermore, you will produce more power on cloudy days. Consequently, your overall production should increase nicely.

Note 1: If you have a combiner box at the panels and a long run to the inverter, you may need to upgrade the wire size to the panels to get the full benefit of the additional panels and maintain a safe installation.


Note 2, You have about 17% safety margine on the input voltage. That is probably fine if you don't have sub-zero temps, but if you live in a cold climate you may want to run a check on the voltage rise at the coldest you expect the panels to ever experience.
 
Yes. The SCC will just not take the excess power. Doing some quick math, if 6 panels get you 1400W peak then you are getting around 1400/1920 = .73 or 73% of the rated power (this is not an uncommon event). Assuming the trend holds, 9 panels will peak out at ~2100W of production so there is only about ~100W left on the table at the peak. However, by adding the panels, you will be generating more power earlier in the day and later in the afternoon. Furthermore, you will produce more power on cloudy days. Consequently, your overall production should increase nicely.
So if he expanded his array, is he technically not overshooting his max VOC and isn't that the big no-no? Are we assuming the same adjusted peak for the VOC as the 73% wattage he's seen? I have the LV2424s as well, I've had this similar question at times.
 
The OP is going from 2 parallel strings of 3 panels in series to 3 parallel strings of 3 panels in series. Since he is not adding anything in series, the Voc is the same for both configurations so he should be good.

BTW: Something I should have mentioned before. With 2 parallel strings, you don't have to fuse each string. However with 3 parallel strings you do.

 
always wondered what would fry a mppt sooner, too much voltage or to much amps
The amps flow because the MPPT dynamically creates a load. I would not buy a charger that was not smart enough to limit the current at its rating. Such a design would be super dumb in today's world of micro controllers (true for the paste 20 or 30 years).
 
The amps flow because the MPPT dynamically creates a load. I would not buy a charger that was not smart enough to limit the current at its rating. Such a design would be super dumb in today's world of micro controllers (true for the paste 20 or 30 years).
never came close to either,havent had the guts to do so as i love my inverters too much.
 
never came close to either,havent had the guts to do so as i love my inverters too much.
I put 2 (in series) 295w 60cell panels onto an EPEver Tracer 10amp unit, to a 26v battery. Those panels (maxed out) would/could deliver over 22amps to the battery. The charger pegged out just under10amps and just stayed like that until the sun went low. That is what you should expect. It would also be wise and easy that the charger would throttle back if the temp got high from poor ventilation or a high ambient temp. I don't know if anyone does that in their design but they should.
 
always wondered what would fry a mppt sooner, too much voltage or to much amps
Most (All?) modern mppt controllers only have a input limit on the voltage. The throttle the current to what they can handle. Consequently, as long as the voltage is below the limit, you can over-panel to your hearts desire.

Having said that.... I never underestimate the ability of equipment companies to do dumb things so it is always a good idea to check that this is true for your controller.
 
you all must have bigger "cohones" than i do, but good to know
I am actually quite risk averse in my designs. Some MPPT controllers actually document what I described above. (The Victron MPPT controllers all document this)

It turns out that when designing an MPPT circuit, it is a normal result that the power going through the controller will be controlled to what it can handle. However, since I don't know the internal design of the controllers, I look very closely at the documentation to find out what happens in an over-paneled-but-OK-voltage situation. If the documentation is not clear that it is OK, I would not do it without contacting the company and getting a clear statement.

Having said that, the behavior I described is so ubiquitous with MPPT controllers that a lot of people just assume it and over-panel the system. I have not heard of people having issues due to over-paneling their MPPT controllers so I have to assume it is the extreme exception that an MPPT controller can't be over-paneled.
 
I am actually quite risk averse in my designs. Some MPPT controllers actually document what I described above. (The Victron MPPT controllers all document this)

It turns out that when designing an MPPT circuit, it is a normal result that the power going through the controller will be controlled to what it can handle. However, since I don't know the internal design of the controllers, I look very closely at the documentation to find out what happens in an over-paneled-but-OK-voltage situation. If the documentation is not clear that it is OK, I would not do it without contacting the company and getting a clear statement.

Having said that, the behavior I described is so ubiquitous with MPPT controllers that a lot of people just assume it and over-panel the system. I have not heard of people having issues due to over-paneling their MPPT controllers so I have to assume it is the extreme exception that an MPPT controller can't be over-paneled.
so, you would say that on most mppt chargers i can over voltage, but should never over amp
 
so, you would say that on most mppt chargers i can over voltage, but should never over amp
NO!!!! I am saying that on most MPPT controllers, if you don't over-volt the input you can over panel as much as you want. The controller will automatically limit the current to what it can handle.

Think of it this way: There is no reasonable way for the MPPT controller to manage the voltage at it's inputs and if the voltage gets too high it will burn out electronics. However, the controller can easily limit the current flowing through itself. Consequently, on most MPPT controllers, it is not possible to 'over-current' them as long as you don't over-voltage them.
 
BTW: The same is not true with PWM controllers. Many of them do have an input current limit.
 
Most inverter controllers will specify a limit on total PV input they can manage. Stay well within the Voc and the total kW array limit and you'll be fine.

If the array can produce more current than the rating for the controller, the controller will simply clip current at/near the limit.

