I'm betting the mines at Minas Gerais are enough to bring the Carthaginians back. There's nothing like them in the coastal stretch of Africa that the Carthaginians control and eventually Britain and Spain will be lost to them.
I do imagine that they'll eventually figure out the trade winds phenomenon. the editors of the Periplus of Hanno the Navigator suggested that Hanno employed both the Canarian current and the north-east trade winds in his trip along the coast of Africa. As I've described the situation, they've been picked up by the Brazil Current and dumped in Brazil - this happened to a certain Jean Cousin of Dieppe, in 1488, who was allegedly dropped near the mouth of the Orinoco. Once deposited unceremoniously in Brazil, their natural instinct would lead them to hug the coast, I think; the South Connecting Current would pull them southwards, and eventually bring them in contact with the winds heading back west.
Will they discover the Equatorial Current and the Gulf Stream? I would imagine they would. The Carthaginians would continue exploring, I think; their maps were the envy of the ancient world (our own word, map, is probably derived from Phoenician *mappē (< CS *manpay) which means something like a cheesecloth, and came into the languages of Europe via Latin mappamundī). I don't imagine they'd be content with what they have, and eventually they'd venture north and south of the regions serviced by the South Atlantic trade winds - this time hugging the coast, of course.
The advantage of the Brazil Current is that it can easily be concealed from the Romans - it is far down the coast of Africa, in territory completely unknown to them, and their approach to it is blocked by the Carthaginians themselves. The Equatorial Current is less easily concealed.