More on Hamilton’s crash
The 2008 world champion had done a few filming laps in the silver W04 on Monday, but Wednesday was his first real day of on-track work in the wake of his six years as a McLaren driver.
Briton Hamilton sped over the gravel at the end of the back straight, hitting the tire wall head-on.
A team spokesman said the cause was a braking problem.
"He managed to slow the car with the front brakes but was unable to avoid the barrier. Lewis is fine," he said.
It is another blow to Mercedes, after Nico Rosberg's debut running on Tuesday was cut short by an electrical fire.
"This is really annoying," chairman Niki Lauda is quoted by Auto Motor und Sport.
"Yesterday we lost almost the whole day of testing, today again …"