At sea bound for Derry again on her fifth voyage, on 3 May 1944 Donnell made a sound contact, then sighted a periscope a few minutes later and pressed home a depth charge attack on U-473.

Arriving after a 300-mile dash in response to a call from Donnell, an 18-hour hunt by the 2nd Support Group under Captain Frederic John Walker began which brought U-473 to the surface, where she was sunk by gunfire.

Since Donnell had a large turbo-electric generator, but was not able to sail by herself because of the damage she had sustained, the ship was converted to an electric power barge and reclassified IX-182 on 15 July 1944.

Donnell was towed to Plymouth, England, in July to embark passengers, take on cargo, and have electric power cables installed in place of her torpedo tubes.

In February 1945 she was returned to England, and served as barracks ship at Portland and Plymouth until towed back to the United States, arriving at the Philadelphia Navy Yard on 18 July 1945.