 The ships ' turbines were equipped with Föttinger gears , which significantly improved performance at cruising speeds and provided a corresponding increase in range of about 20 percent . The vessels were designed to store 800 t ( 790 long tons ) of coal and 250 t ( 250 long tons ) of oil in purpose @-@ built storage spaces ; the hull areas between the torpedo bulkhead and the outer wall of the ship were used to store additional fuel . Maximum fuel capacity was 4 @,@ 000 t ( 3 @,@ 900 long tons ) of coal and 2 @,@ 000 t ( 2 @,@ 000 long tons ) of oil . This was estimated to give a range of up to about 8 @,@ 000 nautical miles ( 15 @,@ 000 km ; 9 @,@ 200 mi ) at a cruising speed of 14 kn ( 26 km / h ; 16 mph ) . Electrical power on the vessels was provided by eight diesel generators that put out 2 @,@ 320 kilowatts at 220 volts . 
