Green’s Dictionary of Slang

to smoke marijuana.

1956		C. MacInnes ‘A Short Guide for Jumbles’ in England, Half Eng. (1960) 27: Coloured addicts [...] make the same sort of distinction between those who ‘charge’ (smoke hemp) and those who ‘pop’ (inject heroin and so on).
1988		S. Selvon Eldorado West One 80: He has been charging up on some reefers.