I have five 1500W arrays, each with a cumulative Voc slightly above 150V (cca. 160V) and so far have been using the D300S voltage reducers to connect them to my three AC300 units. The D300S reducers have been working great (produced over 5MWh in the past 9 months or so), apart from the whining noise they generate above 700W and the relay click-clacks around sunrise/sunset.
Bluetti Support put out an AC300 solar charging video on YouTube a few weeks ago where they explain (for the first time, I believe) in some detail how the PV Parallel setting is supposed to work.
They claim (around 3:10 in the video) that serial arrays with Voc between 150V and 500V can be connected this way. They also mention (at around 3:29) that an “optional” parallel cable is required, which makes sense, however they don’t mention if this is a standard pair of parallel cables or something special, nor is it something that can be found among the accessories they are selling.
So took a deep breath and gave it a try with a standard set of parallel cables I happen to have.
Set both DC channels to “PV” and enabled PV Parallel. Then turned on the solar isolator of the 1500W/160Voc array.
As soon as I did that, the AC300 immediately generated an over-voltage protection alarm for both PV channels, which is precisely what I expected.
So my questions:
[1] If the MPPTs can only handle max. 150V individually, how are they supposed to be able to handle 500V (max) in parallel mode?
[2] Is the parallel cable shown in the Bluetti Support video a standard one or a special one with some built-in voltage reduction and/or extra circuitry? If the latter, where can one obtain this cable?
Thanks in advance for any input.
Hey @gbk
Maybe link that video?
150V is the limit, no matter if you connect series or parallel. Im pretty sure, the 500V was mentioned in another context.
Thats dangerous! Just exceed the max voc by a few volts can kill the MPPT. You exceed it by 10V. This could be a big problem in some cases.
greetings
Erik
It’s on the Bluetti Support YouTube channel, as mentioned. Should be trivial to look it up but here you go (with the timestamp where it clearly states “150 < Voc < 500V”):
https://youtu.be/PxwjWy86Yco?t=190
And as I said, I’m using those rooftop arrays with the D300S step-down module (three of them), which brings the voltage down to around 115V for the AC300 DC inputs. Works as intended.
My questions were:
[1] If the MPPTs can only handle max. 150V individually, how are they supposed to be able to handle 500V (max) in parallel mode (as implied in the YT video)?
[2] Is the parallel cable shown in the Bluetti Support video a standard one or a special one with some built-in voltage reduction and/or extra circuitry? If the latter, where can one obtain this cable?
Slightly earlier in the video, they say that the total voltage is not to exceed 150V.
Indeed. Which I believe also is a bit ambiguous, since 2400W refers to the two MPPTs combined, while the max Voc is 150V each, individually, if my understanding is correct.
That FAQ is in a section of the video though which talks about attaching two individual (preferably serial, as the video states) arrays to each MPPT and in that context it makes sense.
That section where it shows that slide with “150< Voc < 500V” is the rooftop solar / PV Parallel setting chapter where the input from a single serial array with Voc over 150V is split between the two MPPTs. As mentioned above, tested it with a standard set of parallel MC4 cables and an array with 160V Voc and it does not seem to work (gives overvoltage error on both PV/DC channels, as one would expect).
@BLUETTI_CARE
Could you please clarify?
Thank you.
-
Usage Scenario of PV Parallel Mode:
When there is a whole solar panel (installed on the roof and cannot be removed), the voltage of this solar panel is within 150V but the current is very high. Since our machine limits the current to 12A through one MPPT, any excess will be wasted. In this situation, you can enable PV parallel mode, which allows you to split the large current in half. For example, if the working current of the solar panel is 30A and the voltage is less than 150V, connecting to one MPPT would only input 12A; but after enabling PV parallel mode and splitting the solar panel into two paths, the current is halved, giving each path 15A. This way, you can maximize the solar panel’s energy utilization. -
Reasons for Errors When Enabling PV Parallel Mode:
It splits one solar panel into two paths for charging, so the voltage of the same solar panel is the same. If it detects that the DC1 and DC2 voltages are inconsistent, it will trigger an error. -
Maximum Input Voltage for PV Parallel Mode:
The maximum input voltage remains 150V. -
Using PV Parallel Mode:
To use PV parallel mode, you need a Y-split MC4 cable, which is the parallel cable in the video.
(However, PV parallel mode may not be suitable for your usage situation.)
@BLUETTI
Thanks very much for the confirmation. It seems then that the 150Voc is indeed a hard ceiling, even for the PV Parallel setup, as suspected. Will continue using the D300S voltage step-down units then. They’ve been working perfectly for close to a year
The only thing I still fail to understand is the “150V < Voc < 500V” reference in the video (at around 3:10, as mentioned above) while discussing the PV Parallel settings. Where does the 500V Voc come from?
Thanks once again.
This is likely an error in the subtitles from the video team. Thank you for the reminder; I will inform them to make the corrections.
I just found why the slide shows a 150V < VOC < 500V. It is for a situation when the AC300 is used with the D300S PV step down module, which is for rooftop solar applications.
That slide should not be showing the “150V < VOC < 500V” statement as the voiceover and subsequent slides all refer to the panels being within the AC300 input spec without the use of the D300S.