Plausibility of ancient extraterrestrials

[Fake Messiah]

It actually is a weird one, because we don't just have descriptions of these artifacts, we've found quite a few of them intact.

If we are talking about the Baghdad battery then from what I know there has only one been found and it was stolen from the museum in 2003.

The really interesting thing, is that it does work, and some of them could have plated small objects.

They do work because a basic battery requires nothing more than ordinary items. All you need are two different types of metal, and if placed in an electrolyte liquid, an electrical current will flow from one piece of metal to the other. A penny and a nickel in a bowl of vinegar will do. So they work in a way like you can turn a flower pot upside down and wear it as a helmet, or you can drink out of a shoe. The fact that something can be used as something else does not mean that it was ever intended that way.

The thing is that it would be the worst thing you could try and use for a battery: it would not last very long at all, and its electrolyte would need to be replaced quite often. However, it is sealed with asphalt, a thermoplastic, which would make it prohibitively inconvenient to refill.
Also, it lacks terminals. Batteries need a positive and a negative terminal that is accessible for connecting wires.
Also, ancient Egyptians did not know about wiring. Without wires, there was no way to get current out of the battery and to the theoretically powered device.

It's almost certainly just a scroll jar.