I have Renogy 320W panels, specs below, and I am trying to put four in series but keep getting an overvoltage warning.I currently have three wired in series with no problem, and according to math from the AC300 adding a fourth shouldnt be an issue. Voltage for the three in series is between 98V-103V, which tells me that adding a fourth shouldnt be an issue. I am hoping that I was just using the wrong number to do my calculations, otherwise I will be needing to get Bluetti Support involved. Please let me know what you guys think.

Max Power 320W
Open-Circuit Voltage (Voc): 40.1V
Optimum Operating Voltage (Vmp): 33.7V <---- Using these
Optimum Operating Current (Imp): 9.5A <---- Using these
Short-Circuit Current (Isc): 10.08A

This website also shows that it shouldnt be a problem as the max voltage is 150V and max amperage is 15A.

That is what I thought as well but the site was using the operating voltage. So I decided to mess around with my panels, I have a total of 10, and it turns out that one of them runs a bit hot on voltage. Solution was to pair it with another for the AC200P and then use the “normal” panels in a series of four for each of the two array on the AC300. Works like a charm now. Getting much better charge and utilizing all of my panels much more efficiently now. I am going to leave this here to help anyone else with this issue.

I think you are doing your math incorrectly. Four of these panels in series would exceed 160 volts which is above the 150 volt limit. You are taking the 33.7V operating voltage for your calculations which is not correct. You need to use the 40.1 VOC figure for the max voltage of each panel.

There is a solution for overvoltage but it wastes power. Adding a resistor (5 ohm or more) in series will drop sufficient voltage but only if you need to supply over the Vin limit on purpose. Using less panels in series is better.

I respectfully disagree with the idea that a resistor in series will be helpful in this situation. If the goal is to not exceed the Open-Circuit Voltage (Voc) spec, then a resistor in the circuit will have no effect. A resistor produces a voltage drop only when current is flowing—but Open-Circuit Voltage (Voc) is, by definition, the voltage produced with the current is zero.

You also need to take into consideration the cold weather that may exist in your area. Simply adding up the VOC in a cold area might work for the majority of the time, but as the weather gets cold your voltage will increase.