ŝargi

One hat apart, and two different words. This is the trap of the band. Ŝargi and ŝarĝi differ by the circumflex on the g, and in the x-system they are sxargi and sxargxi, which is two letters. They are separate roots with separate dictionary entries, and the division between them is clean once you hear it.

Ŝarĝi is about weight. You put on something that has to be carried: a cart with goods, an animal with a load, a person with responsibility. Ŝarĝo is the burden, and the word goes figurative easily.

Ŝargi is about supply. You put in something the thing needs in order to work: a gun with a cartridge, a camera with film, a battery with electricity, a phone with a charge. Ŝargo is the charge in that sense, and malŝargi is to unload a weapon or to discharge a battery.

So a lorry is ŝarĝita and a phone is ŝargita, and if you swap them you have said that the lorry is powered up and the phone is heavy. English hides the distinction behind one word, charge, that does both jobs and several others.

Both come from the same French verb charger, which is the neat part: one etymology, deliberately split into two roots so that Esperanto never has to be ambiguous where English is. Compare logi and loĝi, the other pair in this course separated by nothing but a circumflex, and be equally careful when you type without diacritics.