Guess it depends which brand/OEM locomotive...know most of the GE diesel/electric locomotive have huge batteries
Did you guys know that the Submarines of WWII were diesel/Electric and ran on battery power when submerged ?? Huge batteries of that era
Yes, many of the other OEMs used large resister grids to dissipate the regenerated power during regenerative braking....most of the 'variable speed' electric controllers employed resister grids before the late 1960's and into the early 1970's and is when my startups made money converting them to solid state variable speed controllers