Poor solar input with AC200P and third party foldable solar panels

Hi guys

I’ve purchased an AC200P and a pair of third party foldable 200Wp solar panels. Thus 400Wp total.
After putting them to the first real world test during a camping trip I’ve noticed that the solar input is much much below anticipation.

With the the panels connected in series, the Bluetti only draws about 150-180W.
Even with clear skies, no shade whatsoever, and the sun up high.
Strangely enough, the input voltage readout on the Bluetti is about 31V, while the minimum input should be about 35V.

Results of my test set-up, on a lovely sunny day:

Bluetti solar-input readout: 31.1V / 5.1A / 158W
Charging mode is set to PV

When I disconnect and measure the V(oc) of both panels in series, I get about 38.8V
For the panels individually I measured:
panel 1: V(oc) = 20.1V and I(sc) = 9.98A
panel 2: V(oc) = 19.8V and I(sc) = 7.39A ; noticably less but not dramatic
for reference, the listed values of the panels: V(oc) = 23V and I(sc) = 11.7A

In theory, using the value of the least performant panel in the system,
I should be getting about 7.39A x 38.8V = 286.73W - Right?

My measurements don’t seem to comply with the readout on the Bluetti.
Too bad that I don’t have any other solar panels available to cross-check with.

Am I doing something wrong?
Is there something wrong with my unit or my panels, or both?

Thank you very much for your time and replies

No, you need to be using the voltage under load not the VOC. Your voltage is too low at 31.1 volts as the minimum charging voltage for the AC200P is 35v.

As a panel received a load the voltage drops. You do not list your panels voltage under load spec but it should be listed and will be less than the 23V you show for the VOC. If you add a third panel of the exact same type, your voltage will increase to a more compatible voltage range and your results should improve. The higher the voltage, the better the results. Assuming your panels are performing to specs that is.

Thanks for the reply

That does make sense, however I don’t fully understand why the Bluetti is still charging then, at 31V, while the minimum should be 35V.
I bought the AC200P and 2 panels as a set. Looks like I’ll have to have a word with the vendor if the 2 panels prove to be insufficient to charge the system at a respectable rate…

These are the full specifications of the panels:

The 35 volts is not an absolute and there is a little wiggle room on the minimum. In looking at your specs provides, you should be seeing 36 volts under load with two panels connected in series. I think the issue is that you are not getting the 18 volt Vmp (voltage maximum power (load)) that they are rated for and since you are at the extreme bottom of the scale for minimum volts you are not seeing acceptable results.

Panel out put will rarely exceed 80% of the rated wattage in great sun conditions when properly aligned. If your two panels were exposed to perfectly clear mid day sun, properly angled and aligned I would expect around 300 to 320 watts under those conditions. My best guess is that the low panel voltage is the issue, you do not have perfect sun and panel angle or the panels simply are underperforming.

If it were me, I would talk them into selling you a third panel at a discount and connect all three in series, this would eliminate the low voltage issue because then you should be seeing around 45 volts or so which would then be above the minimums. With three 200 watt panels connected in series producing 45 volts I would expect them to out put around 450 to 480 watts in PERFECT sun conditions assuming the panels were correctly aligned and rotated during mid day sun. If that is not then the case, I would think the panels were not outputting as advertised. This is sometimes the case for lower cost panels. In any case, even the best panels will not output well if not angled, rotated and no shade present correctly.

If you did purchase the third, I would ask for an agreement that you could return all three if they did not at that point perform as they should.

1 Like


The vendor asked me to send the lesser performing panel back under warranty, and I have received a replacement panel from them just now.

I am now reading an average input on the bluetti of around 31-33V and 250W (out of 400Wp) in bright afternoon sunlight.
Considering the speculations above, I think that’s about the maximum I will be able to generate with just these 2 panels, as the setup is still cutting corners with the 35V lower limit.

So, huge improvement, but they really shouldn’t have sold the bluetti as a set with just 2 panels in my honest opinion. For now I’ll see if I can manage over a longer period of time, and if not, I should look into getting the 3rd panel.

The main issue appears that the vendor that sold you the panels did not sell you a set of panels that had sufficiently high voltage to operate efficiently. You can find individual panels with higher voltages that will perform better. If I were in your shoes, I would bite the bullet and get another panel or two to raise the voltage level higher.