The man accused of making bombs to attack London's transport network on 21 July 2005 did not intend to hurt anyone, a jury has heard.
Mr Ibrahim is accused of trying to detonate a bomb on a bus
Muktar Ibrahim, 29, conducted tests on hydrogen peroxide and chapatti flour mixtures to ensure they would only go "pop", Woolwich Crown Court was told.
His lawyers said each of the devices was "constructed so as not to detonate" and were not capable of detonation.
Mr Ibrahim and five others deny conspiracy to murder.
All six also deny conspiracy to cause explosions.
George Carter-Stephenson, QC for Mr Ibrahim, said his client had made the devices in a north London flat - said to be the home of another defendant, Yassin Omar.
"The defendant conducted tests to ensure to the best of his knowledge and belief that the devices would only make a popping sound and would act in the manner in which they acted on July 21."
Mr Ibrahim, from Stoke Newington in north London, is accused of trying to detonate a rucksack bomb on a bus.
The prosecution said it was part of an extremist Muslim plot to carry out a series of explosions on the London transport system.
Manfo Asiedu, Hussein Osman, Ramzi Mohammed and Adel Yahya are also accused of taking part in the plot.
The trial continues.