My AC500 currently has 6 panels connected. Two strings of three panels each connected to PV1 and PV2 respectively.
The panels have 460Wp, a Voc of 41.8V and an Isc of 13.78A.
That means that one string of three panels has a Voc of 125.4V, so well below the limit of 150V.
Now that I’ve learned about how the “PV parallel” mode works, I want to add 3 more panels. I just want to make sure that we don’t damage our AC500 with that.
I want to connect three of these strings with three panels in parallel. The Voc would still be 125.4V. But the Isc would rise to 41.34A.
I’ve read online that some solar chargers can only take 125% of the maximum current while others can take 150%.
The AC500 with “PV parallel” on can absorb 30A.
So is it okay if I hit it with 41.34A?
Because that would be almost 138%. And I don’t know if this is already pushing the limits here.
My second question is how to connect the three strings in parallel. I don’t want to push 30A over those thin cables of PV1.
Can I leave one string on PV2 and connect the other two strings in parallel and connect that to PV1 and the “PV parallel” mode will switch something internally so all three strings are connected in parallel?
Sorry for you, but your plans are not going to work out well. Quite simply because each of the ac500 solar inputs (dc1 or dc2 of your ac500) is limited to 1500W and 15A. You have already almost saturated the max power for dc1 or dc2 with a string of 3 panels (3x460w = 1380 W). putting a new string in parallel will only add 120W at best, without forgetting that you will be for the 2 lines in parallel on dc1 for example at more than 27A… for 15 A max for each DC… you will be limited and you’re not going to recover any extra power.
In your case, the only thing left for you to do is to use the solar inputs of the B300S, you can add panel, UP to 500w per solar input of each of your b300s (VOC 12V - 60 V, 10 A, 500w max). If you buy the bluetti d050s (charge amplifier) you can add 500W more by connecting panels to the d050s which will plug into the b300s ac-dc adapter input. That will give you a lot of extra solar cable to pull !
What happens every time a cloud is between the panels and the sun? What happens in winter? What happens during sunrise? What happens during sunset?
Am I only going to see 120W more during all of those times?
Of course not.
During a summer day with overcast 3 panels don’t hit 1000W. So 3 parallel strings of 3 panels won’t hit 3000W.
But if 3 panels are producing 1000W then 9 are going to produce 3000W. So 1000W more than my current setup.
I can’t really utilize more than 3000W anyway. But the added power in the morning, the evening and every time there are clouds would help a lot. And that is going to be a lot more than 120W.
On top of that I would have to buy more DC breakers, more overvoltage protection (against lightning) and quite a few more meters of cable.
And all that just for the battery packs to be full faster and the PV input producing zero watts for more hours each day than is already happening right now.
I can still do that in the future if I actually need more energy during sunny days. But right now connecting three more panels is all I need or want.
So I don’t want someone to school me about how I should change my plans. I simply want to know the answers to my two questions.
Sorry if my words irritated you, that’s not my intention. I’m just trying to help people.
For your first question “So is it okay if I hit it with 41.34A?” the answer is that there’s no problem, you won’t damage your AC500. The important thing is to respect the maximum voltage (150 V), as the current will be automatically limited by the AC500.
The AC500 will not limit your 41.34 A to 30A… it will limit to 15A max on DC1 input… and to 15A max on DC2 input.
In your case, if you put both strings on DC1, at most you’ll have 13.78A X 2, so the DC1 input will limit to 15A.
On your question 2: “Can I leave one string on PV2 and connect the other two strings in parallel and connect that to PV1 and the ‘PV parallel’ mode will switch something internally so all three strings are connected in parallel?”. No problem either, you can put one string on DC2 and 2 strings on DC1, you don’t have to do anything, the AC500 takes care of itself.
PS I offer you this alternative solution, but it’s up to you!
I understand that sometimes your panels don’t produce enough, and so you want to oversize your panels by putting a second string in parallel. So on gray days you will have more power. However, on days when the weather is very nice, the DC1 input where you connect the 2 strings in parallel will limit the power to 1500W and 15A, you could lose a lot. An alternative solution, which I have proposed to you, allows you not to lose anything both on the day when it is gray and on the day when it is sunny: it is to use the solar inputs of your B300S units or even the AC-DC input of your B300S with the BLUETTI D050S: You will be able to add panels and not be restricted by the 1500W and 15A limit of the DC1 or DC2 inputs of the AC500.
Even if you add an additional string in parallel on the DC1 port, you still have the possibility that I described above to add more panels.
And how do you know that? Do you work for bluetti? Many manufacturers state the maximum allowed over paneling their solar chargers can take. (I’ve seen up to 150%. But also just 110%.) And there is definitely a limit for bluetti devices too. I don’t even want to know the specific limit. Just if I’m below. And I want to know from someone who actually knows the device. Because:
The AC500 will not limit your 41.34 A to 30A… it will limit to 15A max on DC1 input… and to 15A max on DC2 input.
