AC200P PV charging problem

Dear Bluetti Community,
We are having a problem with charging our AC200P unit via PV and would like to ask for your help.
The unit is charging properly via AC wall outlet (we get 375W) and with car lighter port input (we get around 130W). Unfortunately, we can not get the unit to charge via PV, despite the fact that we performed all the tests during a no cloud super sunny day and between 11 to 3pm (we live in Los Angeles, where the sun is not the limiting factor!).
We have 2x100W Renogy rigid solar panel, each having VOC of around 22-24V. We confirmed it in both by using a multimeter. When we connected them in series, we got around 44-45V and we confirmed that the same V was kept after connecting all the required cables (MC4 to XT90 and XT90 to aviation plug). This should be enough, as the AC200P working range is 35-150V. We selected PV in the DC input source setting and connected the aviation plug (red dot with red dot).
On the screen of the AC200P the input voltage fluctuated between 40-45V and at the beginning we got around 150W of input power, which would be pretty good! However, after a few minutes, even though the input voltage stayed constant, the input current and power dramatically started to lower down and finally got to a constant fluctuation between 0-10W. Thus, despite the initial charging, the final low power was of course not enough to keep recharging the unit, which started to de-charge. We tested on 3 different sunny days, both with the panels flat and sun-oriented, and got the same rapid input power decrease.
Have any of you experienced a similar problem or have any thoughts on how we could troubleshooting? Thank you in advance!

One thought I had is that perhaps when the panels are under a heavy load, the voltage drops (normal for panels) just enough below the minimum threshold for proper charging. Three panels in series would confirm this. I have two renogy rigid (solar suitcase) panels and they run 16 to 18.5 volts when under load.

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@Simona Can your solar panel charge other devices properly? like. If it is not a problem with the solar panel, it is possible that the AC200P needs repair.

I had this same issue on my ac200p. I just had it replaced under warranty after three months of battle and I am having the same issue with the new unit. One would think that it is my panels, but I cannot figure out what the issue could possibly be with my panels. They are delivering, in full sun, 40-48v and 5-8amps. I have two renogy 200watt panels wired in series, which are putting out their spec power. The display on the bluetti itself does not correlate with my multimeter and reads consistently lower/completely wrong when compared with my multimeter.

Im at my wits end with this issue and it seem like it has to be my panels, but facts are facts and I cannot imagine how this could be my panels when they are delivering more than the required 35voc and plenty of amps.

Edited to say: I had two years of trouble free use until recently. Again, this would maybe indicate my panels but they are delivering more than adequate power and the ac200p should be receiving nearly 400 watts in full sun

Are you measuring under Load?

what do you mean by under load? also, what could have changed when I began with this setup to now? it has been unchanged since the day I installed this on my van

Under load would be when you are receiving a substantial amount of solar input. The more output from the solar panels, the more load they are under. When the solar panel output load increases, the output voltage decreases. You will see maximum voltage when measuring the unconnected output leads from the panel and the least voltage in the brightest sunlight producing the highest wattage.

In full sun I get the spec output, 48v and 8 amps.

I think you have something wrong with your measurement method. Full sun and 8 amps should be producing the lowest voltage. You say you have (2) 100 watt renogy panels but 48 volts and 8 amps is 384 watts which the panels are not capable of producing. I suspect you have an issue with your multimeter or need some clarification on how to measure amperage.

I have two 200 watt renogy panels. These: 200W 12V Monocrystalline Solar Panel | Renogy

I’ve used multiple meters to check, and in current full sun (I live in Seattle so there is that) I am getting between 39 and 45 v and 2-8 amps depending on conditions. I’ve taken multiple videos for troubleshooting. I’m also using the testing method described here:

I am probably doing something wrong, but I am not sure what else there could be going on here.

Edited to add: would getting an mppt controller allow me to get more accurate measurements of the panel under load? Could I then connect to the ac200p after the controller? I know the ac200p has one as well but what I’m reading indicates an mppt controller can give accurate measurements of the panel under load.

This is NOT what you would do!
You measured the Short Circuit Currentand the Open Circuit Voltage.

This is useless and shorting out your Panel is potentially danging to it.

You messured the VOC pont and the ISC point
But Power is 0 at this points.

You need to Measure Voltage and current. at the same time.

Waht is the Voltage And current under load