In 1924, four steam railcars of the Bavarian type MCCi were taken to the Fuchs wagon factory in Heidelberg to be converted there into electric railcars with BBC drive technology. Since the vehicles lived up to expectations, another 32 were purchased between 1927 and 1933 as new builds and designated ET 85.
Although electric propulsion required less space than the steam engine, the equipment of the time was still too bulky to be installed under the floor. The transformer and tap changer were located in a machine room which, for safety reasons, was only accessible from the outside through a door. Power was provided by two nose-suspended motors, each with an hourly output of 250 kW, in the bogie that was located under the engine room. Analogous to the MCCi and Bavarian local trains in general, the ends initially had gangway doors, but these were later removed. The motor cars were completed by the ES 85 control car, which had a luggage compartment instead of the engine room. 34 control cars were purchased for a total of 36 motor cars. In addition, there were converted three-axle passenger cars, which served as trailers designated EB 85. 70 of these were purchased. This meant that most of the vehicles could run as a four-car set consisting of one motor car, two trailers and one control car.
The vehicles were used not only on the Munich suburban lines as originally planned, but also on the Dreiseenbahn in the Black Forest and on the Wehratalbahn. For longer overland routes, two vehicles were delivered with a modified gear ratio that allowed 100 instead of 75 km/h. After the war, the Bundesbahn took over all of the examples and continued to use them on the traditional routes. Three pieces were rebuilt in 1949 with a shorter gear ratio for steep sections and designated as ET 90. These only reached 50 km/h. From 1968, the motor cars were designated as class 485 and the control cars as class 885. The three ET 90s accordingly became class 490. The latter were phased out by 1972, the remaining vehicles by 1977.