This makes me question where your knowledge comes from. I have not just once but three times used the term “PV parallel”. You obviously don’t know what that means and thus keep insisting that the limit isn’t 30A.
Makes me doubt that you’ve worked with the AC500 or at least looked at its manual. Or any of the other devices from bluetti that support this mode.
So it would be great if someone who actually owns one of the devices that support “PV parallel” mode and has over-panelled it, could answer my questions.
I would also be happy to see an answer from @BLUETTI_CARE about this.
@Robert1
Hmm, sometimes users just want to help and answer a question, that’s exactly what a forum lives on, that users also comment on a question.
If this is not desired, or ‘only’ a supporter should answer, then simply send the question by e-mail to BLUETTI support. Then you will really only get an answer from there.
My opinion on this … I don’t think I need to write any more on this topic.
(And no, I don’t have an AC500 but an EP600, so there will be no further comment from me on the AC500)
Dear @Robert1 please remember that you are asking your question on a public forum, where everybody is using their time for free and nobody is required to provide the source of information got from personal experience.
And as such, you should not pretend and get arrogant with people that are kindly trying to help you, especially when they are providing information that are correct.
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As for one general rule in electronic, that you clearly don’t know: voltage is provided by the source and current is requested by the destination based on its resistance.
Hence, your only concern when designing your photovoltaic panel configuration is to never exceed the maximum voltage that your solar charger is able to accept on its input. End of story, end of concerns.
The solar charger maximum current, which for the AC500 is 15A for channel1 and 15A for channel2 is the maximum current that the charger can request while changing its internal resistance while tracking to get the maximum possible power out of the solar array. Connecting a solar array with a potential Isc of 10000 A to a PV channel of an AC500 is perfectly fine and that still means the AC500 will get a maximum current of 15 A while tracking and changing its resistance.
Tracking, which for AC500 is done with an MPPT algorythm, is done independentely by the 2 solar chargers on the 2 inputs by changing the resistance for the sole scope of getting more power. Increasing the resistance results in increasing the amperage but lowering the voltage, decreasing the resistance results in lowering the amperage but increasing the voltage. Since volt*ampere=watt, and the solar irradiation is changing continuously during the day, the algorythm is tracking and changing its resistance to get the best wattage out of the photovoltaic arrays at any moment. And the resistance changing is done by the internal logic by never exceeding 15 A per channel by design.
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Since AC500 has 2 charge controllers and those tracks the voltage and current independently, the PV parallel mode which in fact as the name suggest parallelize the 2 controllers, should be enabled only if you have a single string and you would like to get the advantage of doubling the current capacity, altough this will have the disadvantage of using only 1 algorythm.
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On your case, since you already have 2 strings, it’s probably a better option for you to keep the 2 controllers separated, each with 1 string, so they can track more efficiently the different voltage and current of the 2 strings since they will have different irradiation during the day. On this case, as an example, shadowing on 1 string will not affect the performance of the other string which will continue to produce.
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At this point, I wish it will be already clear that if you would like to add a 3rd string you can just parallel it to another string to increase the current into one of the 2 charge controllers and therefore to increase the production during low irradiation times such as in the morning or evening or during a cloudy day.
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As a last note, you should make sure the 2 strings you are parallelizing have the same VoC. If your typical 3-panel string has a VoC of 125.4 volt, the 3 panel string you will parallelize to this string should have the same VoC to avoid the panel back-feed diodes to dissipate the bias, but this is another story for another thread.
especially when they are providing information that are correct .
None of them talk about PV parallel mode. And you too keep talking about 15A per channel when you also state that the two chargers can be run in parallel doubling the current capacity. So the limit is in fact 30A and not 15A.
On your case, since you already have 2 strings, it’s probably a better option for you to keep the 2 controllers separated, each with 1 string, so they can track more efficiently the different voltage and current of the 2 strings since they will have different irradiation during the day. On this case, as an example, shadowing on 1 string will not affect the performance of the other string which will continue to produce.
I don’t see the advantage of that. All 9 panels are next to each other and look into the same direction. And there are no shadows.
At this point, I wish it will be already clear that if you would like to add a 3rd string you can just parallel it to another string to increase the current into one of the 2 charge controllers and therefore to increase the production during low irradiation times such as in the morning or evening or during a cloudy day.
That would mean cutting off some of the production while still below 3000W. If I did it like that and 3 panels were producing 1000W then 6 panels on one charger wouldn’t produce 2000W but 1500W. With PV parallel mode enabled I would be getting 500W more out of it.
As a last note, you should make sure the 2 strings you are parallelizing have the same VoC. If your typical 3-panel string has a VoC of 125.4 volt, the 3 panel string you will parallelize to this string should have the same VoC to avoid the panel back-feed diodes to dissipate the bias, but this is another story for another thread.
I’ve got 9 panels of same make and model. So that won’t be an issue.
But it’s still 3 strings with 3 panels each.
