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.
.
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.
.
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.
.
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.
.
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.
.
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.
Thank you for the reply.
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.
.
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.
.
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.
.
The single array input should then be connected to both the PV inputs as already stated.
.
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.
@Robert1 The connection diagram for “3 in parallels and 2 in series” is shown in the following draft.
That’s not applicable here. I’m not trying to connect to the MPPTs of two different power stations.
Even bluetti themselves say it works like I want to use it: PV Parallel Enable - #2 by BLUETTI
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.)
(I’m an engineer)
Do they pay you well for writing long texts about untested assumptions?
Again: What experience do you actually have with bluetti products?
Robert1,
you don’t believe in anyone, very good. so believe in yourself and what you see. plug your panel string into your ac500, watch the power arriving on your ac500 early in the morning or late afternoon, on a cloudy day, at midday in full sun. and draw your conclusions yourself.
goodbye Robert1!
I think Robert1 is a Troll 
That’s not true. bluetti and ndwr wrote helpful answers.
You did not. And you made it clear that you don’t know the AC500.
@Marcus
I asked questions. I got actual answers from people who know stuff.
And I got replies from people who wrote a lot of text while not answering any of the questions.
Such people need to be called out. And that doesn’t make me a troll.
Hello Robert,
I’m active in a few forums, but I’ve never heard anyone ask for help in your tone. You get free answers without having any right to their content. You should say thank you and silently assess whether the answer is of any use to you or not. Of course you can have a different opinion. You are entitled to a competent, correct answer if you contact Bluetti support, or better yet, the dealer from whom you bought the devices.
Marcus
You did see that they answered, didn’t you?
This is their forum.
And the dealer is bluetti themselves.
You called me a troll. So thank you for that helpful comment. 
It is understandable to seek guidance and advice from others, but it is more important to realize that BLUETTI Forum is a place for collaboration and mutual respect. It is not a place for twisting the professional advice of our members to fit one’s agenda.
I hope our members approach the forum with an open mind and a willingness to learn from others as our community is comprised of individuals with valuable insights and experiences to share. By engaging in thoughtful discussions and asking questions with genuine curiosity, we can all benefit from the collective knowledge and expertise that our forum has to offer. As our forum guidelines say: Be respectful. Cheers! 
