A few years ago, I plugged a single 100W solar panel into a battery pack that advertised it accepts 18 volts. I left it plugged in, on my deck, for hours. When I came back, there was a foul smell and some parts of the battery pack had turned black, apparently from getting charred. The battery pack no longer worked at all. I was very fortunate that only the control circuit had been destroyed and the battery cells (and my deck) had not been touched.

Lesson learned: don't skimp on Li-ion battery packs!

Also, I have a question about this article. Don't EcoFlow battery packs have a circuit that checks the incoming voltage and automatically shuts off charging if the voltage is too high? I would also expect a loud alert.