And none of that answers my second question:
Does the “PV parallel” mode of the AC500 connect DC1 and DC2 internally? Or do I have to connect them externally with a y-cable?
Or asked another way: I’ve got a single panel with Voc 120V and Isc 20A. Can I just connect that to the MC4 connectors of DC1 and DC2 will get half of the current? Or do I need to split up the MC4 connectors of the single panel with a y-cable so that I can connect it to both externally?
@Robert1
You can charge it with 41A and the machine will limit the current.
There is no need to open PV parallel, PV parallel mode working conditions do not quite match your description. But if you want to turn on PV Parallel, you will need a Y-type charging cable, which is more complicated to operate. (PV Parallel Enable only needs to be turned on in one case: when the same solar array with power greater than 1200W and open circuit voltage less than 150V is connected in two ways)
You can directly choose AC500 to connect “3 panels in series and 2 panels in parallel” solar panels in each circuit, which is more convenient.
So I will need a y-cable to even try this. Still cheaper than all the additional cabling, circuit breakers and lightning fuses.
You can directly choose AC500 to connect “3 panels in series and 2 panels in parallel” solar panels in each circuit, which is more convenient.
Maybe this is a translation problem but I don’t understand what that means. Did you want to write “3 panels in series and 2 strings in parallel”? Because that would make more sense.
But it would also mean that I would be over paneling a lot. And I would need 12 panels for that. I only have 10 and I don’t think that I can get that same panel again.
If you ask politely, have some patience and build an healthy conversation, don’t worry you will understand. Everybody is here to help.
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PV parallel enable the controllers to track voltage and current together for them to be used together with the single same input. That will not parallel the channels for you.
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15 A is per channel, there are 2 channels, the parallel mode will double the current to a total of 30 A for a single array input connected in parallel to both channels. Not on 30 A per channel.
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The single array input should then be connected to both the PV inputs as already stated.
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This whole behaviour is necessary because 2 solar charge controllers using 2 algorithms cannot be used with a single array with paralleled input because that will result in the algorithms of the 2 controller fighting for each other trying to conflictually changing the resistance.
All that has been the starting point for me. I never said anywhere that I thought the AC500 could consume 30A per channel. The point was always that with “PV parallel” mode on it can do 30A in total.
And did you see how short that answer from bluetti was while answering both of my questions? Refreshing after all those walls of text.
don’t worry you will understand.
Then please tell me what “3 panels in series and 2 panels in parallel” means.
In parallel mode, the 2 mppt are put in parallel inside your ac500, this means that the AC500 will connect pv+ of dc1 with pv+ of dc2 and pv- of dc1 with pv- of dc2… In fact it comes back to do what you do outside the AC500 according to your diagram.
So what I explain previously for 2 mppt located on 2 separate solar generators is transposable for 2 mppt which are located inside your ac500. In summary: when your panels are going to produce more than 1500w (exceeding the max power for example on dc1/mppt1) then it is interesting to put dc1 and dc2 in parallel either via parallel mode or as you do with your wiring (this amounts to same): for example, to simplify, your panels can produce 2000w at a moment then the mppt1 can take the max, 1500w and the mppt2 take the rest, that is to say 500w, in a stable manner. In this situation it works well in general, and you achieve the objective of getting the maximum power from your panels… However, there are situations where it can work bad: there are clouds and the sky is gray (or you are early morning or late afternoon) assume your panels only produce 1000w max at best at this moment : as your panels array is connected to mppt1 and mppt2 in parallel… Both will try to get the most out of your panels… So for example at the start mppt1 will take 1000w from your panels and mppt2 will take 0w… But mppt2 some seconds or even tens seconds later, following its algorithm, it adapts to draw more power, mppt2 starts by taking for example 200W and in doing so it destabilizes the optimum power point found by mppt1, and then the power drops for mppt1… It is possible that mppt2 ultimately manages to draw the 1000w max from your panels before mppt1 in turn begins to destabilize the optimal point of mppt2. Most likely in this situation where the optimal point of power extraction from your panels in the example 1000w, is never regularly held… And your ac500 will draw less than 1000w because of the competition between the 2 mppt. In this situation, you should not activate parallel mode (or connect pv+ of dc1 to pv+ of dc2 and pv- of dc1 to pv- of dc2… which is the same as parallel mode). I’m afraid that no one here (I’m an engineer) or even bluetti will be able to tell you if in the end it’s better to activate parallel mode on a single panels array… Or not activate parallel mode and keep two separate panels array, one on dc1 and another on dc2.
It depends on the weather, the power you can get from your panels. If this power very regularly exceeds 1500w, your configuration (parallel mode) may be relevant. But on the other hand, if your panels produce less than 1500w very regularly, it may work less well. That’s just my opinion. Only you can test the 2 configurations (a single array with the mppts in parallel or 2 independant arrays and 2 mppts non-parallel/ independant) For a long period to know which one allows you to draw the most energy from your panels taking into account your situation (sun, weather, etc.)
