"You have a price action increasing so the actual value of the stock is going up, but the momentum indicators are coming down."
"It’s known as negative divergence," Mayne added, "so you can see that the last recent high is higher than the last one."
Mayne said BHP had had "a tremendous run recently", but warned that run was on its last legs.
"It looks like we might be in the last six months of the run on BHP Billiton, … it's just a bit of an early warning sign that if you are trading very long term, any up moves that could break this high, it’s probably time to get your chips off the table,” he said.
"That doesn’t mean BHP Billiton is suddenly going to crash and suddenly fall 15-20 percent from here, but what one can expect from this situation is a move back to the 200 simple moving day average," said Mayne.