Monster power bank. I use it for running all my bedroom electronics and topping of phones and tablets overnight. Every 2 or 3 days, I recharge the unit from a larger off-grid inverter connected to solar panels. There is a fan that comes on briefly at power on, but my usage must be below the level that would keep it on. If it stayed on, I would not be able to use it in the bedroom. Lucky, so far.
The sale price is competitive, and actually might be a bit of an edge, given the extreme portability, light weight, 2 x 300W AC, and almost 1/2 KWH, which is unusual capacity at the sale price.
I find a mild manufacturing "electronics" odor still slowly wearing off as the unit heats up and cools down. This sometimes happens with electronics that have high-power transformers inside. But I will monitor it closely, and contact support of the odor does not completely wear off within a couple of weeks.