Here's an example - it's from a larger Fronius grid tied inverter but the principle is the same:

Screen Shot 2021-09-08 at 3.28.51 pm.png

There are two MPPT inputs, one with a higher current limit of ~25A, the other with a limit around 15A. Both have the same sized array connected, one with a different string orientation mix than the other.

Can see the current clipping one MPPT input for ~6 hours from about 9am to 3pm. This is normal during good solar production periods and is making efficient use of the inverter. Yep a bit of array production potential is lost but that's well and truly made up for when conditions are no so good.

Often such over panelling is done via split orientation (easterly and westerly facing) arrays in parallel which tends to keep total current down somewhat by spreading output over a longer period of the day.
 
so, you would say that on most mppt chargers i can over voltage, but should never over amp
This has been correctly stated already but it is sometimes misunderstood. So I will toss out some more words.

The max PV in is limited by the internal design's parts. If you want to design for max PV volts of 50v or max PV volts for 200v, many things will be different and more expensive for the 200v solution. For example a capacitor that can take 200v without an internal short will be larger and more expensive than the same "size" that is only rated for 50v. About things like traces on the circuit board, traces will need to be further apart to not have issues with higher voltage, so the circuit board might get larger, making the cover/box larger. So designers must decide, what do I want to build and what limitations do I want to be stuck with.....or how much cost will the market for this specific product tolerate? So too much Voltage will/can blow it up even when it is turned off.

Amps are current and amps make heat when they flow in a conductor. More amps you need larger traces on the circuit board. So for example I want to design a board that will handle 30amps. I design for 35a just to be safe. I have a micro computer on the control board. I also have designed in a little circuit that can measure the current that is flowing. Also part of the design is a way to cause more or less current to flow. The software manages to do a conversion from the PV input to the battery/charging output. The amps that flow are regulated to stay within the bounds of the design. The panels don't force amps into the charger. The charger is a variable load and demand amps from the panels. So the charger is in control of the amps that actually flow and those are limited by the panels possible output under current solar conditions AND the internal limits of the charger. So the MPPT charger will not create a load in excess of its design limits under normal operating conditions. I would expect there might be some failure mode where the charger becomes internally damaged and then basically shorts the output from the panels. That would be a condition that you might want to fuse for, if over-paneled. That would protect the wiring from maybe getting too hot.
 
Most inverter controllers will specify a limit on total PV input they can manage. Stay well within the Voc and the total kW array limit and you'll be fine.

If the array can produce more current than the rating for the controller, the controller will simply clip current at/near the limit.

Here's an example - it's from a larger Fronius grid tied inverter but the principle is the same:

View attachment 63765

There are two MPPT inputs, one with a higher current limit of ~25A, the other with a limit around 15A. Both have the same sized array connected, one with a different string orientation mix than the other.

Can see the current clipping one MPPT input for ~6 hours from about 9am to 3pm. This is normal during good solar production periods and is making efficient use of the inverter. Yep a bit of array production potential is lost but that's well and truly made up for when conditions are no so good.

Often such over panelling is done via split orientation (easterly and westerly facing) arrays in parallel which tends to keep total current down somewhat by spreading output over a longer period of the day.
This explanation makes a lots of sense to me and paints the correct picture in my mind. The same concept for a compressor, or any other load, in a refrigeration system. Give it the correct voltage and it will take the current it needs/wants and no more. Double it's voltage and *POOF*, out comes the magic blue smoke.
Anyway, I've been thinking of designing a system with the new high watt panels to run a small heat pump system for an insulated storage building for long term food storage but was concerned about over sizing the panels if I design for low light conditions. Now that's not such a worry as long as I keep the voltages where I need them.
 
so, you would say that on most mppt chargers i can over voltage, but should never over amp
Never never never allow PV combined voltage to exceed the controllers rating.

over amping isn’t possible, since the controller DRAWS amps, panels do not PUSH amps. However, a large array can push a low cost controller to draw maximum amps for so long, that it can overheat if not managed properly…
 
This has been correctly stated already but it is sometimes misunderstood. So I will toss out some more words.

The max PV in is limited by the internal design's parts. If you want to design for max PV volts of 50v or max PV volts for 200v, many things will be different and more expensive for the 200v solution. For example a capacitor that can take 200v without an internal short will be larger and more expensive than the same "size" that is only rated for 50v. About things like traces on the circuit board, traces will need to be further apart to not have issues with higher voltage, so the circuit board might get larger, making the cover/box larger. So designers must decide, what do I want to build and what limitations do I want to be stuck with.....or how much cost will the market for this specific product tolerate? So too much Voltage will/can blow it up even when it is turned off.

Amps are current and amps make heat when they flow in a conductor. More amps you need larger traces on the circuit board. So for example I want to design a board that will handle 30amps. I design for 35a just to be safe. I have a micro computer on the control board. I also have designed in a little circuit that can measure the current that is flowing. Also part of the design is a way to cause more or less current to flow. The software manages to do a conversion from the PV input to the battery/charging output. The amps that flow are regulated to stay within the bounds of the design. The panels don't force amps into the charger. The charger is a variable load and demand amps from the panels. So the charger is in control of the amps that actually flow and those are limited by the panels possible output under current solar conditions AND the internal limits of the charger. So the MPPT charger will not create a load in excess of its design limits under normal operating conditions. I would expect there might be some failure mode where the charger becomes internally damaged and then basically shorts the output from the panels. That would be a condition that you might want to fuse for, if over-paneled. That would protect the wiring from maybe getting too hot.
Thank you
 
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