Bluetti AC180 Solar panels charging at 70%

I have a Bluetti AC180 with 1 100w solar panel. I check the solar panel at it is 100w. The end of the Bluetti cable is at 100w. It will only charge at 70w. When I put 2 panels in serial or parallel I get 200w using volt meter at end of the Bluetti cable plugging into the unit. I get 140w. Is the 30% decrease normal?

@vincelh It is normal. The intensity of the sunlight, the angle you place the solar panel, and the conversion of the solar panel itself, all those factors will affect the final efficiency of the solar panel. I suggest that you can connect two solar panels in series and do more tests under different situations.

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I did try connecting is series and parallel. The same results. See above.
YouTube videos I have seen shows this figure to be higher. Example. Youtuber used a charger instead of solar panels. 22v at 7.7 amps = 169 watts. The AC180 screen states 162 watts. Less than 10% loss.

Curious how you are measuring 100 or 200 watts without that amount of power actually transmitted. In any case you will almost never see the full amount of wattage spec from any panel. 75% is fairly good in great sunlight.

1 100 watt panel. Use voltmeter at the end of the 2 cables coming out of the solar panel. 19.5 volts and 4.95 amps = 96.5 watts. Connect the solar cable supplied by Bluetti to the solar panel cables. I get 19.5 volts and 4.95 amps = 96.5 watts at the end of the Bluetti cable barrel connector. When I connect the Bluetti cable to the AC180 the screen and app shows between 65 and 70 watts.

How are you measuring the amps without the current flowing? If the barrel connector is not inserted into the Bluetti, there is no load for current to flow.

I am using a voltmeter with no load.

You are measuring what is known as open circuit voltage (Voc) and short circuit current (Isc). Multiplying them together does not tell you what the solar panels peak power is. What you need to further do is multiply the result by what is known as the “fill factor” (FF). For a well functioning solar panel, FF can vary widely. In your case it looks like it’s about 0.65 to 0.70. It’s completely normal.

you are not measuring amperage then, just the voltage.

As @Scott-Benson already mentioned. When you just check plus and minus with a voltmeter the value you see is the Voltage. You only can measure amps by connecting it to a load. Otherwise there is no current flowing