[1] The prototype at Cherbourg was successful enough that Navy Minister Gaston Thomson opened a competition for submarines that were faster on the surface and with longer range than the preceding Pluviôse class on 6 February 1906.

Like most French submarines of this period, Charles Brun was fitted with a prominent "walking deck" above her single hull to facilitate operations on the surface.

Externally, the boat was equipped with two rotating Drzewiecki drop collars below the "walking deck" and two fixed launching frames at the stern aimed to the rear.

Initial testing of her powerplant was plagued by combustion problems that sent a lot of smoke and flames out the funnels, but these were resolved before the submarine began her sea trials on 1 June 1911.

The submarine made her deepest dive (25 m (82 ft)) on 10 October and operation of the powerplant and her habitability underwater was judged acceptable.

Even using the electric motors, her underwater endurance could not be extended beyond about three hours because the Maurice boilers worked best when used at a high rate in a relatively short period.

[3] The Navy's Test Commission (Commission permanent d'Essais de la Flotte) assessed Charles Brun as unsuitable for active service with the fleet after her trials were concluded in August 1913 and began condemnation proceedings on 20 October after rejecting a proposal to replace the forward boiler with batteries taken from a decommissioned Naïade-class submarine.

Beginning in January 1914, her hull was stripped of most of her equipment, her engines were reused in the gunboat Espiègle, and then ballast was added so it could be used in testing floating drydocks.

When the First World War began in August, her conversion into a water tank for the naval base in Bizerte, French Tunisia, was proposed, but could not be performed because of stability issues from the earlier work.